Nuclear Energy

INTRODUCTION: WHAT IS NUCLEAR ENERGY?

Nuclear energy is energy that can be released from the nucleus of an atom. There are two ways to produce this energy, either by fission or fusion. Fission occurs when the atomic nucleus is split apart. Fusion is the result of combining two or more light nuclei into one heavier nucleus. Most often, when people discuss nuclear power, they are talking about nuclear fission. Power production from fusion is still in its infancy.

Atoms are made up of several parts: protons, neutrons, electrons, and a nucleus. A nucleus is the positively charged center of an atom. Protons are positively charged particles, and neutrons are uncharged particles. Electrons orbit around the nucleus and are negatively charged. Fission can occur in two ways—first, in some very heavy elements, such as rutherfordium, the nucleus of an atom can split apart into smaller pieces spontaneously. With lighter elements, it is possible to hit the nucleus with a free neutron, which will also cause the nucleus to break apart.

Either way, a significant amount of energy is released when the nucleus splits. The energy released takes two forms: light energy and heat energy. Radioactivity is also produced. Atomic bombs let this energy out all at once, creating an explosion. Nuclear reactors let this energy out slowly in a continuous chain reaction to make electricity. After the nucleus splits, new lighter atoms are formed. More free neutrons are thrown off that can split other atoms, continuing to produce nuclear energy. The first controlled nuclear reaction took place in 1942.

Nuclear fission

Since at least the 1920s, scientists had believed that it might someday be possible to produce energy by splitting atoms. They based this belief on their growing understanding of the physics of the atom. They knew that atoms contain energy, and they believed that by "splitting" the atom, or breaking it apart, they could release that energy. The process would come to be called nuclear fission.

An atom is made up of three kinds of particles: neutrons, protons, and electrons. Two of these particles, neutrons and protons, are found in the nucleus, or center, of an atom. A neutron does not have an electrical charge. It is called a neutron because its electrical charge is neutral. A proton has a positive electrical charge. Circling around the nucleus of an atom in layers are electrons, which have a negative electrical charge. To keep the overall electrical charge neutral, an atom has to have the same number of protons and electrons. Positive and negative electrical charges attract each other. The charges bind the particles of an atom together. When an atom is split, some of this energy is released.

Words to Know

Critical mass

An amount of fissile material needed to produce an ongoing nuclear chain reaction.

Decay

The breakdown of a radioactive substance over time as its atoms spontaneously give off neutrons.

Enrichment

The process of increasing the purity of a radioactive element such as uranium to make it suitable as nuclear fuel.

Fission

Splitting of an atom.

Fusion

The joining of atoms to produce energy.

Meltdown

Term used to refer to the possibility that a nuclear reactor could become so overheated that it would melt into the earth below.

Pile

A mass of radioactive material in a nuclear reactor.

The atoms of different elements have different numbers of particles. Some elements are very simple and light. Hydrogen is the simplest and lightest element because it has only one proton, one electron, and no neutrons. In contrast, the heaviest element in nature is uranium. (Some heavier elements have been artificially produced in laboratories, but these elements do not exist in nature.) Uranium atoms contain ninety-two protons and ninety-two electrons. The number of neutrons can vary, depending on the isotope of uranium under consideration. An isotope is a "species" of an element. It contains a different number of neutrons from other isotopes of the same element. Generally, uranium nuclei contain either 143 or 146 neutrons.

For nuclear energy, uranium is the most important element. Uranium is used as fuel to produce nuclear reactions. It makes a good fuel source because uranium atoms are so big and heavy. They are easier to break apart. These large atoms can be thought of as a house built with playing cards. The house becomes increasingly unstable as cards are added, and is more likely to fall apart the bigger and heavier it gets. In a nuclear power plant, the goal is to create fission from uranium fuel and to be able to speed the reaction up (or slow it down) to control the amount of energy being produced.

HISTORICAL OVERVIEW: NOTABLE DISCOVERIES AND THE PEOPLE WHO MADE THEM

Scientists such as Enrico Fermi (1901–1954) noticed that the free neutrons in elements such as uranium bombard other uranium atoms. This bombardment causes the other atoms to split and release additional neutrons. These additional neutrons then bombard other atoms. The process continues in a chain reaction, or a reaction that keeps going on its own. A neutron in this way can be thought of as similar to a cue ball on a pool table. The cue ball bombards the cluster of balls at the other end of the table, causing the cluster to break apart. All the balls then bounce around, bumping into one another, causing further collisions, and so on.

Spontaneous Fission

Some elements, including uranium, undergo fission spontaneously, or on their own, as neutrons break away from the atom. These elements are said to be radioactive because they release subatomic particles and energy. This spontaneous fission is generally a very slow process. Scientists use the word decay to refer to the breakdown of a radioactive substance over time as it releases its neutrons.

Fermi had conducted experiments in nuclear fission in 1934 while he was still living in Rome, Italy. He had bombarded uranium with neutrons and discovered that what was left over afterwards were elements that were much lighter than uranium. This led him to believe that the uranium atoms had been split. The mass number of the leftover elements was smaller, so the uranium must have transformed into different elements as it broke down. In 1938 German scientists Otto Hahn (1898–1968) and Fritz Strassman (1902–1980) conducted a similar experiment. They discovered that what was left over after bombarding uranium with neutrons

The Periodic Table of the Elements

Elements are the fundamental building blocks of nature. Each box in the Periodic Table of the Elements provides basic information about the size and weight of each element. It arranges the elements from lightest to heaviest. It also arranges them into families that share some important characteristics. Each element has a name and a chemical symbol. In the case of uranium, the symbol is simple, U. The symbols for some elements seem strange. The symbol for lead, for example, is Pb because the symbol is taken from the Latin word for lead, plumbum.

The periodic table also contains each element's atomic number and atomic weight. The atomic number is found in the upper left-hand corner of the element's box. It specifies the number of protons in the element's nucleus. Thus, it is equal to the number of electrons. The atomic number for hydrogen is 1, for uranium, 92.

At the bottom center of each box is the element's atomic weight. Atomic weight is a little more complicated. Basically, it represents the combined total of protons and neutrons in the nucleus, called the mass number. But the atomic weight of uranium is given as 238.02891 rather than just 238. The reason for the digits to the right of the decimal point is that many elements, including uranium, occur in different isotopes.

Uranium, for example, has sixteen different isotopes, though only three are found with any frequency. These isotopes are U₂₃₄, U₂₃₅, and U₂₃₈. (Sometimes scientists write these differently, as ²³⁴U and so on or U-234.) While the number of protons and electrons in a given element is always the same, the number of neutrons can vary, producing different isotopes. This accounts for the different atomic weights (234, 235, and 238 for uranium). For uranium and other elements, the odd digits to the right of the decimal point occur because on the Periodic Table scientists provide a weighted average of the different isotopes. Therefore, the number may not be a whole number. As a practical matter, the atomic weight figure can be rounded off to the closest whole number.

was the much lighter element barium. This experiment confirmed that the uranium atoms had split.

Other scientists such as Lise Meitner (1878–1968) from Austria and Niels Bohr (1885–1962) from Denmark arrived at similar results. But they also made a startling discovery. When the atomic weights of the by-products of their experiment were added together, something was missing. If every piece of a broken window is swept up and weighed, the total weight of the pieces should be the same as the weight of the original window. Scientists expected that the same principle would apply to atoms. If atoms broke down because of fission, the atomic weight of the new elements formed, when added together, should be the same as the atomic weight of the original uranium. But Meitner and Bohr found that the elements in the reaction lost mass. Some of the mass had changed to energy. In this way they proved the truth of the famous equation from Albert Einstein (1879–1955), E = mc². This equation says that energy (E) is equal to mass (m) multiplied by the speed of light (c) squared. Mass, or matter, could be converted into energy.

The Italian Navigator

In December 1942 a message was sent to a number of high officials in the U.S. government. The message was written in code because at the time, the United States was at war and the authorities wanted to keep the contents of the message secret. The message read: "The Italian navigator has just landed in the new world."

The "Italian navigator" was physicist Enrico Fermi. Fermi had left his native Italy for the United States in 1938 because he saw the storm clouds of World War II (1939–1945) gathering over Europe. "The new world" referred to the successful outcome of an experiment. The experiment was conducted by Fermi and a team of researchers at the University of Chicago. On December 2, 1942, in a squash court under the athletic stadium, Fermi oversaw the world's first controlled nuclear reaction. On that date, humanity did indeed land in a new world, the world of nuclear energy.

None of these experiments produced a chain reaction, or a continuing fissioning of atoms. However, in 1942 Fermi thought of a way to create such a chain reaction. He took 40 tons of uranium, a nuclear "pile," and surrounded it with 385 tons of graphite blocks to contain the uranium. (A "pile" of nuclear materials is not literally a pile. "Pile" refers to a quantity of nuclear materials in a nuclear reactor.) This would provide him with the "critical mass" needed to produce an ongoing atomic reaction.

Fermi's main concern was to make sure that the reaction did not get out of control. A controlled chain reaction produces a flow of energy, but an uncontrolled chain reaction produces an explosion. Fermi needed a way to make sure that he did not blow up Chicago by letting his planned reaction get out of control. The graphite blocks would help, but he also inserted rods made of cadmium, a soft bluish-white element, into the pile. Cadmium absorbs neutrons, so it can keep nuclear fission reactions under control.

Lise Meitner

Lise Meitner's contributions are often overlooked in the history of nuclear power development. As a woman, Meitner was barred from higher education in her native Austria until 1901, when she began studying physics at the University of Vienna. After she completed her doctorate in 1907, she worked with the famous German physicist Max Planck (1858–1947) and chemist Otto Hahn.

Meitner was born into a Jewish family. Although she had converted to Christianity, she was still driven out of Austria and Germany after the Nazi regime took power. She settled in Stockholm, Sweden, where she continued her work on radioactivity. There she worked with Hahn and Strassman. She and another physicist, Otto Frisch (1904–1979), actually coined the phrase "nuclear fission."

One of science's worst scandals took place in 1945. That year, Otto Hahn was given the Nobel Prize in Chemistry for the discovery of nuclear fission. The contributions of Lise Meitner were entirely ignored. While such names as Planck, Fermi, Hahn, Einstein, and others were famous in the scientific community, Meitner's name was largely forgotten. Later scientists acknowledged her important role, and in 1966 she was awarded the U.S. Fermi Prize in Physics.

On that December afternoon in 1942, Fermi and his team slowly pulled a few of the cadmium rods out of the pile. Now some of the spontaneously released neutrons in the uranium could bombard other uranium atoms. Each collision produced an average of 2.5 new free neutrons, which in turn bombarded other atoms, releasing 2.5 more free neutrons, and so on. More rods were slowly pulled out, and the pace of the reaction increased. When rods were pushed back in, the reaction slowed as the cadmium soaked up neutrons. Chicago did not blow up, and Fermi had created the world's first nuclear reactor.

From the Manhattan Project to Atoms for Peace

Fermi conducted his successful experiment almost exactly one year after the Japanese attacked the U.S. naval base at Pearl Harbor, Hawaii, on December 7, 1941. This event pulled the United States into World War II. The war had begun in September 1939, when German dictator Adolf Hitler (1889–1945) ordered his troops to invade Poland. In the years that followed, Germany occupied much of Europe. Meanwhile, the Japanese empire was spreading throughout Asia and the Pacific.

Most of the leading scientists involved in nuclear research were from Germany. U.S. policy makers learned that German scientists were trying to develop an atomic bomb, a bomb whose enormous destructive force would come from an uncontrolled fission reaction. Such a bomb in the hands of Germany could have changed the outcome of the war. Thus, American policy makers developed a plan for the United States to create such a bomb first. This is the reason for the secrecy surrounding the message informing the government that Enrico Fermi's experiment had been successful.

The World's First Nuclear Reactor

Enrico Fermi is credited with building the world's first nuclear reactor. Strictly speaking, this is only partially true. He actually built the first "artificial" nuclear reactor. In 1972 a team of French scientists came across an old mine in West Africa. Inside they found some uranium ore. In this ore they found concentrations of U₂₃₅ of 0.4 percent. But the concentration of U₂₃₅ in uranium ore found in nature is always 0.72 percent. By analyzing the trace elements in the ore, the scientists concluded that the amount of U₂₃₅ was less than normal because a chain reaction had occurred. In other words, a naturally occurring nuclear reactor had developed in the mine. The scientists estimate that the reaction occurred more than two billion years ago over a period lasting about 600,000 to 800,000 years.

The research program to develop the bomb was the Manhattan Project. (The name Manhattan has no particular meaning. The branch of the army that oversaw the project was based in Manhattan, New York.) Beginning in 1943, the nation's top scientists, many of them from top-ranked universities, came to Los Alamos, New Mexico. The brilliant physicist J. Robert Oppenheimer (1904–1967) directed the research. They worked in shacks and lived in primitive conditions, all the while keeping their work top secret.

Continuing the research of Fermi and others, the scientists succeeded in building an atomic bomb, which they tested in the New Mexico desert on July 16, 1945. By this time, though, Germany had surrendered and the war in Europe was over. The war continued to rage in the Pacific as the United States and its allies fought the determined Japanese empire. During the final months of the war with Japan, both countries lost large numbers of troops in bloody island battles, such as those on the Japanese island of Iwo Jima. The Japanese were defeated, but the nation refused to surrender. To put a quick end to the war, the United States released an atomic bomb over the Japanese city of Hiroshima on August 6, 1945. A similar bomb destroyed Nagasaki three days later. Together, the two bombs immediately killed over one hundred thousand people, and many more would later die as a result of burns and radiation sickness. Faced with such a destructive weapon, the Japanese finally surrendered.

The decision to use the atomic bomb was highly controversial. Many U.S. policy makers urged use of the bomb as a way to save the lives of U.S. (and Japanese) troops, who faced the possibility of a difficult invasion of Japan. Others, including many nuclear scientists, believed that using the bomb would cause too much destruction and death. Many believed that it was just a matter of time before Japan would surrender.

After the Soviet Union developed its own atomic weapons, the world's two superpowers began to stockpile them. They accumulated far more nuclear weapons than would ever be needed to defeat the other side. In the 1950s and beyond, the world lived in fear that a nuclear war would erupt, with devastating consequences. Scientists, though, searched for peaceful ways to use nuclear energy. On December 8, 1953, U.S. president Dwight D. Eisenhower (1890–1969) addressed the United Nations. In his speech, he outlined the "Atoms for Peace" program. He suggested that atomic development and research be turned over to an international agency and that research be conducted to find peaceful uses for atomic energy. This speech gave a major push to efforts to harness atomic energy for the benefit of humankind rather than as a weapon.

Atomic energy development

Those efforts had already begun in the United States. In 1946 the government created the Atomic Energy Commission. Its job was to oversee the development of nuclear power. One of its first steps was to authorize the development of Experimental Breeder Reactor I in Arco, Idaho. On December 20, 1951, the reactor produced the world's first electricity fueled by nuclear power, lighting four 200-watt light bulbs. On July 17, 1955, Arco, home to one thousand people, became the world's first town to be powered by nuclear energy.

Until this time, nuclear energy had been firmly under the control of the military. The first civilian power plant began operating in Susana, California, on July 12, 1957. The world's first commercial-sized nuclear power plant reached full operating power in 1957 in Shippingport, Pennsylvania. (Most nuclear power plants, for safety reasons, operate at about 70 to 90 percent of their maximum capacity.) Meanwhile, on July 14, 1952, the keel had been laid for the world's first nuclear-powered submarine, the Nautilus. On March 30, 1953, the sub powered up its nuclear generators for the first time.

Nuclear power developed rapidly in the late 1950s and into the 1960s. On October 15, 1959, the Dresden-I Nuclear Power Station came online (that is, began to operate) in Illinois. This was the first nuclear power plant to be built entirely without money from the government. On August 19, 1960, the Yankee Rowe Nuclear Power Station in Massachusetts became the nation's third nuclear power plant. On November 22, 1961, the U.S. Navy commissioned the U.S.S. Enterprise, the world's largest ship. Powered by nuclear energy, the aircraft carrier could operate at speeds up to 30 knots for as far as 400,000 miles (740,800 kilometers) without having to refuel. Another milestone was passed on December 12, 1963, when the Jersey Central Power and Light Company launched construction of the Oyster Creek nuclear power plant. This was the first nuclear plant to be ordered as an economic alternative to a fossil-fuel plant.

By 1971 the United States was operating twenty-two nuclear power plants that provided 2.4 percent of the nation's electricity. By the end of the 1970s, seventy-two plants were producing 12 percent of the nation's electricity. And by the end of the 1980s, 109 power plants were generating 14 percent of the nation's electricity. These numbers peaked in 1991, when the number of plants rose to 111, together supplying about 22 percent of the nation's electricity. By the early 1990s nuclear power plants were generating more power in the United States than all power sources combined generated in 1956.

Similar developments were taking place worldwide. As of late 2005, 441 nuclear reactors were producing 2,618.6 billion kilowatt-hours of electricity in thirty countries. The United States led the way with 103 nuclear reactors still in operation. Other countries with a large number of nuclear reactors included Canada (18), France (59), Germany (17), Japan (55), Russia (31), and the United Kingdom (23). The country that generated the highest percentage of its electricity needs from nuclear power was France, at 78 percent. Close behind was Lithuania, whose one power plant generated 72 percent of the nation's electricity.

Setbacks

In the 1950s and 1960s scientists around the world believed that nuclear power had unlimited potential. Along with most of the public, they believed that nuclear plants would provide an endless source of cheap, renewable, clean energy. Yet by late 2005 only thirty-nine new nuclear power plants had been proposed by the nations of the world, and none were proposed for the United States. The percentage of electricity produced worldwide amounted to just 16 percent. The nuclear energy industry seemed to be stagnating (standing still; not moving forward).

Throughout the 1980s and 1990s and into the new millennium, the public began to have serious doubts about the safety of nuclear power. Those doubts arose because of the industry's first major setback, which took place on March 28, 1979. On that day an accident occurred at the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania. No one was injured or killed, and no one was overexposed to radiation from the plant. Still, the accident shut the plant down. If the accident had not been contained, a meltdown could have occurred. ("Meltdown" refers to an out-of-control reaction that overheats the reactor, causing it potentially to melt into the earth below, releasing radiation into groundwater and the atmosphere.) Many Americans started to distrust nuclear power, believing that the possibility of a catastrophe was too great. Not helping the industry was a major movie that year called The China Syndrome. The movie dramatized events at a fictional California nuclear power plant that were eerily similar to the Three Mile Island accident. Its title referred to the theoretical possibility that an overheated nuclear reactor could melt its way through the Earth to China.

Then in 1986 a major disaster struck. On April 26 an explosion took place in reactor number 4 at the nuclear power plant in Chernobyl, a city in Ukraine (formerly part of the Soviet Union) about 70 miles (112 kilometers) north of Kiev. In this accident, a large amount of radiation was released into the atmosphere. Scientists estimate that the amount of this radiation was 100 to 150 million curies (although this unit is well known scientists now use the Bequerel as the unit of radiation), primarily in the form of radioactive cesium and iodine. Thirty-one people were killed in the accident, including firefighters, and 135,000 people within a 20-mile (32-kilometer) radius had to be permanently evacuated. Several years later, an additional 110,000 people were evacuated. Entire villages had to be decontaminated, and in the years that followed the rates of certain cancers among people in the area were noticeably higher. (Exposure to radiation increases the risk of developing cancer.) Radioactivity spread over large areas of the Soviet Union, into Eastern Europe, and as far away as Scandinavia. It is estimated that the accident cost the Soviet Union $12.8 billion. The human costs—stress, lost homes, poor health—cannot be measured.

These accidents burst the nuclear industry's bubble. People began to fear a major accident that would dwarf the kinds of accidents that took place at conventional coal-fired electric-generating stations. On December 16, 2005, the world held its breath when a large explosion damaged a Russian nuclear power plant outside the city of St. Petersburg.

Measuring Radiation

In measuring radiation and radiation exposure, physicists use a number of units of measurement, depending on exactly what they are trying to measure. Complicating matters is that there are "common units" of measurement and so-called "SI units," or "standard units." SI units are those recommended by the worldwide General Conference of Weights and Measures. Some of these units, such as curies (named after French physicists Pierre [1859–1906] and Marie [1867–1934] Curie) measure amounts of radiation. Others, such as rems, measure doses of radiation people might receive.

The nuclear industry began to face other problems in the 1980s and beyond. The cost of building nuclear power plants was spiraling out of control. Most new plants went far over budget. Also in the 1980s and 1990s, the first aging nuclear plants had to be shut down and taken out of operation. It was discovered then that the cost of decommissioning (shutting down) a nuclear power plant was high because extreme care had to be taken to dispose of radioactive components properly. On top of these problems, the waste from nuclear power plants was beginning to accumulate, and no one knew quite what to do with it.

Because of these problems, plans for construction of new plants were in many cases canceled. By 2005 the number of operating plants in the United States had declined (to 103) as older plants were decommissioned. Nuclear power had become an emotional issue. Its supporters believe that by the year 2050, the energy needs of the United States will triple. They believe that other forms of alternative energy can help, but only nuclear plants can provide power on a large scale. Opponents of nuclear power, however, believe that the costs and the risks are too high.

HOW NUCLEAR ENERGY WORKS

Generating electricity through nuclear power is an enormously complex technical feat. It takes the combined skills of geologists (scientists who study Earth's structure, especially rocks), mine operators, engineers, and scientists, as well as large numbers of highly trained and skilled plant operators. The federal government oversees the construction and operation of these plants to make sure that they are built and operated to the very highest standards.

Uranium

Producing nuclear power begins with the fuel, uranium. Uranium was discovered in 1789 by a German chemist, Martin Klaproth (1743–1817). He discovered uranium in a mineral called pitchblende. The element was named after the planet Uranus, which had been discovered just eight years earlier. Scientists' best guess is that uranium was formed in supernovas (or exploding stars) about 6.6 billion years ago. In the Earth, radioactive decay of uranium is the planet's main source of internal heat.

Uranium is used primarily in the nuclear industry, but it has other uses as well. Because it is a dense, heavy element (18.7 times as dense as water), it is sometimes used in the keels of boats as a weight to keep them upright. (Density refers to weight relative to volume. A ton of feathers weighs as much as a ton of lead, but because lead is denser than feathers, it takes up far less volume.) Its density also makes it useful as a counterweight in such applications as airplane rudders, and it makes a good radiation shield.

The uranium atom

Uranium is the heaviest naturally occurring element. It has sixteen different isotopes, although the most common ones are U₂₃₅ and U₂₃₈. U₂₃₄ is found in trace amounts and results from the decay of U₂₃₈. The more abundant isotope, U₂₃₈ (which accounts for 99.3 percent of the uranium in the Earth's crust) plays a role in keeping the Earth warm. Like any radioactive substance, U₂₃₈ decays, but it decays very slowly. Its half-life is about the same as the age of the Earth, 4.5 billion years. ("Half-life" is a term scientists use to refer to the rate at which a radioactive substance decays, or breaks down. Thus, half of all U₂₃₈ has broken down over the past 4.5 billion years. Half of the half that is left will break down over the next 4.5 billion years, and so on.) From the standpoint of nuclear energy, the important isotope of uranium is U₂₃₅.

The nucleus of a U₂₃₅ atom consists of ninety-two protons and 143 neutrons. This is the isotope of uranium whose atoms can be split relatively easily. When a U₂₃₅ atom is struck by a neutron, the atom splits, releasing energy. It also releases two or three neutrons of its own, which in turn split other atoms, and on and on in a chain reaction. In a nuclear reactor, the released energy is at first kinetic energy. Kinetic energy is the energy contained in anything (such as water, wind, or a neutron) that is in motion. But submicroscopic particles travel only tiny distances, so the kinetic energy is rapidly converted to heat (similar to the way the brakes on a car get hot when they stop the kinetic energy of a moving car). This heat is then used to produce steam, which turns a generator to produce electricity. Heat makes up about 85 percent of the energy released. Most of the rest of the energy is in the form of gamma rays. (A gamma ray is a photon that is released by a radioactive substance. A photon is a form of energy, like light.)

In many respects, the process as described is much more complex. For example, physicists note that only isotopes with an odd number of particles in the nucleus, like U₂₃₅, are fissile (able to be split). Further, not every neutron that hits a uranium atom causes fission. Sometimes the neutrons are absorbed by the atoms they strike, so no fission takes place. Other neutrons simply escape and do nothing. Another complication has to do with the speed of the neutrons. Some are called "prompt neutrons," but others experience a delay of up to 56 seconds.

The challenge for nuclear engineers is to keep the ongoing fission reaction in precise balance. When the reaction is in balance, scientists say that it has reached "criticality." At criticality, the neutrons are doing their work in balance, meaning that their numbers remain constant and under control. The pace of the reaction can be speeded up or slowed down by increasing or decreasing the number of neutrons. If the increase is too rapid, the reaction can almost instantaneously get out of control.

Plutonium

Plutonium (chemical symbol Pu), named after the planet Pluto, is an element that forms in a reactor core as the isotope Pu₂₃₉. It forms when U₂₃₈, which is also present in nuclear fuel, absorbs a neutron. Now the atom has an odd number of particles in the nucleus, making it fissile in the same way that U₂₃₅ is. But like U₂₃₅, it sometimes just absorbs the neutron, creating the isotope Pu₂₄₀, which is not fissile. Over time, the amount of Pu₂₄₀ builds up in the fuel rods. When the rods are "spent," or no longer usable as fuel, this plutonium can be recycled. It undergoes a conversion process that makes it usable as nuclear fuel. Not all nuclear reactors are designed to allow this recovery and conversion process. Those that do are called "breeder reactors," for they "breed," or produce, additional fuel.

Plutonium is perhaps the most highly toxic substance that exists. The smallest amount can cause such diseases as lung cancer. Workers who handle plutonium observe the strictest safeguards to avoid exposure.

Uranium: From the ground to the reactor

While uranium can be found in seawater, it is found most commonly in rocks and is as common as the elements tin and gold. It exists in concentrations of about two to four parts per million. Uranium is mined in at least two ways. One is to dig up the ore that contains it, crush the ore, and then treat it with acid, which dissolves the uranium to remove it from the ore. The other is a process called in situ leaching (in situ is Latin for "in place"). In this process, the uranium is dissolved from rock and pumped to the surface of the Earth. Either way, the end result is a compound called uranium oxide, or U₃O₈. This material is often referred to as "yellowcake."

The uranium, though, cannot be used as fuel in this form. It first has to be "enriched," so mine operators sell the yellowcake to uranium enrichment plants. The first step in converting it into a usable fuel is to convert it into a gas, uranium hexafluoride, or UF₆. This increases the amount of uranium from its natural level of 0.7 percent to 3 to 4 percent, so the uranium is said to be "enriched." The next step is to convert the uranium hexafluoride to uranium dioxide, or UO₂. Uranium dioxide can then be processed into pellets that are about the size of a knuckle on a person's finger. The pellets are then inserted into thin, 12-foot-long (3.5-meter-long) metal tubes, called fuel rods. Bundles of these tubes are then inserted underwater into the core of the nuclear reactor.

Inside the reactor

A nuclear power plant has been constructed, probably at a cost of anywhere from $3 billion to $5 billion, or even more. Construction of the plant took at least four years, possibly up to ten years. Geologists have carefully considered the site of the plant to make sure that the chances of it being damaged by an earthquake or volcanic activity are small. Engineers and construction workers have carefully built the plant. The materials used were of the highest standards. Every weld in metal components was closely examined and even x-rayed to be sure it is as close to perfect as possible. Provisions were made to ensure that the plant is secure, so that terrorists or others cannot enter and take it over. Provisions have also been made for the safety of the plant's employees so they can quickly shield themselves from radiation in the event of an accident. The plant is built with "redundant," or repetitive, safety systems, so that if something breaks down, there is a backup. The most critical of these systems is water that can be used to cool an overheated reactor. No detail is overlooked.

As the time approaches for the plant to come online and begin producing power, the fuel is inserted into the tubes and the tubes, up to 200 of them, are inserted into the reactor core. Then, at the appropriate moment, the control rods are slowly pulled out. These rods are generally made of graphite or boron, and they control the pace of the nuclear reaction by absorbing neutrons. The farther the rods are inserted, the more neutrons they absorb, slowing down or stopping the reaction. As they are withdrawn, more and more neutrons make it to their target, and the chain reaction begins.

At this point the plant is nowhere near ready to operate at maximum power output. For weeks, the plant's engineers will fire up the reactor very slowly. They will check and recheck every component of the plant to make sure that everything is operating properly and safely. After a period of several weeks of testing, the reactor will begin producing power at its normal operating level, and consumers will begin enjoying the benefits of the electricity it produces.

CURRENT AND FUTURE TECHNOLOGY

Nuclear power plants come in many different shapes and designs. Many of the first plants to be constructed were huge, enabling them to produce the greatest amount of power possible. More recent designs are smaller, making them less costly and easier to build. But despite their many technical and engineering differences, nuclear reactors come in two basic types: pressurized water systems and boiling water systems.

Pressurized water reactor system

One system in common use is called the pressurized water reactor system. It is given this name because it relies on water under pressure to produce the heat needed to produce electricity. In such a system, the fuel rods are inserted into a steel pressure tank that contains ordinary water. The water acts as a coolant, but it also moderates the reaction because it can absorb neutrons. Protruding (sticking out) through the lid of the pressure tank are the control rods.

As the control rods are slowly pulled out, the chain reaction begins. The reaction produces heat, which heats the water in the pressure tank. The water heats to 518° Fahrenheit (270° Celsius). The water does not boil, though, because it is under intense pressure.

The heated water is then channeled to a heat exchanger in a closed circuit. The water in the heat exchanger is then heated up, producing steam. The steam drives a turbine generator that is little different in principle from a turbine used in a windmill or a hydroelectric dam. As the generator turns, it produces electricity. Meanwhile, the steam is condensed, usually by cool water from a lake or river, and returned to the heat exchanger.

Boiling water reactor system

The other major system, the boiling water reactor system, is more efficient than the pressurized water system. One noticeable difference is that with a boiling water system, the control rods protrude from the bottom of the containment chamber. Inside the chamber is the reactor core. The control rods are at the bottom because the water inside the chamber is allowed to boil. The steam created by the boiling water is allowed to rise to the top of the chamber. Pipelines carry the steam directly to the turbines, where its heat causes them to turn to create electricity. The steam then condenses and is channeled back into the containment chamber. Underneath the reactor is a circular tunnel filled partway with water. This tunnel is a safety mechanism. If any steam or water were to escape from the containment chamber, it would fall into the tunnel, where it could do no immediate harm.

The possibility of nuclear fusion

Scientists look forward to the discovery of a power source that is clean, safe, universally available at all times to all people throughout the world, and that uses a fuel that is abundant, cheap, and efficient. It would not contribute to global warming or air pollution, require large plants that would disrupt the natural environment, or produce dangerous by-products. To that end, some scientists conduct research into what is called "cold fusion." Cold fusion uses fuel that is commonly available from the hydrogen in water. However, governments have favored a more conventional approach to fusion at extremely high temperatures. In 2005, Cadarache in France was chosen as the site for the International Thermonuclear Experimental Reactor. This will be built as a cooperative venture between the EU, U.S., Russia, China, Japan, and South Korea. This is a major step in the development of fusion as a potential large-scale source of electricity that will not contribute to climate change.

Nuclear fission refers to the splitting, or breaking apart, of atoms. Nuclear fusion, as the name suggests, involves the fusing, or joining together, of atoms. The light nuclei of two atoms bind together during nuclear fusion to form a single heavier nucleus. One example is the deuteron, a single particle formed by the combination of a neutron and a proton. When a deuteron or similar particle is formed, its mass is generally less than the total mass of the two original particles. The mass that disappears is released as energy. What appeals to scientists seeking to harness nuclear fusion is that such reactions occur in nature throughout the universe, particularly in stars. Fusion takes place in stars because of their high temperatures, up to 18,000,032° Fahrenheit (10 million° Celsius), possibly even hundreds of millions of degrees. The problem is that while such high temperatures can be found in the center of stars, including the Earth's sun, they do not occur naturally on Earth.

Despite the high temperature needed for fusion to occur, scientists have tried to reproduce fusion reactions on Earth. The process they formulated was to use two isotopes of hydrogen. These isotopes, called "heavy hydrogen" because they contain extra atomic particles, are deuterium and tritium. While a normal hydrogen atom consists of a single electron and a single proton in the nucleus, deuterium also contains one neutron in the nucleus and tritium contains two. These isotopes fuse at lower temperatures than do the nuclei of regular hydrogen atoms, and they are relatively abundant. In the oceans, about one in 6,500 or 7,000 hydrogen atoms are deuterium, and they can be easily extracted. The source of tritium is an element called lithium, which is abundant in the Earth's crust.

Scientists discovered that when a mixture of deuterium and tritium is raised to a high enough temperature, or when the elements are accelerated to a very high speed, one deuterium nucleus fuses with one tritium nucleus. The result is a new element, helium. More importantly, excess energy is given off in the form of a neutron that moves at a very high speed. Scientists believe that fusion could be the "fuel of the future" because the fuel—deuterium and tritium—contains an enormous amount of energy, called "density" by scientists. It has been estimated that a single thimbleful of heavy hydrogen contains the same amount of energy as 20 tons of coal. An amount that would fill the bed of a pickup truck would provide the same amount of energy as 21,000 rail cars full of coal or 10 million barrels of oil. Further, using such fuel would be extremely safe. The only by-product is helium, and there is no danger of a fusion reaction spinning out of control. If the fuel escapes, the fusion reaction simply stops.

So far, fusion experiments have failed to produce any power in excess of the power needed to produce the fusion reaction. In other words, there was a net power loss. For many scientists, the enormous energy demands of hot fusion make it impractical. Instead, they have searched for a way to create fusion reactions at low temperatures, called "cold fusion." Cold fusion is a term coined in 1986 by Dr. Paul Palmer of Brigham Young University in Utah. It is the popular term for what scientists call "low energy nuclear reactions" in a field that is sometimes called "condensed matter nuclear science."

In 1984 two scientists, Stanley Pons of the University of Utah and Martin Fleischmann from England's University of Southampton, began conducting cold fusion experiments at the University of Utah. On March 23, 1989, Pons and Fleischmann made an announcement that startled the world. The two claimed that they had successfully carried out a cold fusion experiment. This experiment produced excess heat that could be explained only by a fusion reaction, not by chemical processes. Many scientists, though, disputed their claim. They tried to duplicate the Pons-Fleischmann experiment and failed.

So the question remains: Is cold fusion possible? Some scientists answer with a no. Many other scientists, though, disagree. They point out that cold fusion research is still just beginning. Some of the problems reported with duplicating the Pons-Fleischmann findings have been the result of normal uncertainties about how to design and conduct experiments to get consistent results.

Meanwhile, many scientists have made claims that they have produced cold fusion. Some of the most prominent researchers in the field are in Japan, where the level of funding for cold fusion research is much higher than it is in the United States. At Japan's Hokkaido University, for example, D. T. Munzo reported experiments in which the ratio of energy output to energy input was seventy thousand to one. As of 2005, though, the world seemed decades away from seeing a commercial fusion reactor, whether hot or cold.

BENEFITS AND DRAWBACKS

In the imaginations of many people, nuclear power plants are surrounded by a field of radiation. As they drive down the highway and see the characteristic cooling tower of a nuclear power plant rising on the horizon, some people feel a slight twinge of anxiety. They know that they are not being exposed to radiation, yet their emotions make them wonder whether maybe they are.

Supporters of nuclear energy dismiss these concerns. They argue that nuclear power plants are safe and that nuclear power offers many significant benefits. At the same time, nuclear power has significant drawbacks, particularly the potential for accidents, the problem of nuclear waste disposal, and the possibility that terrorists could attack nuclear power plants.

Benefits

The benefits of nuclear energy include the following:

1. Many scientists believe that nuclear energy remains the best way to provide large amounts of power for a large and growing world population. A typical nuclear power plant produces 1,000 megawatts, or 1 billion watts, of electricity. Other forms of alternative energy produce far less, particularly relative to their size. For example, the largest wind farm in the United States is the Stateline Wind Energy Center along the Columbia River on the Washington-Oregon border. This massive farm consists of 454 wind turbines, each 166 feet (50 meters) tall and, at peak capacity, generating 660 kilowatts, or 660,000 watts of power. Because of changing wind conditions, the windmills do not always operate at peak capacity. To provide power equivalent to that of nuclear power plants, immense numbers of large wind farms would have to be built.
2. Nuclear energy is reliable. In contrast to most other forms of alternative energy, nuclear energy can be provided on a consistent, predictable basis nearly anywhere in the world. It is not subject to weather conditions. In contrast, solar power requires consistent sunshine, so not all areas are suitable for solar power. Wind power has similar limitations. Hydroelectric dams provide large amounts of power worldwide, but the number of rivers that remain suitable for damming is limited. Such alternatives as ocean wave power and tidal power are likewise limited by geography and unpredictable weather patterns.
3. The supply of fuel for nuclear power is abundant. Uranium exists throughout the Earth's crust, although in some places, it can be mined more easily than in others. Scientists estimate that the amount of uranium known to be readily available is enough to last fifty years. However, they also point out that its relative abundance has not made it necessary for mining companies to search very hard for it. Scientists are confident that more intensive searching will yield abundant new reserves of uranium. While uranium is not renewable, as wind and solar power are, enough probably exists for many centuries to come. Further, nuclear plants produce plutonium as a by-product of the nuclear reaction. This plutonium can be reprocessed into fuel.

1. The price of nuclear fuel remains relatively constant, and its sources remain relatively consistent. Uranium is mined extensively in about twenty countries throughout the world. The relatively large number of suppliers ensures that prices do not change rapidly and unexpectedly. In contrast, the world's petroleum reserves are in the hands of a small number of countries. Many of these countries are politically unstable. As the Arab oil embargoes of the 1970s showed, oil supplies to the United States and other countries can be cut off overnight for political reasons. Uranium is not subject to these uncertainties, and nations such as the United States and Canada can mine their own uranium. In fact, Canada leads the world in uranium mining. Another leading producer is Australia, which, ironically, has no nuclear power plants.
2. Nuclear power plants have a low impact on the environment. A chief advantage of nuclear power is that it does not require the burning of fossil fuels such as coal. Thus, it is cleaner than fossil fuels and does not contribute to pollution.
3. Nuclear power plants are safe. As of late 2005 the only deaths that have ever resulted from a nuclear power plant accident occurred at the Chernobyl plant in Ukraine. Nuclear experts, though, note that the design of the Chernobyl plant was extremely outdated and that the plant was not very well constructed. This was a common problem for all types of construction under the Communist regime of the old Soviet Union. They believe that the kind of accident that happened at Chernobyl is much less likely with more modern and better built plants. This has meant that despite worries among the public, politicians have increasingly seen modern nuclear reactors as a source of energy that avoids emission of greenhouse gases and after a period where few reactors have been built they are being re-considered as energy sources.
4. With regard to safety, the track record of the nuclear industry has improved over the 1990s and early 2000s. For example, when something in the operation of a nuclear plant gets out of kilter, a "scram" takes places. This refers to a wide range of automatic safety mechanisms. Alarms sound, backup systems kick in if necessary, and the plant's controls automatically make necessary adjustments, particularly making sure that water surrounds the reactor core to keep its temperature under control. If necessary, the nuclear reaction stops and the reactor shuts down. The nuclear industry keeps track of the number of scrams per 7,000 hours of operation, or about one year. In the late 1990s two-thirds of U.S. nuclear power plants had zero scrams. The number of scrams at the other third was extremely low, and usually the problems that caused them were minor and easily fixed.
5. A major concern for nuclear plant workers is exposure to radiation. People are exposed to radiation every day of their lives. Radiation reaches the Earth from the sun, and it radiates from rocks in the earth. This radiation is referred to as "background radiation," and it varies with altitude (height above sea level) and geography. People in such countries as Finland are exposed to three times as much background radiation as Australians. Even on an airline flight over the North Pole from, say, Tokyo to London, people are exposed to cosmic radiation seven to eight times the normal level.

Drawbacks

Despite its many benefits, nuclear power has significant drawbacks as well. Throughout the 1990s and into the new millennium, scientists, environmentalists, and the public have focused more of their attention on these drawbacks. As a result, nuclear power has become an emotional political issue. Its opponents are passionate in their belief that nuclear power poses a significant danger to the world. Some of their concerns include the following.

Catastrophic accident

The potential for a catastrophic accident continues to exist. The world's nuclear power plants have accumulated a total of about twelve thousand years of operation. During that time, there have been only two significant accidents, Three Mile Island (although the public was not exposed to radiation during that accident) and Chernobyl. Supporters of nuclear power point out that far more people lose their lives in accidents at conventional power plants in one year than have lost their lives in nuclear accidents.

The problem is one of public attitudes rather than statistics. Opponents of nuclear power note that a catastrophic accident at a conventional power plant might be tragic for those injured and killed. Still, the effects would be limited to the plant itself and perhaps the immediately surrounding area. Deadly radiation would not be released into the atmosphere. People would not have to be evacuated, and those nearby when the accident occurred would not suffer the ill effects of radiation.

In contrast, a catastrophic accident at a nuclear plant could have enormous effects on the surrounding environment, effects that would last for decades, if not longer. Nuclear opponents believe that the risk is simply too great. One mistake, one faulty component, one operator error could create an environmental catastrophe. The margin for error is nearly zero. While the risk of a nuclear catastrophe is low, such a catastrophe would have high consequences.

Adding to the problem is the mysteriousness of anything nuclear. Ever since the atomic bombings of Japan at the end of the Second World War, people have been afraid of nuclear power. Excessive exposure to nuclear radiation can cause cancer, another word people respond to with fear. Few people understand nuclear physics. That sense of awe and mystery spills over into fear of anything "nuclear," including nuclear power plants.

Waste storage and disposal

Nuclear waste comes in two types: low-level and high-level. Low-level waste is produced by hospitals, which use radioactive materials for certain medical tests. Similar low-level waste is also used for research purposes at universities and other research facilities. This material has to be disposed of safely, and if it is done so, it poses little health risk to the public. The radioactivity in these materials breaks down quickly (usually in days or at most weeks), and the material can then be disposed of as normal trash.

Safety Stats

In 1998 the U.S. Bureau of Labor Statistics reported that for every 200,000 hours of work performed in nuclear plants, there were 0.34 accidents that resulted in injury. In contrast, for all other industries, the number was seven times greater, or 2.3 accidents per 200,000 worker hours.

High-level nuclear waste, such as that produced by nuclear power plants and in producing and dismantling (taking apart) nuclear weapons, is another matter. As of 2003 the United States had accumulated about 49,000 metric tons (a metric ton is about 2,200 pounds) of spent nuclear fuel rods. These are fuel rods that have been removed from power plants because the fuel is depleted. This amount would cover a football field to a height of 10 feet (3 meters). The U.S. Department of Energy estimates that the amount will total 105,000 metric tons by the year 2035. Much of this material is stored in water pools on the sites of nuclear power plants. No one knows what to do with this accumulating waste.

The problem with nuclear waste is the half-life of such elements as uranium and plutonium, as well as other radioactive materials produced in nuclear power reactors as by-products. Some of these by-products include cesium-137 and strontium-90, both highly radioactive. Most of these elements have extremely long half-lives. The half-life of plutonium is 24,000 years. The half-lives of some other radioactive elements are 100,000 years, even longer. This means that nuclear waste disposal has to be thought of in terms of geologic time, not next year or even next century. The ancient Roman Empire was thriving just 2,000 years ago; the ancient Egyptians, 3,000 years ago. Humans find it hard to think that far ahead.

Roughly every twelve to eighteen months, a nuclear plant has to shut down and all the fuel rods have to be replaced. These fuel rods are highly radioactive, so they cannot simply be taken to the nearest landfill. Strict precautions have to be taken to make sure that the spent rods do not pose a risk to the environment or to the public. Further, when a nuclear plant is "decommissioned," or shut down, the radioactive components in the core have to be disposed of properly. All of this is a difficult technical undertaking and one that carries a high expense.

Several proposals have been made for ways to dispose of high-level nuclear waste. One proposal is to launch it into space. Others are to bury it on a remote island or in the polar ice sheets. So far, these have not been attempted. Another proposal is to bury the waste under the seabeds. While technically possible, the expense of doing so would be enormous.

The most widely accepted possibility is to bury nuclear waste underground in stable geological formations. The waste would undergo first a process called vitrification (from the Latin word vitrium, meaning "glass"). This means that the waste is mixed with silica (like sand) and melted into glass beads. This process makes the waste more stable and reduces the chance that radiation could seep out into the air or water. The beads are then buried in an area that is geologically stable (that is, it does not experience earthquakes, tremors, or volcanic activity). When the storage facility is full, it would be sealed with rock.

The problem with this method is that no community wants to be home to the storage site. Nuclear waste would have to be trucked in, with the potential for accidents. Then the nuclear waste would be stored nearby, essentially forever. In 1983 President Ronald Reagan signed into law the Nuclear Waste Disposal Act. Under the act, the federal government took on responsibility for nuclear waste disposal. The act required the U.S. Department of Energy to find a suitable site for underground storage, then build the facility. In 2002 the department identified Yucca Mountain in Nevada as the most suitable site. Understandably, Nevadans do not want to be the dumping ground for the nation's nuclear industry and have opposed this plan. The state's governor notified the federal government that Nevada opposed the plan. The U.S. Congress voted to override the governor's objections. Accordingly, the federal government has designated the Yucca Mountain site as a long-term storage facility for about 70,000 metric tons of nuclear waste. As of late 2005, however, the issue was still not entirely resolved. No steps had been taken to construct the facility.

Another problem the nuclear industry has created is "mill tailings." These are waste materials created in mining uranium ore. The materials contain trace amounts of uranium left behind, as well as radium and thorium, both radioactive. The radioactive material cannot simply be left in place. The federal government, specifically the U.S. Nuclear Regulatory Commission, regulates the removal, storage, and monitoring of mill tailings.

Terrorism

After the terrorist attacks on the United States on September 11, 2001, policy makers raised concerns about the security of the nation's nuclear power plants. It is known that members of al-Qaeda, the Islamic terrorist network, have been instructed and trained in ways to attack power plants. The concerns of policy makers and nuclear regulatory officials are many:

As they did on September 11, terrorists could hijack an airliner and fly it into a nuclear power plant. The scientific director of the Nuclear Control Institute believes that a direct, high-speed impact by a large airliner "would in fact have a high likelihood of penetrating a containment building" with a nuclear reactor inside. "Following such an assault," he said, "the possibility of an unmitigated [unstopped] loss-of-coolant accident and significant release of radiation into the environment is a very real one." Other scientists believe that most nuclear plants could withstand the impact of an airliner.

Why Yucca Mountain?

The federal government identified Yucca Mountain, about 100 miles (161 kilometers) northwest of Las Vegas, as the best site in the United States for long-term nuclear waste disposal. This site was selected for a number of reasons that highlight the problems of disposing of nuclear waste:

The area has a dry climate. Yucca Mountain receives only about 7.5 inches (19 centimeters) of rainfall each year. Most of the rain runs off or evaporates. The rainfall that remains moves through the rock at a rate of only about .5 inch (1.27 centimeters) per year.

Yucca Mountain is stable geologically. Studies have shown that Yucca Mountain has not changed much for at least one million years. The earth surrounding the mountain does not shift because of volcanoes or earthquakes. Because the waste would be 1,000 feet (305 meters) below the surface, any earthquakes that did take place would likely not allow any of the material to leak out. This is because earthquakes are most intense at the Earth's surface.

The Yucca Mountain site has a deep water table. The water table, the level at which underground water is reached, is about 2,000 feet (610 meters) below the surface. The nuclear waste would be stored about 1,000 feet (305 meters) below the surface. Therefore, the water would never reach the waste. If by some chance it ever did, the water that flows under Yucca Mountain continues to flow underground into Death Valley, a forbidding desert. None of this water is used to supply water to nearby cities. Further, the Yucca Mountain site is in an enclosed water basin. This means that the area is completely surrounded by higher land. This in turn means that water flows downward and stays put. It does not spill into aquifers (water-bearing rock and sand) that supply drinking water.

The area is in a remote location. No one lives on Yucca Mountain, and the nearest people are 15 miles (24 kilometers) away. Most of the land around Yucca Mountain, about 1,375 square miles (3,561 square kilometers), has been taken over by the federal government. It is also on the edge of sites that were once used to test nuclear weapons, sites on which no one wants to live or work. If that area is added in, the unpopulated area is 5,470 square miles (14,167 kilometers).

Finally, access to the Yucca Mountain site is highly restricted. The U.S. Air Force maintains training sites and gunnery ranges in the area. The area is dense with security personnel and procedures, so it would be nearly impossible for anyone to disturb the site. Further, geologists have determined that the site has no valuable minerals, oil, precious metals, or other assets. Therefore, geologists believe that, even thousands of years from now, no one would have any reason to dig the site up.

Terrorists could steal plutonium or highly enriched uranium, either from the plants themselves of from uranium enrichment facilities. It takes only about 18 pounds (8 kilograms) of plutonium or 55 pounds (25 kilograms) of highly enriched uranium to build a nuclear weapon. But in the nuclear industry, these materials are moved about by the ton, and accurate records are not always kept. Policy makers believe that a sophisticated terrorist group could steal these materials and make a nuclear bomb. The materials could also be used to construct so-called "dirty bombs," or what experts call "radiation dispersal devices." These are bombs made of conventional explosives such as dynamite that are packed with nuclear materials, even nuclear waste. The explosion would disperse, or distribute, the radioactive materials around a wide area. The result would be public panic and an area contaminated with radiation.

Policy makers are also concerned about security at nuclear facilities. After September 11, training exercises were carried out at nuclear plants to see how well the plants' personnel could resist a terrorist attack. Military personnel disguised as terrorists attempted to gain access to these plants. Some experts claim that at nearly one-half of U.S. nuclear power plants, armed guards were not able to stop these mock attacks.

A final concern is nuclear proliferation. Proliferation means "spreading," and the concern is that nations can develop nuclear power—or claim to—and convert their nuclear capabilities into weapons. In 2005 many nations of the world, including the United States, were opposing nuclear development programs in Communist North Korea and Iran. While these countries insisted that their programs were for peaceful purposes, worries persisted that they were trying to develop nuclear weapons.

ENVIRONMENTAL IMPACT

The chief benefit to the environment of nuclear power plants is that they do not emit (give off) harmful gases, such as carbon dioxide and sulfur dioxide. In this way they differ from conventional power plants, which emit these gases primarily because they burn coal, a fossil fuel. If the energy generated by nuclear power plants worldwide were instead generated by burning coal, the amount of additional carbon dioxide released into the atmosphere would be about 1,600 million tons. Moreover, burning coal releases toxic heavy metals, including arsenic, cadmium, lead, and mercury. Nuclear energy prevents release into the atmosphere of about 90,000 tons of these metals each year. France's heavy reliance on nuclear power has lowered that country's air pollution from electrical generation by 80 to 90 percent.

By not emitting these gases, nuclear energy does not contribute to environmental problems such as air pollution, smog, and the "greenhouse effect." The greenhouse effect refers to the ability of some gases, such as carbon dioxide, to accumulate in the air. The theory is that in doing so, they act like a greenhouse, trapping the sun's heat. In turn, many scientists believe that this trapped heat is increasing average temperatures around the world. This increase is referred to as "global warming." Global warming is blamed for the melting of the polar ice, raising sea levels and endangering coastal cities. (Not all scientists agree that this is happening.) Further, by not emitting pollutants, nuclear power plants do not contribute to acid rain. Acid rain is any form of precipitation that is more acidic than normal because the water has absorbed acidic pollutants from the air. Acid rain can harm crops and forests. It can also contribute to the deterioration of buildings and public monuments, which dissolve because of the acid in precipitation.

Nuclear power plants also do not harm surrounding bodies of water. A myth that some people believe is that nuclear plants discharge water into nearby lakes and streams that is either radioactive or extremely hot. This is not true. The water released from a nuclear plant never comes into contact with the radiation. Further, if the water is too hot to be discharged, it is cooled either in a cooling pond or in cooling towers before release.

Supporters of nuclear power point out that some other alternative forms of energy do not have the same low impact on the environment, especially hydroelectric dams. While such dams have the benefit of not emitting harmful gases or pollutants, the dams have a major impact on the surrounding environment. By turning rivers into huge lakes, they disrupt vegetation and wildlife. Many dams have displaced (driven out) large numbers of people. Further, the reservoirs behind hydroelectric dams emit their own form of pollution. As the water level of the reservoir falls, the wet ground that surrounds it supports the growth of vegetation. As the water rises, this vegetation is covered and rots. The rotting vegetation emits methane gas, a pollutant. In addition, hydroelectric dams have an adverse effect on fish because they disrupt breeding and spawning grounds.

Nuclear power plants do not have harmful effects on wildlife. In fact, they often can have beneficial effects. For example, when cooled water is released from the plant, the water often contributes to the formation of wetlands. These wetlands can become nesting grounds and provide habitat for birds, fish, and other animals. Some companies that build and run nuclear plants even develop wildlife preserves and parks in the surrounding area, where plants grow abundantly in the moist soil.

Even species that are endangered (that is, in danger of becoming extinct) have found new life around nuclear plants. Some of these species thrive nearby, including such endangered species as bald eagles, red-cockaded woodpeckers, peregrine falcons, osprey, and the beach tiger beetle. The areas around nuclear plants are also home to such nonendangered species as wild turkeys, sea lions, bluebirds, kestrels, wood ducks, and pheasant.

Again, supporters of nuclear power point out that other forms of alternative energy do not have the same benefits. They agree that solar power and wind power are cleaner forms of energy, but they require huge "farms" of solar panels or windmills to produce significant amounts of electricity. Some argue that wind farms hurt an area's bird populations because the birds become almost hypnotized by the turning blades and fly right into them, where they are killed. By reducing an area's bird populations, the rodents that birds eat can multiply freely and cause rodent infestations.

Nuclear power protects land and animal habitats. Per unit of electricity, nuclear power plants take up far less land than other types of power-generating stations. For example, assume a plant that produces 1,000 megawatts of power (a megawatt is a million watts, so a thousand megawatts is 1 billion watts). To produce the same amount of power, a solar "farm" would need 35,000 acres of solar panels. A wind farm would require 135,000 acres devoted to windmills. In contrast, a typical nuclear power plant takes up only about 500 acres of land.

Further, the fuel nuclear power plants use, uranium, is very energy dense. This means that a pound of the fuel produces far more energy than a pound of coal. For example, one metric ton of uranium, or about 2,200 pounds (998 kilograms), will power a 1,000-megawatt nuclear power plant for two weeks. This fuel would come from about nine metric tons of mined uranium oxide. The same amount of energy from coal would require about 160,000 metric tons, or almost 353 million pounds. Thus, mining nuclear fuel has much less impact on the environment.

With regard to energy output, some nuclear power opponents say that these figures are misleading. They point out that conventional fuels like coal have to be burned to process uranium for use as fuel. They are correct, but the amount of conventional energy that has to be burned to do so is about 2 percent of the amount of energy the uranium will produce.

ECONOMIC IMPACT

In examining the cost of nuclear energy, many factors have to be taken into account. Some of these are obvious, such as construction costs and the cost of mining uranium. Others are more hidden and include taxes, licensing fees, interest payments on debt, and the like. Thus, any examination of the economic costs and benefits of nuclear energy involves complex calculations.

The first cost comparison involves the fuel itself. Uranium has to be mined, converted, enriched, and loaded into fuel rods. Coal has to be mined, but it can be used as is. On the other hand, the cost of transporting nuclear fuel is low because of its energy density. The cost of transporting coal is high because large volumes have to be shipped.

Per unit of energy, the cost of a nuclear power plant is generally higher than that of a conventional power plant. Nuclear power plants have to be built to the highest standards. Many of their systems are redundant, or repetitive, for safety reasons. On the other hand, coal-fired plants have additional costs because of requirements that they have pollution-control devices, such as scrubbers that remove particles from their emissions. Debt also increases the cost of nuclear plants. Because building these plants is so expensive, power companies have to borrow large sums of money, and they have to pay interest on that debt. Thus, high interest payments have added to their costs.

Nuclear power plants have higher maintenance costs than do conventional power plants. For example, corrosion and cracking are common problems in the water pipes in boiling water reactors. These components have to be replaced at great cost. In the meantime, the reactor is shut down. It is not producing energy, but workers still have to be paid and debt still has to be financed.

Both conventional and nuclear power plants have normal day-to-day costs. Nuclear facilities require highly trained technicians, engineers, safety inspectors, health workers, and the like, increasing labor costs. Conventional plants are relatively simple to operate, so they do not require as many highly trained workers. However, they require a larger labor force because of the amount of labor involved in running the plant's operations.

Nuclear plants face other charges as well. The license fee for a nuclear reactor is almost $3 million. The license for nuclear fuel use is over $2.5 million. Many nuclear plants pay $15 to $20 million in local property taxes. In addition, the Nuclear Regulatory Commission requires nuclear plant operators to take on expenses for other specialized needs, including, for example, radiographers who measure radiation in the plant. Producing nuclear energy does not come cheap.

On top of all these expenses, the nuclear industry spends many dollars for nuclear waste disposal. Coal-fired plants have only to dispose of ash. Further, the cost of decommissioning a nuclear power plant is high, often 4 percent of the initial cost of construction. A coal-fired plant that is put out of commission essentially just has to be knocked down and carted away. Yet most costs are comparable. The end result is that nuclear power is slightly more expensive than coal.

SOCIETAL IMPACT

The societal impact of nuclear power tends to be a matter more of perceptions and public sentiment than facts. Opinions about nuclear power are likely to depend on opinions about science. On the one hand, many people place a great deal of faith in science. They believe that science can solve many of the world's ills. Science, for example, can increase crop yields in poorer nations. It can reduce and eventually eliminate many diseases. And it can provide for the energy needs of the six billion people who live on Earth—a number that is likely to grow significantly as the twenty-first century progresses. Scientists, with their specialized knowledge, have become almost like magicians who solve the world's problems.

As the sheer volume of scientific information grows each year, however, the public feels disconnected from scientists and their magic. Few people know how a toaster works, let alone something as complex as a nuclear power plant. Further, they believe that while science can solve problems, it has also caused problems. In their view, the Earth and its resources have been exploited in the name of science. The atmosphere and bodies of water have been polluted because of scientific and technological advancement. Some of the people who feel this way yearn for a simpler time, when people (in their view) lived in harmony with the natural world. They were attuned to the cycles of the natural world and accepted them rather than trying to conquer them through science.

Nuclear energy stands at the center of this dilemma. Supporters of nuclear energy point to its clear benefits. It provides large amounts of power. It does not release pollution into the atmosphere. It does not consume resources whose supply will eventually run out. It does not make countries such as the United States dependent on foreign sources of fuel. It has an exemplary safety record, and improvements in the design of nuclear power plants make them safer than ever. Perhaps most importantly, nuclear power is the best hope for developing nations such as India and China. These and other countries are attempting to find a place for their large populations among the developed nations of the world. To do so, they need energy.

This point of view is not shared by all people. Many environmentalists believe that nuclear power plants are a disaster waiting to happen. Their views are sometimes supported by the mass media, which tends to focus on bad news rather than good. A documentary prepared by the Public Broadcasting Service (PBS) is a case in point. The documentary was titled "Meltdown at Three Mile Island." This title is dramatic, but it is false. No "meltdown" occurred at Three Mile Island.

BARRIERS TO IMPLEMENTATION OR ACCEPTANCE

The popular culture adds to the climate of distrust and emotional debate surrounding nuclear energy. Movies routinely depict scientists as "mad," as people bent on making scientific discoveries no matter what effects those discoveries might have on the human community. Cable-television science fiction channels routinely run movies about creatures that have been mutated into killer beasts because of science, especially nuclear science. At best, the stereotype of the scientist is one of an unappealing, slightly eccentric person. In this climate, the mysteries of nuclear power become an easy target for people's fears and uncertainties about the future.

During the first years of the twenty-first century, nuclear energy development was very much on hold, particularly in Western nations such as those in North America and Europe, as well as Australia. Public sentiment in the West favors other alternatives, such as solar, wind, and hydrogen. Less developed nations, though, do not have the luxury of picking and choosing, and many are going ahead with plans for nuclear power plants.

For More Information

Books

Angelo, Joseph A. Nuclear Technology. Westport, CT: Greenwood Press, 2004.

Domenici, Peter V. A Brighter Tomorrow: Fulfilling the Promise of Nuclear Energy. Lanham, MD: Rowman and Littlefield, 2004.

Heaberlin, Scott W. A Case for Nuclear-Generated Electricity: (Or Why I Think Nuclear Power Is Cool and Why It Is Important That You Think So Too). Columbus, OH: Battelle Press, 2003.

Kaku, Michio, and Jennifer Trainer, eds. Nuclear Power: Both Sides. New York: Norton, 1983.

Lusted, Marcia, and Greg Lusted. A Nuclear Power Plant. San Diego, CA: Lucent Books, 2004.

Morris, Robert C. The Environmental Case for Nuclear Power. St. Paul, MN: Paragon House, 2000.

Seaborg, Glenn T. Peaceful Uses of Nuclear Energy. Honolulu, HI: University Press of the Pacific, 2005.

Web sites

"The Discovery of Fission." Center for History of Physics. http://www.aip.org/history/mod/fission/fission1/01.html (accessed on December 17, 2005).

"Nuclear Terrorism—How to Prevent It." Nuclear Control Institute. http://www.nci.org/nuketerror.htm (accessed on December 17, 2005).

"Safety of Nuclear Power." Uranium Information Centre, Ltd. http://www.uic.com.au/nip14.htm (accessed on December 17, 2005).

"What Is Uranium? How Does It Work?" World Nuclear Association. http://www.world-nuclear.org/education/uran.htm (accessed on December 17, 2005).

Nuclear Energy

In the early 1970s many Americans favored the use of nuclear power to generate electricity. Reactors had been in operation since 1956, providing what appeared to be cleaner, more efficient energy than power plants that burned fossil fuels. In addition, the nation had plenty of uranium, the fuel used in U.S. reactors, so nuclear plants could help reduce U.S. dependence on foreign energy sources.

However, by the beginning of the twenty-first century opinion had turned: Voices were being raised in the United States—as well as around the world—in opposition to building additional nuclear power plants. In fact, some people wanted existing plants shut down. Two incidents—an accident in 1979 at the Three Mile Island nuclear power plant in Pennsylvania, in which the reactor core lost coolant and partially melted, and the 1986 catastrophe at Chernobyl in the Soviet Union, in which a reactor exploded and released huge amounts of radioactivity into the atmosphere—greatly increased concerns about the safety of nuclear power. Reports of design flaws, cracks, and leaks in other reactors fueled public fears. Furthermore, the safe disposal of radioactive waste, which is a by-product of nuclear energy, had become a scientific and political headache.

Supporters of nuclear power say it is as safe as any other form of energy production, as long as it is monitored properly. They point to the growing problems related to the use of fossil fuels: global warming, acid rain, and the damage caused by mining and transporting fossil fuels. This concern over fossil fuels has led some environmentalists who had previously opposed nuclear power to reconsider their position. Nonetheless, environmental, safety, and economic concerns have restrained growth in the nuclear industry since the mid-1970s. Figure 5.1 shows that from 1988 through 2007 nuclear energy’s share of electricity production leveled off at about 19%.

How Nuclear Energy Works

In a nuclear power plant, fuel (uranium in the United States) in the core of the reactor generates a nuclear reaction (fission) that produces heat. In a pressurized water reactor, the heat from the reaction is carried away by water under high pressure, which heats a second water stream, producing steam. (See Figure 5.2.) The steam runs through a turbine, making the attached generator spin, which produces electricity. The large cooling towers associated with nuclear plants cool the steam after it has run through the turbines. A boiling water reactor works much the same way, except that the water surrounding the core boils and directly produces the steam, which is then piped to the turbine generator.

The challenges faced by those who operate a nuclear power reactor include finding fuel (uranium 235) that will sustain a chain reaction, maintaining the reaction at a level that yields heat but does not escalate out of control and explode, and coping with the radiation produced by the chain reaction.

Radioactivity

Radioactivity is the spontaneous emission of energy and/or high-energy particles from the nucleus of an atom. One type of radioactivity is produced naturally and is emitted by radioactive isotopes (or radioisotopes), such as radioactive carbon (carbon 14, or C-14) and radioactive hydrogen (H-3, or tritium). The energy and high-energy particles that radioactive isotopes emit include alpha rays, beta rays, and gamma rays.

Isotopes are atoms of an element that have the usual number of protons but different numbers of neutrons in their nuclei. For example, twelve protons and twelve neutrons make up the nucleus of the element carbon. One isotope of carbon, C-14, has twelve protons and fourteen neutrons in its nucleus.

Radioisotopes (such as C-14) are unstable isotopes, and their nuclei decay (break apart) at a steady rate. Decaying radioisotopes produce other isotopes as they emit energy and/or high-energy particles. If the newly formed nuclei are radioactive as well, they emit radiation and change into other nuclei. The final products in this chain are stable, nonradioactive nuclei.

Radiation and radioisotopes reach our bodies daily, emitted from sources in outer space and from rocks and soil on earth. Figure 5.3 shows that radon is the largest source of radiation to which humans are exposed. This gas is formed in rocks and soil from the radioactive decay of radium. Most prevalent in the northern half of the United States, radon can enter cracks in basement walls and remain trapped there. Prolonged exposure to high levels of radioactive radon is thought to lead to lung cancer. Other radioisotopes, in minute quantities, are used in medicine as diagnostic tools.

Radiation was discovered at the beginning of the twentieth century by Antoine Henri Becquerel (1852–1908), Marie Curie (1867–1934), and Pierre Curie (1859–1906). Decades later, other scientists determined that they could unleash energy by artificially breaking apart atomic nuclei. Such a process is called nuclear fission. Scientists discovered that they could produce the most energy by bombarding the nuclei of an isotope of uranium called uranium 235 (U-235). The fission of a U-235 atom releases several neutrons, which have the potential to penetrate other U-235 atomic nuclei and cause them to fission. In this way the fission of a single U-235 atom begins a cascading chain of nuclear reactions. (See Figure 5.4.) If this series of reactions is regulated to occur slowly, as it is in nuclear power plants, the energy emitted can be captured for a variety of uses, such as generating electricity. If this series of reactions is allowed to occur all at once, as in an atomic bomb, the energy emitted is explosive. (Plutonium 239 can also be used to generate a chain reaction similar to that of U-235.)

Mining Nuclear Fuel

In the United States, U-235 is used as nuclear fuel. Most of it is found in the form of ore in Wyoming and New Mexico, where it is mined using methods similar to those for other metal ores. The one difference is that uranium mining can expose workers to radioactivity. Uranium atoms split by themselves at a slow rate, causing radioactive substances such as radon to accumulate slowly in the deposits.

After it is mined, uranium must be concentrated, because uranium ore generally contains only 0.1% uranium metal by weight. To concentrate the uranium, it goes through a process called milling: the ore is first crushed, and then various chemicals are poured slowly through the crushed ore to dissolve the uranium. When the uranium—called yellowcake because of its color—is extracted from this chemical solution, it is 85% pure by weight. However, this uranium is 99.3% nonfissionable U-238 and only 0.7% fissionable U-235. Other processes are necessary to create enriched uranium, which has a higher percentage of fissionable uranium.

To enrich uranium, yellowcake is first converted into uranium hexafluoride (UF₆). Cylinders of this gas are sent to a gaseous diffusion plant, where the uranium is heated in a furnace (UF₆ vaporization). (See Figure 5.5.) The enriched uranium is then converted into oxide powder (UO₂), which is made into fingertip-sized fuel pellets. The pellets are less than 0.5 inches (1.3 cm) in diameter, but each one can produce as much energy as 120 gallons (454 L) of oil. The pellets are stacked in rods, which are tubes about 12 feet (3.7 m) long. Many rods (see “Control rods” in Figure 5.2) are bundled together in assemblies, and hundreds of these assemblies make up the core of a nuclear reactor.

Domestic Nuclear Energy Production

The percentage of U.S. electricity supplied by nuclear power grew considerably during the 1970s and early to mid-1980s and then leveled off. (See Figure 5.1.) According to the Energy Information Administration (EIA), in Annual Energy Review 2007 (June 2008, http://www.eia.doe.gov/aer/pdf/aer.pdf), nuclear power supplied only 5% of the total electricity generated in the United States in 1973. In 2007 nuclear electricity net generation reached 806.5 billion kilowatt-hours (kWh), or 19% of the nation’s electricity. Thirty-one states had 104 nuclear reactors in operation in 2005. Figure 5.6 shows that most of these reactors were located east of the Mississippi River.

No new nuclear power plants have been ordered since 1978, and some have closed. (See Table 5.1.) The number of operable nuclear generating units peaked in 1990 with 112 units; as of 2007, 104 units were operating. (See Figure 5.7.) The decline in nuclear power plants stems from several related issues. Financing is difficult to find, and construction has become more expensive, partly because of longer delays for licensing, but also because of regulations instituted following the Three Mile Island accident in 1979. Still, output of electricity at existing plants has increased, achieved largely through an increase

in average capacity factor. The capacity factor is the proportion of electricity produced to what could have been produced at full-power operation. The EIA reveals that in 2007 the average capacity factor for U.S. nuclear power plants was 92%, an all-time high. Better training for operators, longer operating cycles between refueling, and control-system improvements contributed to increased plant performance.

Outlook for Domestic Nuclear Energy

In Annual Energy Outlook 2008 (2008, http://www.eia.doe.gov/oiaf/aeo/pdf/0383(2008).pdf), the EIA predicts that the capacity of nuclear power plants will increase from 100.2 gigawatts in 2006 to 114.9 gigawatts in 2030. About 17 gigawatts of capacity will come from new plants and 2.7 gigawatts from power uprates (an increase in the power output of a nuclear power plant accomplished by adding a more highly enriched uranium fuel to the existing fuel). The plant must be able to operate safely at the higher power level. These increases will be partially offset by 4.5 gigawatts of retirements. A power uprate is accomplished by adding a more highly enriched uranium fuel to the existing fuel. The plant must be able to operate safely at the higher power level.

Electricity generation from nuclear power plants is predicted to grow from 787 billion kWh in 2006 to 917 billion kWh in 2030. The share that nuclear power contributes to electricity generation in the United States is expected to decrease slightly from 19% in 2007 to 18% in 2030.

International Production

At 2.6 trillion kWh, nuclear power provided about 15% of the total 17.3 trillion kWh of electricity produced in the world during 2005. (See Table 5.2.) The U.S. Nuclear Regulatory Commission (NRC) indicates in 2007–2008 Information Digest (2007, http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1350/v19/sr1350v19.pdf) that as of December 31, 2006, electricity was being produced by 439 nuclear plants worldwide. Fifty-two other plants were under construction or on order.

In 2005 the United States led the world in nuclear power electricity generation with 782 billion kWh, followed by France (429 billion kWh) and Japan (278.4 billion kWh). (See Table 5.2.) Together, the three countries generated 57% of the world’s nuclear electric power. About 80% of France’s electrical power was produced by nuclear energy in 2005, followed by Belgium (56%), Sweden (45%), and Switzerland (38%). Japan produced 27% of its electricity by nuclear power generation in 2005, and the United States, 19%. Canada produced 14% of its electricity with nuclear power; the primary source for electricity generation in Canada is hydroelectric power.

Worldwide, the EIA projects in International Energy Outlook 2008 (June 2008, http://www.eia.doe.gov/oiaf/ieo/) that nuclear generating capacity will increase slightly from 374 gigawatts in 2005 to 498 gigawatts in 2030. Some countries whose capacities are projected to increase are:

• Canada, from 13 gigawatts in 2005 to 18 gigawatts in 2030
• Japan, from 47 gigawatts in 2005 to 58 gigawatts by 2030
• China, from 7 gigawatts in 2005 to 52 gigawatts by 2030
• India, from 3 gigawatts in 2005 to 20 gigawatts by 2030
• United States, from 100 gigawatts in 2005 to 116 gigawatts in 2025, and then drop to 115 gigawatts by 2030

Aging Nuclear Power Plants

At some point, the nuclear plants now operating worldwide may need to be retired. Most of them were designed to last about thirty years. Some plants showed serious levels of deterioration after as few as fifteen years; some have lasted well beyond their thirty-year expectations.

There are three methods of retiring, or decommissioning, a reactor. Safe enclosure, or mothballing, involves removing the fuel from the plant, monitoring any radioactive contamination (which is usually very low or nonexistent), and guarding the structure to prevent anyone from entering until eventual dismantling and decontamination activities occur. Entombment, which was used at Chernobyl, involves permanently encasing the structure in a long-lived material such as concrete. This procedure allows the radioactive material to remain safely on-site. Immediate dismantling involves decontaminating and tearing down the facility within a few months or years. This method is initially more expensive than the other options but removes the long-term costs of

monitoring both the structure and the radiation levels. It also frees the site for other uses, including the construction of another nuclear power plant. Nuclear power companies are also seeking alternative uses for nuclear shells, including the conversion of old nuclear plants to gas-fired plants.

Paying for the closing, decontamination, or dismantling of nuclear plants has become an issue of intense public debate. The industry contends that the cost of decommissioning retired plants and handling radioactive wastes will continue to escalate, causing serious financial problems for electric utilities.

A New Generation of Nuclear Plants

In 2001 the Generation IV International Forum (July 14, 2005, http://gif.inel.gov/roadmap/), a group of nuclear nations, agreed to work together to create a new generation of nuclear reactors. Their intent was to develop new systems by 2030 that “present significant improvements in economics, safety and reliability and sustainability over currently operating reactor technologies.” As of September 2008, its members included Argentina, Brazil, Canada, the European Atomic Energy Community, France, Japan, the Republic of Korea, the Republic of South Africa, Switzerland, the United Kingdom, and the United States.

The group chose six nuclear power technologies for development:

• Gas-cooled fast reactor —this technology would provide a closed system, helium-cooled reactor that minimizes long-lived radioactive waste by recycling it.
• Very-high-temperature reactor (VHTR) — with core outlet temperatures reaching 1,832° Fahrenheit (1,000° C),

  TABLE 5.2 World net electric power generation by type, 1980, 1990, and 2005 [CONTINUED]
  SOURCE: “Table 11.16. World Net Generation of Electricity by Type, 1980, 1990, and 2005 (Billion Kilowatthours),” in Annual Energy Review 2007, U.S. Department of Energy, Energy Information Administration, Office of Energy Markets and End Use, June 2008, http://www.eia.doe.gov/aer/pdf/aer.pdf (accessed June 28, 2008)
  [Billion kilowatthours]
  	Fossil fuels			Nuclear electric power			Hydroelectric powera			Totalb
  Region and country	1980	1990	2005P	1980	1990	2005P	1980	1990	2005P	1980	1990	2005P
  Asia and Oceaniac	907.7	1,626.8	4,270.2	92.7	279.9	524.3	262.7	404.1	735.3	1,268.0	2,333.0	5,589.1
  Australia	74.5	131.8	218.4	.0	.0	.0	12.8	14.0	15.5	87.7	146.4	236.7
  China	227.9	465.2	1,922.1	.0	.0	50.3	57.6	125.1	397.0	285.5	590.3	2,371.8
  India	69.7	198.9	539.2	3.0	5.6	15.7	46.5	70.9	99.0	119.3	275.5	661.6
  Indonesia	10.6	35.3	103.4	.0	.0	.0	2.2	6.7	10.7	12.8	43.0	120.3
  Japan	381.6	524.0	645.5	78.6	192.2	278.4	87.8	88.4	77.4	549.1	817.3	1,024.6
  South Korea	29.8	45.5	222.7	3.3	50.2	139.4	1.5	4.6	3.6	34.6	100.4	366.2
  Taiwan	31.3	43.6	164.5	7.8	31.6	38.0	2.9	8.2	7.8	42.0	83.3	210.3
  Thailand	12.3	38.7	115.7	.0	.0	.0	1.3	4.9	5.7	13.6	43.7	124.6
  Other	70.1	143.8	338.6	(s)	.4	2.4	50.0	81.2	118.5	123.5	233.2	472.9
  World	5,588.5	7,137.9	11,455.3	684.4	1,908.8	2,625.6	1,722.9	2,145.4	2,893.5	8,026.9	R11,319.2	17,344.0
  aExcludes pumped storage, except for the United States. bWood, waste, geothermal, solar, wind, batteries, chemicals, hydrogen, pitch, purchased steam, sulfur, and miscellaneous technologies are included in total. cExcludes countries that were part of the former U.S.S.R. dIncludes only countries that were part of the former U.S.S.R. P = Preliminary. — = Not applicable. (s) = Less than 0.05 billion kilowatthours. Note: Totals may not equal sum of components due to independent rounding. web page: For related information, see http://www.eia.doe.gov/international.

  the VHTR would be used to produce hydrogen and to meet specific high-temperature heating needs of the petrochemical industry and others.
• Supercritical-water-cooled reactor (SCWR) —the SCWR is a high-temperature, high-pressure water-cooled reactor that increases efficiency by operating above the thermodynamic critical point of water. Water under high pressure does not boil and turn to steam; the thermodynamic critical point of water refers to the temperature and pressure at which the liquid state ceases to exist and the liquid and gaseous forms become indistinguishable. For water, this point is 705° Fahrenheit (374 ° C).
• Sodium-cooled fast reactor (SFR) —intended for electricity generation, this system uses a sodium-cooled reactor and a closed fuel cycle to increase safety and reduce high-level radioactive waste.
• Lead-cooled fast reactor (LFR) —designed with small electricity grids and developing countries in mind, the LFR proposes a factory-built system that would need refueling only every fifteen to twenty years. It features a fast-spectrum lead or liquid metal-cooled reactor and a closed cycle for reducing waste.
• Molten salt reactor —in this system, the fuel is a liquid mixture of sodium, zirconium, and uranium fluorides, which eliminates the need for fuel production. By-products can be recycled back into the fuel mixture.

Each of the new technologies builds on the knowledge gained during the three other periods of nuclear reactor development: Generation I—the experimental reactors developed in the 1950s and 1960s; Generation II—large, central-station nuclear power reactors, such as the 104 plants still operating in the United States, built in the 1970s and 1980s; and Generation III—the advanced light-water reactors built in the 1990s, primarily in East Asia, to meet that region’s expanding electricity needs.

Nuclear Safety

Safety has been an issue from the beginning of the industry. For example, some plant sites, especially those near earthquake fault lines, have raised serious questions for governments, industry leaders, and environmentalists. Plants can be shut down for a variety of reasons. For example, in 1987 the NRC shut down the Peach Bottom nuclear plant in Delta, Pennsylvania, because control room operators were found sleeping on duty. The plant was not restarted until 1989, after reactor operators had been retrained and changes in management had occurred. In addition, many workers resigned, retired, or were demoted—a few were even fired. The plant, as well as some of the workers, was fined by the NRC. In February 2005 the Kewaunee Power Station in Carlton, Wisconsin, was shut down after it was discovered that emergency shutdown systems could be compromised by flooding from water storage tanks located in an adjacent part of the plant. Even though no flood actually occurred, operations at the plant were halted until the shutdown systems could be protected from a potential water threat. In November 2007 the Perry Nuclear Power Plant near Cleveland, Ohio, automatically shut down when the system that supplies coolant water to the reactor malfunctioned. Nuclear plants shut down from time to time, but most safety questions have been focused by major accidents since the late 1970s.

Three Mile Island

On March 28, 1979, the Three Mile Island nuclear facility near Harrisburg, Pennsylvania, was the site of the worst nuclear accident in U.S. history. Information released several years after the accident revealed that Unit 2, one of the reactors operating at the site, came much closer to meltdown than either the NRC or the industry had previously indicated. Temperatures inside the reactor, which were first said to have reached 3,500° Fahrenheit (1,927° C), are now known to have reached at least 4,800° Fahrenheit (2,649° C). The temperature needed to melt uranium dioxide fuel is 5,080° Fahrenheit (2,804° C). When meltdown occurs, an uncontrolled explosion may result, unlike the controlled nuclear reaction of normal operation.

The emergency system at Three Mile Island was designed to dump water on the hot core of the reactor and spray water into the reactor building to stop the production of steam. During the accident, however, the valves leading to the emergency water pumps closed. Another valve was stuck in the open position, drawing water away from the core, which then became partially uncovered and began to melt.

The accident resulted in no deaths or injuries to plant workers or the nearby community. On average, area residents were exposed to less radiation than that of a chest X-ray. Nevertheless, the incident raised concerns about nuclear safety, which resulted in more rigorous safety standards in the nuclear power industry and at the NRC. Antinuclear sentiment was fueled as well, heightening Americans’ wariness of nuclear power as an energy source.

The nuclear reactor in Unit 2 at Three Mile Island has been in monitored storage since it underwent cleanup. Operation of the reactor in Unit 1 resumed in 1985.

Chernobyl

On April 26, 1986, the most serious nuclear accident ever occurred at Chernobyl, a nuclear plant in what is now Ukraine (then part of the Soviet Union). At least thirty-one people died and hundreds were injured when one of the four reactors exploded during a badly run test. Millions of people were exposed to some levels of radiation when radioactive particles were released into the atmosphere. About 350,000 people were eventually evacuated from the area, including residents of what are now the neighboring nations of Belarus and the Russian Federation, who were endangered by fallout carried by the prevailing winds.

The cleanup was a huge project. Helicopters dropped tons of limestone, sand, clay, lead, and boron on the smoldering reactor to stop the radiation leakage and reduce the heat. Workers built a giant steel and cement sarcophagus to entomb the remains of the reactor and contain the radioactive waste.

The International Atomic Energy Agency (IAEA) indicates in Chernobyl’s Legacy: Health, Environmental, and Socioeconomic Impacts (April 2006, http://www.iaea.org/Publications/Booklets/Chernobyl/chernobyl.pdf) that about one thousand people involved in the initial cleanup, including emergency workers and the military, received high doses of radiation. Eventually, over six hundred thousand people would be involved in decontamination and containment activities. The long-term effects of whatever exposure they received are being monitored. According to the IAEA, the most measurable effect of the radiation has been the incidence of thyroid cancer in children. At least four thousand children—which is considered a very large number, given the size of the population—have been treated for the cancer.

Even though some of the evacuated land has been declared fit for habitation again, several areas that received heavy concentrations of radiation are expected to be closed for decades. The three remaining nuclear reactors at Chernobyl continue to operate. The site itself is off-limits to all but official personnel.

An International Agreement on Safety

In September 1994 forty nations, including the United States, signed the International Convention on Nuclear Safety, an agreement that requires them to shut down nuclear power plants if necessary safety measures cannot be guaranteed. In “Summary Report of the 4th Review Meeting of the Contracting Parties to the Convention on Nuclear Safety” (June 2008, http://www-ns.iaea.org/downloads/ni/safety_convention/summary-report-april2008-final.pdf), the IAEA states that as of April 14, 2008, sixty countries and one regional organization had ratified the agreement. The agreement applies to land-based civil nuclear power plants and seeks to avert accidents such as the 1986 explosion at Chernobyl. Ukraine, which inherited the Chernobyl plant after the collapse of the Soviet Union, signed the agreement. Signers must submit reports on atomic installations and, if necessary, make improvements to upgrade safety at the sites. Neighboring countries may call for an urgent study if they are concerned about a reactor’s safety and the potential fallout that could affect their own population or crops.

Radioactive Waste

Working in a laboratory in Chicago, Illinois, in 1942, the physicist Enrico Fermi (1901–1954) assembled enough uranium to cause a nuclear fission reaction. His discovery transformed both warfare and energy production. The experiment also produced a small packet of radioactive waste material that may remain dangerous for one hundred thousand years. That first radioactive waste lies buried under a foot of concrete and two feet of dirt on a hillside in Illinois.

Radioactive waste is produced at all stages of the nuclear fuel cycle, from the initial mining of the uranium to the final disposal of the spent fuel from the reactor. The term radioactive waste encompasses a broad range of material with widely varying characteristics. Some is barely radioactive and safe to handle, whereas other types are intensely hot and highly radioactive. Some waste decays to safe levels of radioactivity in a matter of days or weeks, whereas other types will remain dangerous for thousands of years. The U.S. Department of Energy and the NRC have defined the major types of radioactive waste.

Uranium Mill Tailings

Uranium mill tailings are sandlike wastes produced in uranium refining operations. Even though they emit low levels of radiation, their large volume (10 million to 15 million short tons [9.1 million to 13.6 million t] annually) poses a hazard, particularly from radon emissions and groundwater contamination. The dangers of uranium mill tailings were not realized until the early 1970s, so many miners and residents of the western United States were exposed to them. Cancer incidences are high among miners who worked before the 1970s. In addition, the World Information Source on Energy Uranium Project reports in “Health Impacts for Uranium Mine and Mill Residents— Science Issues” (April 9, 2008, http://www.wise-uranium.org/uhr.html) that those residing near uranium mills have shown increased risks of leukemia, lung and renal cancer, and birth defects.

Low-Level Waste

Low-level waste, which contains lesser levels of radioactivity, includes trash (such as wiping rags, swabs, and syringes), contaminated clothing (such as shoe covers and protective gloves), and hardware (such as luminous dials, filters, and tools). This waste comes from nuclear reactors, industrial users, government users (but not nuclear weapons sites), research universities, and medical facilities. In general, low-level waste decays relatively quickly (in ten to one hundred years).

High-Level Waste

Spent nuclear fuel (used reactor fuel) is high-level radioactive waste. Uranium fuel can be used for twelve to eighteen months, after which it is no longer as efficient in splitting its atoms and producing the heat needed to generate electricity. It must be removed from the reactor and replaced with fresh fuel. Some of the spent fuel is reprocessed to recover the usable uranium and plutonium, but the radioactive material that remains is dangerous for thousands of years.

Transuranic Wastes

Transuranic wastes are eleven man-made radioactive elements with atomic numbers greater than that of uranium (ninety-two) and therefore beyond (trans-) uranium (-uranic) on the Periodic Table of the elements. Their half-lives (the time it takes for half the radioisotopes present in a sample to decay to nonradioactive elements) are thousands of years. They are found in trash produced mainly by nuclear weapons plants and are therefore part of the nuclear waste problem but not directly the concern of nuclear power utilities.

Mixed Waste

Mixed waste is high-level, low-level, or transuranic waste that also contains hazardous nonradioactive waste. Such waste poses serious institutional problems, because the radioactive portion is regulated by the Department of Energy or the NRC under the Atomic Energy Act of 1954, whereas the U.S. Environmental Protection Agency (EPA) regulates the nonradioactive elements under the Resource Conservation and Recovery Act of 1976.

Radioactive Waste Disposal

Disposing of radioactive waste is unquestionably one of the major problems associated with the development of nuclear power; radioactive waste is also a by-product of nuclear weapons plants, hospitals, and scientific research. Even though federal policy is based on the assumption that radioactive waste can be disposed of safely, new storage and disposal facilities for all types of radioactive waste have frequently been delayed or blocked by concerns about safety, health, and the environment.

The highly toxic wastes must be isolated from the environment until the radioactivity decays to a safe level. In the case of plutonium, for example, the half-life is twenty-six thousand years. At that rate, it will take at least one hundred thousand years before radioactive plutonium is no longer dangerous. Any facilities built to store such materials must last at least that long.

Regulation of Radioactive Waste Disposal

As of January 2006 the NRC had entered into agreements with thirty-three states to regulate the management, storage, and disposal of certain nuclear waste within their borders.

Disposal of Uranium Mill Tailings

Mill tailings are usually deposited in large piles next to the mill that processed the ore. In 1978 Congress passed the Uranium Mill Tailing Radiation Control Act, which requires mill owners to follow EPA standards for the cleanup of uranium and thorium after milling operations have permanently closed. The companies must cover the mill tailings to control the release of radon gas for one thousand years.

Disposal of Low-Level Waste

According to the NRC, in 2007–2008 Information Digest, as of June 2007 three low-level licensed nuclear waste facilities were operating in the United States: in Barnwell, South Carolina; in Hanford, Washington; and in Clive, Utah, where Energy Solutions accepts large amounts of mill tailings and low-level waste, such as contaminated soil or debris from demolished buildings. Four low-level radioactive waste facilities have been closed: in West Valley, New York (closed 1975); in Maxey Flats, Kentucky (closed 1977); in Sheffield, Illinois (closed 1978); and in Beatty, Nevada (closed 1993).

The design of a low-level waste facility is shown in Figure 5.8. Wastes are buried in shallow underground

sites in specially designed canisters. Underground storage may or may not include protection by concrete vaults.

The Low-Level Radioactive Waste Policy Amendments Act of 1985 encouraged states to enter into compacts, which are legal agreements among states for low-level radioactive waste disposal. Table 5.3 shows these compacts. Even though each compact is responsible for the development of disposal capacity for the low-level waste generated within the compact, new disposal sites have yet to be built. As Table 5.3 shows, two of the three operational low-level sites are located in the Northwest Compact and one is in the Atlantic Compact. Nuclear power facilities located in compacts without low-level waste disposal sites must petition the compact to export their low-level radioactive waste to one of the three operating disposal sites.

Disposal of High-Level Waste

A major step toward shifting the responsibility for disposal of high-level radioactive wastes (spent fuel) from the nuclear power industry to the federal government was taken in 1982, when Congress passed the Nuclear Waste Policy Act. It established national policy, set a detailed timetable for the disposal and management of high-level nuclear waste, and authorized construction of the first high-level nuclear waste repository. A 1987 amendment to the Nuclear Waste Policy Act directed investigation of Yucca Mountain, about 100 miles (161 km) northwest of Las Vegas, Nevada, as a potential site.

The project was highly controversial, however, and Congress did not approve the Yucca Mountain site until July 2002. The state of Nevada challenged the decision, but in 2004 federal courts dismissed the challenge. In April 2006 the U.S. secretary of energy announced proposals to facilitate licensing and construction of the repository, which was expected to take about five years. In June 2008 the Department of Energy submitted a waste repository license application to the NRC—more than a decade after the repository was originally scheduled to open. Thus, by mid-2008, no long-term, permanent disposal repository for high-level waste existed, and construction of the Yucca Mountain Repository had not yet begun.

While waiting for the development of the Yucca Mountain site, as of September 2008 spent fuel was being stored at facilities away from the power plants that generated the waste, such as at the General Electric Company facility in Morris, Illinois. Alternately, spent fuel was being stored at the nuclear power plants that generated the waste. The map in Figure 5.9 notes the sites storing spent nuclear fuel and high-level radioactive waste as of June 2008.

Figure 5.10 shows the plan for the proposed Yucca Mountain high-level nuclear waste repository. Aboveground structures for handling and packaging nuclear waste would cover approximately 400 acres (162 hectares) and be surrounded by a 3-mile (4.8-km) buffer zone. Underground, about 1,400 acres (567 hectares) would be mined, with tunnels leading to areas where sealed metal containers would be placed. This type of deep geologic disposal is widely considered by governments, scientists, and engineers to be the best option for isolating highly radioactive waste.

The repository would be designed to contain radioactive material by using layers of man-made and natural barriers. Regulations require that a repository isolate waste until the radiation decays to a level that is about the same as that from a natural underground uranium deposit. This decay time was originally estimated to be about ten thousand years, but the National Academy of Sciences has more recently recommended a higher standard of about three hundred thousand years.

After the repository has been filled to capacity, regulations require the Department of Energy to keep the facility open and to monitor it for at least fifty years from the fill date. Eventually, the repository shafts would be filled with rock and earth and sealed. At ground level, facilities would be removed and, as much as possible, the site returned to its original condition.

Scientists expect some of the man-made barriers in a repository to break down over thousands of years. Once that happens, natural barriers will be counted on to stop or slow the movement of radiation particles. The most likely way for particles to reach humans and the environment would be through water, which is why the low water tables at Yucca Mountain are so crucial. In addition, Yucca Mountain contains minerals called zeolites that will stick to the particles and slow their movement throughout the environment.

The long delay in providing disposal sites for spent nuclear fuel has been expensive for the industry. Several aging power plants are being maintained at a cost of $20 million per reactor per year simply because there is no place to send the waste once the plants are decommissioned. As of 2002, 47,023.4 metric tons (51,834.4 short tons) of nuclear uranium waste were sitting in spent fuel pools at the 104 operating and 28 permanently closed nuclear power plants. (See Table 5.4 and Table 5.1.)

Disposal of Transuranic Waste

The Waste Isolation Pilot Plant (WIPP) is the first disposal facility licensed to dispose of transuranic waste. It does not accept waste from commercial sources or electrical power plants, but disposes only of defense-related transuranic waste. It opened in March 1999 in southeastern New Mexico. Its disposal rooms were mined 2,150 feet (655 m) underground in a salt formation that is 2,000 feet (610 m) thick and that has been stable for over 200 million years. Beginning with one or two shipments per week, operations grew over the years, expanding to an all-time high of thirty-three shipments received during a single week in February 2006. In September 2006 the plant received its five-thousandth shipment of transuranic waste and announced that thirteen sites around the country, most notably the Rocky Flats Environmental Technology site in Colorado, had been completely cleaned up by that time. As of August 25, 2008, WIPP (http://www.wipp.energy.gov/shipments.htm) had received 6,851 shipments from eight sites.

Disposal of Mixed Waste

Several commercial facilities in the United States accept mixed waste. However, only the Energy Solutions facility in Clive, Utah, is permitted to accept solid mixed waste. It stores the waste in aboveground, capped embankments designed to last at least one thousand years. The storage facility is located in an isolated area 20 miles (32 km) from the nearest water supply and more than 40 miles (64 km) from the nearest populated area. Containment efforts are supported by area soil and weather conditions, as well, with little permeability (the capacity of rock or soil to transmit water) in the clay soil and fewer than 6 inches (15 cm) of rain per year.

Sites in Florida, Tennessee, and Texas offer storage for liquid or sludge materials or use thermal or chemical processes to neutralize them. Among them, Diversified Scientific Services in Kingston, Tennessee, generates electrical power from liquid mixed waste through an industrial boiler system, and the Texas-based NSSI provides drum storage.

chapter 5
NUCLEAR ENERGY

Nuclear energy is used in the United States to generate electricity and to power some navy ships. In the decades since the first commercial nuclear reactor went into operation in 1956, the nuclear power industry has had a difficult time persuading the American public of the safety of its enterprise. In the early 1970s most Americans favored the use of nuclear power because it appeared to provide cleaner, more efficient, energy than fossil fuels, and it could help reduce U.S. dependence on foreign energy sources. But by the early 2000s many people in the United States—and, indeed, around the world—opposed building additional nuclear power plants. The 1979 disaster at Three Mile Island in Pennsylvania and the 1986 catastrophe at Chernobyl in the former Soviet Union greatly increased public concerns about the safety of nuclear power, as have reports of design flaws, cracks, and leaks in other reactors. Furthermore, the safe disposal of radioactive waste, which is a by-product of nuclear energy, has proven difficult.

Supporters of nuclear power believe that it is as safe as any other form of energy production if monitored correctly. They point to growing concerns about fossil fuel use, including global warming and acid rain, as well as damage caused by mining and transporting fossil fuels. In fact, this growing concern over fossil fuels has led a small number of environmentalists who had previously opposed nuclear power to reconsider their position. Nonetheless, environmental, safety, and economic concerns have restrained growth in the nuclear industry since the mid-1970s. Unwillingness to commission new nuclear plants is evident in Figure 5.1, which shows a general leveling off of nuclear energy's share of electricity production from 1988 through 2003 at about 20%.

HOW NUCLEAR ENERGY WORKS

In a nuclear power plant, fuel (uranium in the United States) in the reactor generates a nuclear reaction (fission) that produces heat. In a pressurized water reactor (see Figure

FIGURE 5.1

5.2), the heat from the reaction is carried away by water under high pressure, which heats a second water stream, producing steam. The steam runs through a turbine (similar to a jet engine), making it and the attached electrical generator spin, which produces electricity. The steam is then cooled and recirculated. The large cooling towers associated with nuclear plants are used to cool the steam after it has run through the turbines. A boiling water reactor works much the same way, except that the water surrounding the core boils and directly produces the steam, which is then piped to the turbine generator.

FIGURE 5.2

The key problems in operating a nuclear power reactor include finding material (uranium 235) that will sustain a chain reaction, maintaining the reaction at a level that yields heat but does not escalate out of control and explode, and coping with the radiation produced by the chain reaction.

Radioactivity

Radioactivity is the spontaneous emission of energy and/or high-energy particles from the nucleus of an atom. One type of radioactivity is produced naturally and is emitted by radioactive isotopes (or radioisotopes), such as radioactive carbon (carbon 14) and radioactive hydrogen (H-3, or tritium). The energy and high-energy particles that radioactive isotopes emit include alpha rays, beta rays, and gamma rays.

Isotopes are atoms of an element that have the usual number of protons but different numbers of neutrons in their nuclei. For example, twelve protons and twelve neutrons comprise the nucleus of the element carbon. One isotope of carbon, C-14, has twelve protons and fourteen neutrons in its nucleus.

Radioisotopes (such as C-14) are unstable isotopes and their nuclei decay, or break apart, at a steady rate. Decaying radioisotopes produce other isotopes as they emit energy and/or high-energy particles. If the newly formed nuclei are radioactive as well, they emit radiation and change into other nuclei. The final products in this chain are stable, nonradioactive nuclei.

Radioisotopes reach our bodies daily, emitted from sources in outer space, and from rocks and soil on earth. Radioisotopes are also used in medicine and provide useful diagnostic tools. Figure 5.3 shows the sources of radiation.

FIGURE 5.3

As shown in Figure 5.3, radon is the largest source of radiation to which humans are exposed. This gas is formed in rocks and soil from the radioactive decay of radium. Most prevalent in the northern half of the United States, radon can enter cracks in basement walls and remain trapped there. Prolonged exposure to high levels of radioactive radon is thought to lead to lung cancer.

Decades after the discovery of radiation at the turn of the century by Antoine Henri Becquerel, Marie Curie, and Pierre Curie, other scientists determined that they could unleash energy by "artificially" breaking apart atomic nuclei. Such a process is called nuclear fission. Scientists learned that they could produce the most energy by bombarding the nuclei of an isotope of uranium called uranium 235 (U-235). The fission of U-235 releases several neutrons, which can then penetrate other U-235 nuclei. In this way the fission of a single U-235 atom could begin a cascading chain of nuclear reactions, as shown in Figure 5.4. If this series of reactions is regulated to occur slowly, as it is in nuclear power plants, the energy emitted can be captured for a variety of uses, such as generating electricity. If this series of reactions is allowed to occur all at once, as in a nuclear (atomic) bomb, the energy emitted is explosive. (Plutonium 239 can also be used to generate a chain reaction similar to that of U-235.)

Mining Nuclear Fuel

In the United States U-235, found in the form of ore, is used as nuclear fuel. The majority of uranium in the United States is found in two states: Wyoming and New Mexico. Ore that contains uranium is first located by geological methods such as drilling. Uranium-bearing ores are mined by methods similar to those used for other metal ores. However, uranium mining has the unique danger

FIGURE 5.4

of exposure to radioactivity. Uranium atoms split by themselves at a slow rate, causing radioactive substances such as radon to accumulate slowly in the deposits.

After it is mined, uranium must be concentrated, because uranium ore generally contains only 0.1% uranium metal by weight. To concentrate the uranium, it goes through a process called milling. The nuclear fuel cycle, which is shown in Figure 5.5, begins with the milling of uranium ore. In milling the ore is first crushed, and then various chemicals are poured slowly through the crushed ore to dis-solve out the uranium. The uranium is then precipitated from this chemical solution. The resulting material, called yellowcake because of its color, is 85% pure uranium by weight. But this uranium is 99.3% nonfissionable U-238 and only 0.7% fissionable U-235. Other processes result in enriched uranium, which is uranium that has a higher percentage of fissionable uranium than does yellowcake.

To produce enriched uranium, yellowcake is converted into uranium hexafluoride gas (UF6). This gas is loaded into cylinders, which are sent to a gaseous diffusion plant, shown in Figure 5.5, where uranium is made into reactor fuel (enriched). The enriched uranium is converted into oxide powder (UO2), which is made into fingertip-sized fuel pellets. The small pellets are less than one-half inch in diameter, but each one can produce as much energy as 120 gallons of oil. The pellets are stacked in tubes about twelve feet long, called rods. Many rods are bundled together in assemblies, and hundreds of these assemblies make up the core of a nuclear reactor.

DOMESTIC NUCLEAR ENERGY PRODUCTION

The percentage of U.S. electricity supplied by nuclear power grew considerably during the 1970s and 1980s before leveling off in the 1990s. In 1973 nuclear power supplied only 4.5% of the total electricity generated in the United States. By 2003 nuclear power's 19.8% share of electricity production was down only slightly from the 2001 all-time high of 20.6%. In 2002 nuclear power plant operations provided an all-time high of nuclear electricity net generation of 780.1 billion kilowatt-hours.

The increase in production of electricity in nuclear power plants was achieved largely through an increase in average capacity factor. The capacity factor is the proportion of electricity produced to what could have been produced at full-power operation. In 2002 the capacity factor was at an all-time high of 90.3%. In 2003 the capacity factor was 88.2%. Better training for operators, longer operating cycles between refueling, and control-system improvements contributed to increased plant performance.

In 2003 and 2004, 104 nuclear reactors were in operation (see Figure 5.6 and Figure 5.7) in thirty-one states. In 2003 these 104 reactors had a total net generation of 763.7 billion kilowatt-hours of energy. Most of these reactors

FIGURE 5.5

are located east of the Mississippi River, where the demand for electricity is high. The number of plants operating is lower than the 135 reactors that were either planned, in construction, or in operation in 1974.

Since 1978 no new nuclear power plants have been ordered, and many have closed. (See Table 5.1.) Several factors have contributed to the slowdown in U.S. nuclear reactor construction. Overall costs have increased as a result of more expensive financing, partly influenced by longer delays for licensing. Expenses have also increased because of regulations that were instituted as a result of the Three Mile Island incident. Operating costs have been higher than expected as well. Originally, it was projected that plants could run almost 90% of the time, with brief pauses for refueling, but for many years this was not the case.

OUTLOOK FOR DOMESTIC NUCLEAR ENERGY

In its Annual Energy Outlook 2004 (2004), the Energy Information Administration (EIA) predicted that the capacity of nuclear power plants will be maintained as they age through 2025. Thus, electricity generation by these plants is projected to increase slightly from 2002 to 2025, but its contribution to U.S. electricity production will decline as electricity generation by coal, natural gas, and renewables increases.

No nuclear units are projected to be retired between 2002 and 2025, nor are any new nuclear units expected to become operable during that time span because natural gas and coal-fired plants are projected to be more economical. However, the Nuclear Regulatory Commission (NRC) approved eighteen applications for power uprates for plants in 2002 and another nine were approved or pending as of 2003. (A power uprate is an increase in the power output of a nuclear power plant, which is accomplished by adding a more highly enriched uranium fuel to

FIGURE 5.6

the current fuel. The plant must be able to operate safely at the higher power level.)

INTERNATIONAL PRODUCTION

According to the Annual Energy Review 2003, in 2002 nuclear power provided about 17% of the world's electricity and 6.6% of total energy. Although the United States is the largest producer of nuclear power, it trails

FIGURE 5.7

other Western countries in the proportion of national electrical production generated by nuclear power. That is primarily because oil, natural gas, and coal have been more accessible in the United States than in other countries.

In 2002 the United States led the world in nuclear power generation with 780.1 billion kilowatt-hours, followed by France's 414.9 billion and Japan's 295.1 billion. (See Table 5.2.) These three countries together generated 58% of the world's nuclear electric power. France had by far the highest proportion (approximately 78%) of its electrical power produced by nuclear energy, followed by Belgium (59%), Sweden (46%), and Switzerland (41%). Japan produces 28% of its electricity by nuclear power generation, and the United States only 20%.

In its Information Digest 2004–2005, the Nuclear Regulatory Commission reported that as of December 31, 2003, there were 438 nuclear power plants in operation worldwide and fifty-four were under construction, on order, or had their construction halted, including eight in India, eight in South Korea, six in Russia, five in the Ukraine, five in Japan, and four in Romania.

Worldwide, the EIA projected in its International Energy Outlook 2004 that nuclear generating capacity will increase slightly overall, from 353 gigawatts in 2001 to 385 gigawatts in 2025. The increase will peak in 2015 with a generating capacity of 407 gigawatts. Totals for individual countries will increase for some and decrease for others. Some countries whose capacities are projected to increase from 2001 to 2025 are:

• Canada, from ten gigawatts in 2001, increasing to fifteen gigawatts in 2020, and decreasing to twelve gigawatts in 2025

TABLE 5.1

TABLE 5.2

• Japan, from forty-three gigawatts to fifty-seven gigawatts in 2020, and down to fifty-four gigawatts in 2025
• China, from two gigawatts in 2001 to twenty-one gigawatts in 2025
• India, from three to nine gigawatts
• United States, from ninety-eight to 103 gigawatts
• France, from sixty-three to seventy gigawatts

Some countries whose capacities are projected to decrease from 2001 to 2025 are:

• Germany, from twenty-one to zero gigawatts
• The United Kingdom, from twelve to four gigawatts

Some countries are planning to cut capacity radically or phase out nuclear power altogether. Sweden has legislated a nuclear phase-out by 2010 (although it is not clear that this is an attainable goal, since nearly half of Sweden's electricity comes from nuclear power). The Netherlands and Germany have strong conservation policies and well-organized antinuclear movements. The Netherlands is projected to phase out nuclear power by 2020 and Germany by 2025.

International Agreement on Safety

In September 1994 forty nations, including the United States, signed the International Convention on Nuclear Safety, an agreement that requires them to shut down nuclear power plants if necessary safety measures cannot be guaranteed. The agreement applies to land-based civil nuclear power plants and seeks to avert accidents like the 1986 explosion at Chernobyl in the former Soviet Union, the world's worst nuclear disaster to date. Ukraine, which inherited the Chernobyl plant after the collapse of the Soviet Union, signed the agreement. Signers must submit reports on atomic installations and, if necessary, make improvements to upgrade safety at the sites. Neighboring countries may call for an urgent study if they are concerned about a reactor's safety and the potential fallout that could affect their own population or crops.

POWER PLANT AGING

Like other types of power plants, nuclear power plants have a lifespan after which they must be retired because the cost of running them becomes too high. The generation of nuclear power plants currently operating was designed to last about thirty years. Some plants showed serious levels of deterioration after as few as fifteen years. However, some have lasted well beyond thirty-year expectations. Whenever a power plant—whether coal, natural gas, or nuclear—is retired, it must be demolished and cleaned up so that the site can be used again.

Decommissioning Nuclear Power Plants

Eventually, the more than 400 nuclear plants now operating worldwide will need to be retired. There are three methods of retiring, or decommissioning, a reactor: safe enclosure (mothballing), entombment, and immediate dismantling.

Safe enclosure involves removing the fuel from the plant, monitoring any radioactive contamination (which is usually very low or nonexistent), and guarding the structure to prevent anyone from entering until eventual dismantling and decontamination activities occur. Entombment, which was used at Chernobyl, involves permanently encasing the structure in a long-lived material such as concrete. This procedure allows the radioactive material to remain safely on-site but at one location. Immediate dismantling involves decontaminating and tearing down the facility within a few months or years. This process is initially more expensive than the other options but removes the long-term costs of monitoring both the structure and the radiation levels. It also frees the site for other uses, including even the construction of another nuclear power plant. Nuclear power officials are also seeking alternative uses for nuclear shells, including the conversion of old nuclear plants to gas-fired plants.

Paying for the closing, decontamination, or dismantling of nuclear plants has become an issue of intense public debate. The early closing of several plants owing to safety concerns and poor economic performance has raised the question of how the costs of decommissioning can be covered. Industry reports contend that the cost of decommissioning retired plants and handling radioactive wastes will continue to escalate, causing serious financial problems for electric utilities. In addition to coal plants, new technologies, such as wind turbines and geothermal energy, are less expensive than nuclear energy plants when all factors are considered.

A NEW GENERATION OF NUCLEAR PLANTS?

In January 2000 the United States entered into a collaboration with international partners on nuclear energy. Formally chartered in 2001, the Generation IV International Forum (GIF) is a group of leading nuclear nations that agree that nuclear energy is important to future world energy security and economic prosperity. These countries are dedicated to joint development of the "next generation" of nuclear energy systems. Members of GIF are the United States, Argentina, Brazil, Canada, France, Japan, the Republic of Korea, South Africa, Switzerland, and the United Kingdom.

The GIF countries have selected six nuclear power technologies to develop for the future. These "Generation IV" nuclear energy systems would follow the three other periods of nuclear reactor development: (a) Generation I experimental reactors developed in the 1950s and 1960s; (b) Generation II large, central-station nuclear power reactors, such as the 104 plants still operating in the United States, built in the 1970s and 1980s; and (c) Generation III advanced light-water reactors built in the 1990s, primarily in East Asia, to meet that region's expanding electricity needs.

In 2003 GIF examined more than one hundred reactor concepts and identified nineteen as potentially viable. One new concept, the advanced high-temperature reactor (AHTR), may reduce electricity production costs and may be able to produce hydrogen. GIF research and development began in 2004.

NUCLEAR SAFETY PROBLEMS

Problems have plagued the nuclear industry almost from the beginning. Some plant-site selections have been considered questionable, especially those near earthquake fault lines. Several major accidents have occurred worldwide since the late 1970s.

In the United States

three mile island. On March 28, 1979, the Three Mile Island nuclear facility near Harrisburg, Pennsylvania, was the site of the worst nuclear accident in American history. Information released several years after the accident revealed that the plant came much closer to meltdown than either the NRC or the industry had previously indicated. Temperatures inside the reactor were first said to have been 3,500 degrees Fahrenheit but are now known to have reached at least 4,800 degrees. The temperature needed to melt uranium dioxide fuel is 5,080 degrees Fahrenheit. When meltdown occurs, an uncontrolled explosion may result, unlike the controlled nuclear reaction of normal operation.

The emergency core cooling system at Three Mile Island was designed to dump water on the hot core and spray water into the reactor building to stop the production of steam. During the accident, however, the valves leading to the emergency water pumps closed. Another valve was stuck in the open position, drawing water away from the core, which then became partially uncovered and began to melt. The emergency core cooling system then began drawing water out of the basement supply and reusing it, contaminating the reactor pump, although limiting the radiation contamination to the interior of the building.

Although safety systems at the Three Mile Island facility performed well and the radiation leak was relatively small, the Three Mile incident was sensationalized in the media. Antinuclear proponents urged residents to evacuate, adding to stress levels and panic. In the end this nuclear accident resulted in no deaths or injuries to plant workers or members of the nearby community. On average, area residents were exposed to less radiation than that of a chest X-ray. Nevertheless, the Three Mile Island incident raised concerns about nuclear safety, which resulted in safety enhancements in the nuclear power industry and at the NRC. Antinuclear sentiment was fueled as well, heightening Americans' criticism of nuclear power as an energy source.

The nuclear reactor in Unit 2 at Three Mile Island has been in monitored storage since it underwent cleanup. Operation of the reactor in Unit 1 resumed in 1985.

peach bottom. In 1987 the NRC shut down the Peach Bottom nuclear plant in Delta, Pennsylvania, because control-room operators were found sleeping on duty. This was the first plant shut-down solely because of operator violations and misconduct.

In the Former Soviet Union

chernobyl. On April 26, 1986, the most serious nuclear accident ever occurred at Chernobyl, a four-reactor nuclear plant complex located in the former Soviet Union (now Ukraine) near Kiev. At least thirty-one people died and hundreds were injured when one of the four reactors exploded during a badly-run test of the reactor. Everyone in the vicinity was exposed to radiation, and radioactive particles were released into the atmosphere. About 500 people were hospitalized, and medical experts estimate that 6,000 to 24,000 cancer-related deaths have occurred over the intervening years as a result of the released radiation.

The cleanup was one of the biggest projects of its kind ever undertaken. Helicopters dropped 5,000 tons of limestone, sand, clay, lead, and boron on the smoldering reactor to stop the radiation leakage and reduce the heat. Workers built a giant steel and cement sarcophagus (stone coffin) to enshrine the remains of the reactor and contain the radioactive waste. Approximately 135,000 people were evacuated from a 300-square-mile area around the power station. Topsoil had to be removed in a nineteen-mile area and buried as nuclear waste. Buildings were washed down and the newly contaminated water and soil were carted away and buried. Agricultural products from areas nearby were declared unmarketable throughout Europe. Many of the 600,000 people involved in the immediate cleanup have suffered long-term effects of radiation exposure.

Some people at Chernobyl received 400 rems of radiation immediately following the explosion. (A rem is a standard measure of the whole-body dose of radiation. Under normal conditions, a person receives about one-tenth of a rem annually.) With a dose of twenty-five rems, a person's blood begins to change. The DNA is damaged, preventing the bone marrow from producing red and white blood cells. Sickness starts at 100 rems and severe sickness at 200 rems. Death of half the population occurs at 400 rems, and death within a week can be expected for anyone exposed to 600 rems. One estimate is that 17.5 million people, including 2.5 million children under seven years old, have had some significant exposure to radiation from Chernobyl.

In 1995 the United Nations reported that the prevalence of illnesses of all kinds was 30% above normal in the Ukraine; incidences of depression, alcoholism, and divorce were on the rise. Although the Chernobyl reactor is in the Ukraine, the neighboring nation of Belarus (with a population of 10 million people) suffered more human and ecological damage from fallout because of the prevailing winds. Thyroid cancers were 285 times pre-Chernobyl levels in Belarus in 1995, especially among children. Belarus's cabinet minister claimed at that time that a quarter of his country's national income was being spent on alleviating the effects of the disaster. As many as 375,000 people in Belarus, Ukraine, and Russia were displaced because of the accident. Contaminated forests spread radioactivity through fires, and seepage from the reactor has polluted waterways as far away as the Black Sea, some 350 miles away.

In April 1996 a fire in the woods near the Chernobyl reactor once more alarmed observers, who feared further danger to the entombed reactor and the release of radioactivity from soils and vegetation in the area. In addition, the sarcophagus built to contain the damaged reactor is reported to be crumbling. However, the Ukraine, which suffers from 40% unemployment and other enormous economic woes, claims it needs the power from the remaining reactor and that completely shutting down Chernobyl would cost too much.

Some high-technology companies have developed robots to clean up hazardous sites such as Chernobyl. Such efforts would, however, produce yet another problem: what to do with the radioactive waste once the Chernobyl sarcophagus is entered and cleaned up.

TYPES OF RADIOACTIVE WASTE

Working in a laboratory in Chicago, Illinois, in 1942, Italian physicist Enrico Fermi assembled enough uranium to cause a nuclear fission reaction. His discovery transformed both warfare and energy production, but the experiment also produced a small packet of radioactive waste materials that will remain dangerous for hundreds of thousands of years. That "first" radioactive waste lies buried under a foot of concrete and two feet of dirt on a hillside in Illinois.

Radioactive waste material is produced at all stages of the nuclear fuel cycle, from the initial mining of the uranium to the final disposal of the spent fuel from the reactor. (See Figure 5.5.) "Radioactive waste" is a term that encompasses a broad range of material with widely varying characteristics. Some is barely radioactive and safe to handle, while other types are intensely hot in terms of both temperature and radioactivity. Some waste decays to safe levels of radioactivity in a matter of days or weeks, while other types will remain dangerous for thousands of years. The U.S. Department of Energy (DOE) and the NRC define the major types of radioactive waste.

Uranium Mill Tailings

Uranium mill tailings are sand-like wastes produced in uranium refining operations. Although they emit low levels of radiation, their large volumes (10–15 million tons annually) pose a hazard, particularly from radon emissions and groundwater contamination. Since it was not until the early 1970s that the dangers of uranium mill tailings were realized, many miners and residents in the western United States had unsafe exposure to them. Cancer incidences are high among miners who worked prior to the 1970s.

Low-level Waste

Low-level waste, which contains varying lesser levels of radioactivity, includes trash (such as wiping rags, swabs, and syringes), contaminated clothing (such as shoe covers and protective gloves), and hardware (such as luminous dials, filters, and tools). This waste comes from nuclear reactors, industrial users, government users (but not nuclear weapons sites), research universities, and medical facilities. In general, low-level waste decays relatively quickly (in ten to one hundred years).

High-level Waste

Spent nuclear fuel (used reactor fuel) is high-level radioactive waste. Uranium fuel can be used for twelve to eighteen months, and then it is no longer as efficient in splitting its atoms and producing heat, which ultimately is used to generate electricity. Therefore, it must be removed from the reactor and replaced with fresh fuel. Some of the spent fuel is reprocessed to recover the usable uranium and plutonium, but the radioactive material that remains is dangerous for thousands of years.

Transuranic (TRU) Wastes

Transuranic (TRU) wastes are eleven human-made radioactive elements with atomic numbers greater than that of uranium (ninety-two) and therefore beyond ("trans-") uranium ("-uranic") on the periodic chart of the elements. Their half-lives—the time it takes for half the radioisotopes present in a sample to decay to nonradioactive elements—are thousands of years. They are found in trash produced mainly by nuclear weapons plants and are therefore part of the nuclear waste problem but not directly the concern of nuclear power utilities.

Mixed Waste

Mixed waste is high-level, low-level, or TRU waste that also contains hazardous nonradioactive waste. Such waste poses serious institutional problems, because the radioactive portion is regulated by the DOE or NRC under the Atomic Energy Act (AEA; PL 83–703), while the Environmental Protection Agency regulates the nonradioactive elements under the Resource Conservation and Recovery Act (RCRA; PL 95–510).

RADIOACTIVE WASTE DISPOSAL

Disposing of radioactive waste is unquestionably one of the major problems associated with the development of nuclear power; radioactive waste is also a by-product of nuclear weapons plants, hospitals, and scientific research. Although federal policy is based on the assumption that radioactive waste can be disposed of safely, new storage and disposal facilities for all types of radioactive waste have frequently been delayed or blocked by concerns about safety, health, and the environment.

The highly toxic wastes must be isolated from the environment until the radioactivity decays to a safe level. In the case of plutonium, for example, the half-life is 26,000 years. At that rate, it will take at least 100,000 years before radioactive plutonium is no longer dangerous. Any facilities built to store such materials must last at least that long.

Regulation of Radioactive Waste Disposal

The Nuclear Regulatory Commission, other federal agencies, and the states regulate radioactive materials. As of 2004, the NRC had entered into agreements regarding radioactive waste with 33 states, which are called Agreement States. These states, under their agreements with the NRC, regulate the management, storage, and disposal of certain nuclear waste within their states.

Disposal of Uranium Mill Tailings

Mill tailings are usually deposited in large piles next to the mill that processed the ore. In 1978 Congress passed the Uranium Mill Tailing Radiation Control Act (PL95–604). This law requires mill owners to follow Environmental Protection Agency (EPA) standards for cleanup of uranium and thorium after milling operations have permanently closed. They must cover the mill tailings to control the release of radon gas; the cover must effectively control radon releases for 1,000 years. Figure 5.8 shows the locations of uranium mill tailings disposal sites. The sites are located in the western United States because deposits of uranium ore are more plentiful there.

Disposal of Low-level Waste

Low-level waste is classified according to its potential hazards. Commercial sites that dispose of these wastes must be licensed by either the NRC or Agreement States. In 2004 three low-level waste facilities were operational in the United States. These facilities accept a broad range of low-level radioactive waste and are located in Barnwell, South Carolina, and Richland, Washington. In addition, Envirocare of Utah accepts large amounts of mill tailings and low-level waste, such as contaminated soil or debris from demolished buildings and from facilities that have shut down. Four low-level radioactive waste facilities have been closed: West Valley, New York (closed 1975); More-head/Maxey

FIGURE 5.8

Flats, Kentucky (closed 1977); Sheffield, Illinois (closed 1978); and Beatty, Nevada (closed 1993).

The design of a low-level waste facility is shown in Figure 5.9. Wastes are buried in shallow underground sites in the specially designed canisters in which they are shipped as shown in the diagram. Underground storage may or may not include protection by concrete vaults.

The Low-level Radioactive Waste Policy Amendments Act of 1985 (PL 99–240) encouraged states to enter into compacts, which are legal agreements among states for low-level radioactive waste disposal. Figure 5.10 shows these compacts. Although each compact is responsible for the development of disposal capacity for the low-level waste generated within the compact, new disposal sites have yet to be built. As Figure 5.10 shows, two of the three operational low-level sites are located in the Northwest Compact and one is in the Southeast Compact. Facilities located in compacts with no current low-level waste disposal sites must petition the compact to export their low-level radioactive waste to one of the three operating disposal sites.

Disposal of High-level Waste

A major step toward shifting the responsibility for disposal of high-level radioactive wastes (spent fuel) from the nuclear power industry to the federal government was taken in 1982, when Congress passed the Nuclear Waste Policy Act (PL 97–425). It provided the first comprehensive national policy and detailed timetable for the management

FIGURE 5.9

and disposal of high-level nuclear waste and authorized construction of the first high-level nuclear waste repository. A 1987 amendment to the Nuclear Waste Policy Act directed investigation of Yucca Mountain in Nevada as a potential site. In 2004 no long-term, high-level permanent waste disposal repository for spent fuel existed. While

FIGURE 5.10

waiting for the development of the Yucca Mountain site, spent fuel was being stored at away-from-reactor storage facilities, such as the General Electric Company facility in Morris, Illinois, or at the nuclear power plants that generated the waste. (See Figure 5.7 for the locations of operating nuclear reactors in the United States.)

On July 9, 2002, the U.S. Senate joined the U.S. House of Representatives in approving the Yucca Mountain site. The State of Nevada, however, challenged the constitutionality of this resolution. Nevertheless, in 2004, federal courts dismissed all challenges to the site selection of Yucca Mountain but did call into question the legality of the 10,000-year standard for the facility set by the Environmental Protection Agency because the EPA did not accept the National Academy of Sciences recommendation of a higher standard of perhaps 300,000 years. While the agency works on a new standard, Congress could decide to allow the old one to stay in place. Congress approved $2 million for the state's work on the project and $8 million for local governments for fiscal year 2005, an increase from the state's $1 million and local government's $4 million received for fiscal year 2004. The DOE must still submit its license application for the proposed Yucca Mountain nuclear repository. It will take about five years to construct the facility, which is already more than a decade behind schedule.

Figure 5.11 shows the location of the proposed radioactive waste disposal facility at Yucca Mountain. The proposed repository would look like a large mining complex. It would have facilities on the surface for handling and packaging nuclear waste and a large mine about 1,000 feet underground. Here, plans call for the waste to be placed in sealed metal canisters arranged vertically in the floor of underground tunnels. Above-ground facilities would cover approximately 400 acres and be surrounded by a three-mile buffer zone. Underground, about 1,400 acres would be mined, consisting of tunnels leading to the areas where waste containers would be placed and service areas near the shafts and ramps that provide access from the surface. This type of "deep geologic" disposal is widely considered by governments, scientists, and engineers to be the best option for isolating highly radioactive waste.

The repository would be designed to contain radioactive material by using layers of human-made and natural barriers. Regulations require that a repository isolate waste until the radiation decays to a level that is about the same as that from a natural underground uranium deposit. This decay time was originally estimated at be about 10,000 years, but the National Academy of Sciences has more recently recommended a higher standard of about 300,000 years.

After the repository has been filled to capacity, regulations require the DOE to keep the facility open and to monitor it for at least fifty years from the fill date. This will allow experts to monitor conditions inside the repository and retrieve spent fuel if necessary. Eventually, the repository shafts will be filled with rock and earth and sealed. At the ground level, facilities will be removed, and, as much as possible, the DOE will take steps to return the site to its original condition.

Scientists assume that over thousands of years, some of the human-made barriers in a repository will break down. Once that happens, natural barriers will be counted on to stop or slow the movement of radiation particles. The most

FIGURE 5.11

TABLE 5.3

likely way for particles to reach humans and the environment would be through water, which is why the low water tables at Yucca Mountain are so crucial. Yucca Mountain also has certain chemical properties that act as another barrier to the movement of radioactive particles. Minerals in the rock called zeolites would stick to the particles and slow their movement throughout the environment.

The long delay in providing disposal sites for spent nuclear fuel, coupled with the accelerated pace at which nuclear plants are being retired, has created a crisis in the industry. Several aging plants are being maintained at a cost of $20 million a year for each reactor simply because there is no place to send the waste once the plants are decommissioned. Table 5.3 shows that as of 2002 more than 47,000 metric tons of nuclear uranium waste were sitting in spent fuel pools at the 104 operating and nineteen permanently closed nuclear power plants. When a nuclear plant shuts down, the nuclear waste and the radioactive equipment stay on the premises because there is no place to put them. As a result, every nuclear power plant in the United States has become a temporary nuclear waste disposal site. Plants that close must wait until a repository opens to be decommissioned or dismantled.

Disposal of Transuranic Waste

The first disposal facility licensed to dispose of transuranic waste opened on March 26, 1999. The Waste Isolation Pilot Plant (WIPP) is located in the desert in southeastern New Mexico. WIPP facilities include disposal rooms mined 2,150 feet underground in a 2,000-foot-thick salt formation that has been stable for more than 200 million years.

Disposal of Mixed Waste

As mentioned previously, mixed waste is jointly regulated by the Environmental Protection Agency, which regulates the hazardous waste component of mixed waste, and the Nuclear Regulatory Commission and the Department of Energy, which regulate the radioactive component of mixed waste. There are a variety of commercial facilities in the United States, including Envirocare (see "Disposal of Low-level Waste"), that accept mixed waste.

Nuclear Power

The nuclear power plant

Types of nuclear power plant

Safety concerns

Nuclear waste management

History

Nuclear fusion

The future of nuclear power

Resources

Nuclear power is any method of doing work that makes use of nuclear fission or nuclear fusion reactions. In its broadest sense, the term refers to both the uncontrolled release of nuclear energy, as in fission or fusion weapons, and to the controlled release of energy, as in nuclear power plants. Most commonly, however, the expression “nuclear power” is reserved for the latter. Approximately 430 nuclear reactors devoted to the manufacture of electricity are operating worldwide.

The world’s first exposure to nuclear power came with the detonation of two fission (atomic) bombs over the Japanese cities of Hiroshima and Nagasaki in 1945, events that coincided with the end of World War II. (It has long been assumed by many historians and members of the general public that these atomic bombings were necessary to produce a Japanese surrender and to forestall a United States invasion of Japan; this belief has been disputed by some historians in recent years.) A number of scientists and laypersons perceived an optimistic aspect of these terrible events; they hoped that the power of nuclear energy could be harnessed for human good. Those hopes have been realized, but to only a modest degree. Starting in the 1970s, intense political opposition to nuclear power arose in many nations, including the U.S. Some technical problems associated with the use of nuclear power have never been satisfactorily solved, although proponents of this technology argue that none are insurmountable. After three decades of progress in the development of controlled nuclear power, interest in this energy source has leveled off and, in many nations, declined. Indeed, strong popular opposition to nuclear power exists in many countries today, and nuclear power has become a locus of political struggle, with citizens’ groups (supported by some scientists) ranged, typically, against industry and government experts. Nuclear advocates see nuclear opponents as irrationally fearing nuclear technology; nuclear opponents see nuclear advocates as irresponsibly advocating use of unreliable nuclear technology. The nuclear–power issue remains a highly contentious one in many nations.

The nuclear power plant

A nuclear power plant is a system in which some of the energy released by nuclear fission is used to generate electricity. Every such plant contains four fundamental elements: reactor, coolant system, electrical–power generating unit, and safety system.

The source of energy in a nuclear reactor is a fission reaction in which neutrons collide with nuclei of uranium–235 or plutonium–239 (the fuel), causing them to split apart. The products of a fission reaction include not only energy but also new elements (known as fission products) and free neutrons. A constant and reliable flow of neutrons is insured in the reactor by a moderator, which slows down the speed of neutrons, and by control rods, which limit the number of neutrons available in the reactor and, hence, the rate at which fission can occur. In a nuclear weapon, the fission chain reaction, once triggered, proceeds at an exponentially increasing rate, resulting in an explosion; in a nuclear reactor, it proceeds at a steady, controlled rate. Most commercial nuclear power plants are incapable of undergoing an explosive nuclear chain reaction, even should their safety systems fail; this is not true of all research reactors (e.g., some breeder reactors).

Energy produced in the reactor is carried away by means of a coolant such as pressurized water, liquid sodium, or carbon dioxide gas. The circulating coolant absorbs heat in the reactor; once outside the reactor, it is allowed to boil or the heat it contains is used to boil water in a secondary loop. Steam produced in either of these ways is then piped into the electrical generating unit, where it turns the blades of a turbine. The turbine, in turn, turns a generator that produces electrical energy.

The high cost of constructing a modern nuclear power plant—three to four billion dollars, in the U.S.—reflects in part the wide range of safety features needed to protect against various possible mishaps, especially those which could release to the environment any of the plant’s inventory of radioactive substances. (Small special–purpose reactors, such as those used to power nuclear submarines or aircraft carriers, have different costs and technical features from the large, land–based reactors used to supply electrical grids.) Some of those features are incorporated into the reactor core itself. For example, all of the fuel in a reactor is sealed in a protective coating made of a zirconium alloy. The protective coating, called a cladding, helps retain heat and radioactivity within the fuel, preventing it from escaping into the plant itself.

Every nuclear plant is also required to have an elaborate safety system to protect against the most serious potential problem of all, loss of coolant. If such an accident were to occur, the reactor core might melt itself down, possibly breaching the structures which contain it and releasing radioactive materials to the rest of the plant and, perhaps, to the outside environment. To prevent such an accident, the pipes carrying the coolant to and from the reactor are required to be very thick and strong. In addition, back–up supplies of the coolant must be available to replace losses in case of a leak.

On another level, the whole plant itself (in much of the world, including Europe and the U.S.) is required to be encased within a dome–shaped containment structure made of steel–reinforced concrete several feet thick. The containment structure is designed to prevent the release of radioactive materials in case of an accident within the reactor. The containment also serves against as a barrier against efforts to deliberately damage the reactor from outside, as by firing shoulder–launched missiles at the reactor or crashing a hijacked airplane into it.

Another safety feature is a system of high–efficiency filters through which all air leaving the building must pass. These filters are designed to trap microscopic particles of radioactive materials that might otherwise be vented to the atmosphere. Other specialized devices and systems have also been developed for dealing with other kinds of accidents in various parts of the power plant.

Types of nuclear power plant

Nuclear power plants differ from each other primarily in the methods they use for transferring heat produced in the reactor to the electricity generating unit. Perhaps the simplest design of all is the boiling water reactor plant (BWR), in which coolant water surrounding the reactor is allowed to boil and form steam. This steam is then piped directly to turbines, which produce rotary mechanical power that turns electrical generators. A very different type of plant is one that was popular in Great Britain for many years; this design that carbon dioxide as a coolant. In this type of plant, carbon dioxide gas passes through the reactor core, absorbs heat produced by fission reactions, and is piped into a secondary system where it gives up some of its energy to water, which begins to boil. This steam is then used to power a turbine and generator.

Safety concerns

In spite of all the systems developed by nuclear engineers, the general public has long had serious concerns about the use of such plants as sources of electrical power. In France, for example, where more than half of the electrical power supply comes from nuclear power plants, public support for nuclear power has declined in recent years; France has now placed a moratorium on the construction of new plants. Germany, which relies on nuclear power for approximately 30% of its electricity, has decided to phase out all of its nuclear power plants as quickly as it can obtain replacement power from other sources. In the U.S., enthusiasm for nuclear power in the 1950s and 1960s faded in the 1970s, giving way to widespread—but often unscientific or ill–founded—public unease about nuclear dangers, a vigorous antitechnology and antinuclear activist movement, and investor concern over the high monetary cost of nuclear power; no new nuclear power plants have been ordered in the U.S. for over 20 years. The nuclear–power industry remains strongest in Asia, where approximately 25 new plants are now under construction.

One concern about nuclear power plants, of course, is an echo of the world’s first exposure to nuclear power, the atomic bomb blasts. Many people fear that a nuclear power plant may go out of control and explode like a nuclear weapon. In spite of experts’ insistence that such an event is impossible, a few major disasters have perpetuated the fear of nuclear power plants exploding or failing catastrophically in some other mode. Although commercial nuclear power plants cannot explode, they have a demonstrated potential to pass out of the control of their operators, with unpredictable consequences. By far the most serious of those events was the explosion that occurred at the Chernobyl nuclear power plant near Kiev in the Ukraine in 1986.

On April 16 of that year, one of the four power–generating units in the Chernobyl complex exploded, blowing the top off the containment building. (The explosion was caused by hydrogen gas released by the overheating core; it was not a nuclear explosion.) Hundreds of thousands of nearby residents were exposed to dangerous levels of radiation and were evacuated from the area. Radioactive clouds released by the explosion were detected downwind in Scandinavia and western Europe. More than a decade later, the remains of the Chernobyl reactor remain far too radioactive for anyone to spend more than a few minutes near the former reactor core. The Soviet government had, of course, always insisted that such a disaster was impossible. In the U.S., the most famous nuclear incident to date is the accident at the Three Mile Island nuclear plant in 1979. The reactor suffered a partial meltdown that was contained by the giant, pill–shaped steel vessel containing the core; some radioactive gas was released to the environment, and a hydrogen explosion raised pressures inside the containment dome to within a few pounds per square inch of the dome’s design pressure. Again, experts had reassured the public that the chances against such an event were literally astronomical—comparable to those of a giant meteor striking a major city.

Critics of nuclear power also worry about the amount of radioactivity released by nuclear power plants on a day–to–day basis. This concern is probably of less importance than is the possibility of a major disaster; studies have shown that nuclear power plants are so well shielded that the amount of radiation to which nearby residents are exposed is no more than that of a person living many miles away. Nevertheless, some epidemiological evidence hints that the small amounts of radioactive material released during routine operation may have detectable medical effects on nearby populations. These claims are, of course, intensely disputed.

In any case, safety concerns in the United States have been serious enough to essentially bring the construction of new plants to a halt in the last decade. Licensing procedures are now so complex and so expensive that few industries are interested in working their way through the bureaucratic maze to construct new plants. However, it should also be noted that orders for new nuclear power plants in the U.S. had practically ceased in the late 1970s, years before the Chernobyl or Three Mile Island accidents or the regulatory response to them. Some analysts argue that the stagnation of the nuclear–power industry should be attributed primarily to economics, rather than to political opposition.

Nuclear waste management

Perhaps the single most troubling issue for the nuclear power industry is waste management. Nuclear wastes can be classified into two general categories, low–level wastes and high-level wastes. The former consist of materials that release a relatively modest level of radiation and/or that will soon decay to a level where they no longer present a threat to humans and the environment. Storing these materials in underground or underwater reservoirs for a few years or in some other system is usually a satisfactory way of handling these materials.

High-level wastes are a different matter. After a period of time, the fuel rods in a reactor are no longer able to sustain a chain reaction and must be removed. These rods are still highly radioactive, however, and present a serious threat to human life and the environment that can be expected to last for tens of thousands of years. These rods and any materials derived from them (as, for example, during chemical dismantling of the rods to extract their plutonium for the production of nuclear weapons or for use as a nuclear fuel), are considered high-level wastes.

For more than two decades, the United States government has been attempting to develop a plan for the storage of high-level nuclear wastes. At one time, the plan was to bury the wastes in a salt mine near Lyons, Kansas. Objections from residents of the area and other concerned citizens made that plan infeasible. More recently, the government decided to construct a huge crypt in the middle of Yucca Mountain in Nevada for the burial of high-level wastes. The government insists that Yucca Mountain is safe and will eventually become the long–term storage site for the nation’s high-level radioactive wastes. Until the site is put into full operation, however (if it is), the wastes slated for burial in it are held in “temporary” storage on the grounds nuclear power plants throughout the United States.

History

The first nuclear reactor was built during World War II as part of the Manhattan Project to build an atomic bomb. This reactor was constructed under the direction of Italian physicist Enrico Fermi (1901–1954) in a large room beneath the squash courts at the University of Chicago. Until the day on December 2, 1942, when the Chicago reactor was first put into operation, scientists had relied entirely on mathematical calculations to determine the effectiveness of nuclear fission as an energy source; thus, the scientists who constructed the first reactor were taking an extraordinary chance.

That reactor consisted of alternating layers of uranium and uranium oxide with graphite (carbon) as a moderator. Cadmium control rods were used to control the concentration of neutrons in the reactor. Since the various parts of the reactor were constructed by piling materials on top of each other, the unit was at first known as an “atomic pile.”

Nuclear fusion

Many scientists believe that the ultimate solution to the world’s energy problems may be in the harnessing of nuclear fusion. A fusion reaction is one in which two small atomic nuclei combine with each other to form one larger nucleus. For example, two hydrogen nuclei may combine with each other to form the nucleus of an atom known as deuterium, or heavy hydrogen. Fusion reactions are responsible for the production of energy in stars. Most commonly, four hydrogen atoms fuse in a series of reactions to form a single helium atom. An important byproduct of these reactions is the release of an enormous amount of energy. By weight, a fusion reaction releases many times more energy than does a fission reaction.

The world was introduced to the concept of fusion reactions in the 1950s when first the United States and then the Soviet Union exploded fusion (hydrogen) bombs. The energy released in the explosion of each such bomb was more than 1,000 times greater than the energy released in the explosion of a single fission bomb such as that used by the U.S. to destroy the city of Hiroshima.

KEY TERMS

Cladding —A material that covers the fuel elements in a nuclear reactor in order to prevent the loss of heat and radioactive materials from the fuel.

Containment —Any system developed for preventing the release of radioactive materials from a nuclear power plant to the outside world.

Coolant —Any material used in a nuclear power plant to transfer the heat produced in the reactor core to another unit in which electricity is generated.

Generator —A device for converting kinetic energy (the energy of movement) into electrical energy.

Neutron —A subatomic particle that carries no electrical charge and that has a mass of zero.

Nuclear fission —A reaction in which a larger atomic nucleus breaks apart into two roughly equal, smaller nuclei.

Nuclear fusion —A reaction in which two small nuclei combine with each other to form one larger nucleus.

Nuclear pile —The name given to the earliest form of a nuclear reactor.

Turbine —A device consisting of a series of baffles mounted on a wheel around a central shaft used to convert the energy of a moving fluid into the energy of mechanical rotation.

As with fission, scientists and nonscientists alike expressed hope that fusion reactions could someday be harnessed as a source of energy for everyday needs. This line of research has been much less successful, however, than research on fission power plants. In essence, the problem has been to find a way of producing, in a controlled, sustainable fashion, the very high temperatures (millions of degrees Celsius) needed to sustain fusion. Optimistic reports of progress on a fusion power plant appear in the press from time to time, but some authorities now doubt that fusion power will ever be an economic reality.

The future of nuclear power

Proponents of nuclear power argue that a fresh round of power–plant construction should be undertaken to meet growing electricity demand. Coal–fired plants presently produce most of the world’s electricity, but release air pollution and greenhouse gases; nuclear power, its advocates argue, does not release these substances. Given the threat of global climate change, it follows that it is of utmost importance to build more nuclear power plants. Opponents of nuclear power respond that greater reductions in air pollution and greenhouse–gas emissions could be achieved by spending the same money on non-nuclear technologies (i.e., efficiency improvements and renewable energy sources such as solar power). They also argue that a massive increase in the number of nuclear power plants bring increased risks for nuclear accidents and for proliferation of nuclear weapons to states that do not as yet have them. Globally, nuclear power is approximately stagnant as of 2006; wind power is being deployed more rapidly than nuclear power, and at a fraction the cost per kilowatt–hour delivered. Whether it is about to undergo the renaissance urged by its advocates or the accelerated phaseout urged by its opponents may not be apparent for some years.

See also Accelerators; Atomic models; Bioterrorism.

Resources

BOOKS

Caldicott, Helen. Nuclear Power is Not the Answer. New York: New Press, 2006.

Ramsey, Charles B. Commercial Nuclear Power: Assuring Safety for the Future. Charleston, SC: BookSurge Publishing, 2006.

Richard, L., and Georges Charpak. Megawatts and Megatons: The Future of Nuclear Power. University of Chicago Press, 2002.

PERIODICALS

Ahearne, J.F. “Intergenerational issues regarding nuclear power and nuclear waste.” Risk Analysis 20 (2001): 763–770.

Hoffert, Martin, et al. “Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet.” Science vol. 298, no. 5595 (Nov. 1, 2002): 981–987.

David E. Newton

Larry Gilman

Nuclear Power

Introduction

Nuclear power is the generation of electricity from the breakdown of unstable atoms, especially atoms of uranium and plutonium. Nuclear power plants produce large amounts of electricity, but, in operation, no carbon dioxide. A nuclear power plant thus does not contribute to the greenhouse effect on a daily operational basis.

Nuclear electricity was first produced in useful quantities in 1954, and hundreds of plants have since been built worldwide. Nuclear power has been stagnant for several decades in some countries, such as the United State, and successful in others, notably France. In some countries, it has been politically controversial due to public concerns about its safety. There have also been international concerns about the use of materials from nuclear power plants to produce nuclear weapons, as U.S. officials and others have alleged Iran is doing as of 2007.

In the early 2000s, many governments, including those of Russia and of the United States, were advocating the construction of a new wave of nuclear power plants, citing global climate change as the reason for such construction. A few environmentalists, though not most, had recently agreed that nuclear power was necessary to reduce climate change. The proposal to revive nuclear power to mitigate greenhouse warming has many critics, however, who argue that nuclear power is expensive, slow to deploy, and inherently unsafe because of its radioactive wastes and its potential for accidents, terrorist attacks, and nuclear weapons proliferation.

Historical Background and Scientific Foundations

What Is Nuclear Power?

The structure of the atom—a small, dense nucleus surrounded by a cloud of electrons—was not understood until 1911, when British physicist Ernest Rutherford (1871-1937) and coworkers found that the subatomic particles called alpha particles, when fired at a thin film of gold, would occasionally bounce right back at their source as if they had struck a wall. This showed that most of the mass of the gold atoms must be concentrated in a small, dense core.

During the following 15 years, scientists discovered that atomic nuclei contain two types of particles, namely protons and neutrons. The proton has a positive electrical charge and the neutron has no charge. The chemical characteristics of each atom are determined by how many protons it contains, since an atom tends to attract to itself as many electrons (which are negatively charged) as will balance out the positive charges of its protons. The tendency of protons to attract electrons is the basis of chemical bonding; forming and breaking the electrical bonds between atomic nuclei and electrons stores and releases chemical energy. All energy released by burning fuels such as gasoline or hydrogen is from electrical bonds.

Another kind of energy resides in the atom in the bonds between protons and neutrons in nuclei. These bonds are much stronger than the bonds between protons and electrons, since they are created by a force (the nuclear force) that acts at shorter range and is far more powerful than the electrical force. Making and breaking nuclear bonds can consume or release energy. When nuclei come together to form a larger nucleus, the process is called fusion; when nuclei split to release free particles, photons (light particles), and smaller nuclei, the process is called fission. Atoms that undergo spontaneous fission are said to be radioactive.

Nuclear fusion releases all the heat produced by the sun and other stars. Nuclear fission heats the interior of Earth and is the process by which all existing nuclear power plants produce energy, although some scientists hope to harness fusion for energy production in the distant future. Since wind, waves, green plants, and sunlight are all powered by the sun (fusion) and geo-thermal heat comes from radioactive elements in Earth's core and mantle (fission), all forms of renewable energy are ultimately nuclear in origin. Nuclear fission and fusion are also used in nuclear weapons.

In a typical nuclear power plant, large, unstable atoms—most often atoms of uranium 235, whose nuclei contain 92 protons and 143 neutrons—are concentrated in a large device called a reactor. Atoms of uranium 235, like some other elements, fission spontaneously at unpredictable times. When a uranium 235 atom fissions, it releases a neutron at high speed like a subatomic bullet. If this neutron strikes another uranium nucleus, that nucleus will also fission. This reaction releases two neutrons. If there are enough uranium atoms nearby, one or both of these neutrons may strike one and cause it, too, to fission prematurely. This process continues, with neutrons from fissioned atoms causing others to fission, creating what is called a chain reaction.

A chain reaction that involves a great many atoms in a short time produces an explosion. One that levels out and causes atoms to fission in a steady flow is called a controlled chain reaction. Controlled chain reactions are the basis of nuclear power. In a nuclear reactor, the energy released by trillions of disintegrating uranium atoms (or atoms of other elements, such as thorium or plutonium) is captured by surrounding material as heat. This heat is used to boil water, and the steam from the boiling water is used to drive turbines that turn generators that produce electricity.

The reason that the reaction in a nuclear reactor can be controlled, while that in a nuclear fission bomb is not, is that in a reactor the atoms of uranium 235 are not highly concentrated. They are diluted, instead, by atoms that do not fission so easily and which therefore cannot sustain a chain reaction. Uranium 238 (92 protons, 146 neutrons) is the usual dilutant in reactor fuel. In the United States, most reactors are fueled by pellets of uranium oxide (UO₂), a black, metallic substance whose uranium consists of 3–5% uranium 235. The remainder is uranium 238. This low-enriched uranium, as it is called, is richer in uranium 235 than natural uranium ore (.7% uranium 235 and 97.3% uranium 238), but has too little uranium 235 to be used as a bomb material or to explode accidentally.

WORDS TO KNOW

BIOMASS: The sum total of living and once-living matter contained within a given geographic area. Plant and animal materials that are used as fuel sources.

ELECTRICAL BOND: Nontechnical term for the bonds that hold chemical compounds together. Such bonds (ionic or covalent) are all electrical in the sense that they depend on the attraction between positive electrical charges in atomic nuclei and negative electrical charges carried by electrons in orbitals surrounding nuclei.

FISSION: Nuclear fission is a process in which the nucleus of an atom splits, usually into two daughter nuclei, with the transformation of tremendous levels of nuclear energy into heat and light.

GREENHOUSE GASES: Gases that cause Earth to retain more thermal energy by absorbing infrared light emitted by Earth's surface. The most important greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and various artificial chemicals such as chlorofluorocarbons. All but the latter are naturally occurring, but human activity over the last several centuries has significantly increased the amounts of carbon dioxide, methane, and nitrous oxide in Earth's atmosphere, causing global warming and global climate change.

HALF-LIFE: The time it takes for half of the original atoms of a radioactive element to be transformed into the daughter product.

KILOWATT-HOUR: Amount of energy corresponding to a power flow of 1 kilowatt (1,000 watts) sustained for 1 hour. Often used as a unit of electricity consumption. A 100-watt light bulb left on for 10 hours consumes 1 kilowatt-hour (kWh). The average U.S. household purchases about 10,000 kWh of electricity per year.

NUCLEAR FUSION: The process by which two light atomic nuclei combine to form one heavier atomic nucleus. As an example, a proton (the nucleus of a hydrogen atom) and a neutron will, under the proper circumstances, combine to form a deuteron (the nucleus of an atom of “heavy” hydrogen). In general, the mass of the heavier product nucleus is less than the total mass of the two lighter nuclei. Nuclear fusion is the initial driving process of nucleosynthesis.

RENEWABLE ENERGY: Energy obtained from sources that are renewed at once, or fairly rapidly, by natural or managed processes that can be expected to continue indefinitely. Wind, sun, wood, crops, and waves can all be sources of renewable energy.

The nuclear chain reactions that produce nuclear energy do not produce greenhouse gases. This is the reason for advocating nuclear power as a way to mitigate greenhouse warming. Nuclear power can be used, its proponents say, instead of coal and natural gas to produce electricity. Coal is polluting; mining it is destructive; and it produces large amounts of carbon dioxide. Natural gas is expensive.

However, nuclear fission reactions do produce other wastes. As uranium atoms break down, atoms of other elements appear, called daughter isotopes. These, too, are unstable. Some fission quickly and others slowly. The speed with which the atoms of a given isotope (variety of an element) break down is characterized by that isotope's half-life, the time it takes, on average, for half the atoms of a certain isotope to fission spontaneously. The half-life of uranium 235, for example, is 700 million years; the half-life of plutonium 239, a breakdown product of uranium 235 that can also be used as a nuclear fuel or bomb material, is 24,100 years. Some isotopes have half-lives measured in minutes. The mixture of radioactive isotopes that accumulates in reactor fuel as the power-generating chain reaction progresses is not useful as fuel, so periodically the fuel pellets must be removed and replaced with fresh ones. The used pellets contain unused uranium 235, plutonium 239, and many other elements. This mixture, which is both chemically toxic and radioactive, is often referred to as nuclear waste.

Nuclear power generation produces nuclear waste instead of carbon dioxide. Supporters of nuclear power as a way to mitigate greenhouse warming contend that nuclear waste can be safely managed, either by some kind of reprocessing, by burial for hundreds of thousands of years beneath deserts, or both. Opponents argue that reprocessing is dangerous and expensive and that no burial scheme can be guaranteed to isolate nuclear waste from the environment for the hundreds of thousands of years needed for its radioactivity to disappear.

As of 2007, there were about 440 nuclear power plants operating in the world in 30 countries, mostly in North America and Western Europe. They produced approximately 16% of the world's electricity (6.5% of total energy demand, including non-electrical energy), varying from 80% in Lithuania (the highest), to about 20% in the United States, to 0% in many other countries. Hydroelectric power provides about the same amount of electricity worldwide. The United States, with 103 working reactors, is the world's largest producer of nuclear electricity. As of 2007, 32 nuclear plants were under construction, half of which arre in Asia. Of the last 31 nuclear reactors to begin operating up to that time, 22 were also in Asia.

History of Nuclear Power Generation

Nuclear energy was first exploited for the creation of nuclear weapons. The first such weapon was tested by the United States in 1945, and was used to destroy two Japanese cities to bring an end to World War II. The Soviet Union achieved weapons capability in 1949, the United Kingdom soon after, and France and China in the 1960s. In 1953, U.S. President Dwight Eisenhower (1890-1969) announced the “Atoms for Peace” program, whereby the United States would spread nuclear reactor technology around the world. Reactors, fissionable materials, and nuclear know-how were given away by the United States to numerous developing countries, including India, that renounced any intention to build nuclear weapons. (India became a nuclear weapons power in 1974 using nuclear material from Atoms for Peace.)

Starting in the 1950s, the United States and other countries embarked on ambitious schemes of nuclear power plant construction. In many countries, the plants were entirely owned and operated by governments, as in France and the Soviet Union. In the United States, they were purchased by utility companies with support from government tax breaks and legal guarantees against liability. Widespread public concern about nuclear power only appeared in the United States and some other countries starting in the 1970s, but nuclear power's woes were primarily economic, not political. Orders for new U.S. plants had ceased before the 1979 near-melt-down at the Three Mile Island plant in Pennsylvania; U.S. utilities had found that energy growth was slower than projected, especially after the OPEC oil embargo of 1973, and that nuclear power plants were more expensive than projected.

In the Soviet Union, nuclear plant construction proceeded under government command but was severely set back by the meltdown and explosion at the Chernobyl nuclear plant in 1986, which spread radioactive fallout over much of northern Europe and Scandinavia. In the United States, as of 2007, no new order for a nuclear plant made since 1973 had remained unconcealed. This appeared likely to change soon, however, as a result of renewed government, industry, and utility support for nuclear power.

In the early 2000s, under the presidential administration of George W. Bush, U.S. government support for nuclear power increased. The nuclear industry now plans to build 28 new reactors in the United States at a cost of about $4 to $5 billion apiece. In 2007, the Clean Energy Act of 2007, passed by both the House and Senate, contained a provision allowing the Department of Energy to give unlimited loan guarantees for any form of power generation it deems “clean.” This includes nuclear power plants under 2005 legislation because nuclear power does not emit greenhouse gases. The loan guarantees would mean that utilities could borrow money from banks to build new nuclear power plants, and that if the utilities could not pay back the loans, the federal government would do so for them. These guarantees can cover up to 80% of the cost of any single project. Although other energy sources, such as solar power and biomass, may also receive the guarantees, nuclear power is likely to receive the bulk of them because the industry is poised to begin a large number of expensive projects.

Impacts and Issues

The Case for Nuclear Power

Both government and industry sources appeal to the need to slow greenhouse warming of global climate as a primary reason to renew and accelerate the building of nuclear power plants worldwide. Advocates include international bodies tasked with the promotion of nuclear power, including the International Energy Agency, which in 2006 called for the construction of 200 new power plants over the next 24 years, and the International Atomic Energy Agency (IAEA), which in 2004 warned that without expanded nuclear construction the share of world electricity generated by nuclear power would drop from 16% to 12% by 2030. The IAEA recommended expansion of nuclear generating capacity by 2.5 times to 2030 to provide 27% of total electricity production. The UN's Intergovernmental Panel on Climate Change (IPCC) stated in its 2007 report that nuclear power “could make an increasing contribution to carbon-free electricity and heat in the future.”

Past problems with safety, reliability, waste, and high costs have been or will soon be solved, say nuclear proponents. According to Yuri Sokolov, the IAEA's deputy director general for nuclear energy: “In the longer term, new innovative designs, with shorter construction times and significantly lower capital costs could help promote a new era of nuclear power.”

According to the IAEA, nuclear power emits almost no greenhouse gases. From mining of uranium ore to disposal of nuclear waste, including construction of reactors and other facilities, the IAEA states that nuclear power emits .07-.21 ounces (2-6 g) of carbon per kilowatt-hour of electricity generated. (A kilowatt-hour is the amount of energy required for one hour by a device that consumes a thousand watts of electricity: e.g., ten 100-watt light bulbs burning for one hour consume a kilowatt-hour of electricity.) This is about as much carbon as is released during the manufacture of machinery associated with wind power and photovoltaic solar electricity. Japan and India have officially named nuclear power as part of their strategies to reduce greenhouse-gas emissions. And according to the IAEA in 2005, “in the U.S.A. and some other countries …nuclear is now the cheapest way to produce electricity.”

The Case against Nuclear Power

Opponents of the proposed increase in nuclear power plants argue that quick action is needed to reduce greenhouse gases, but nuclear power plants take approximately 10 years to build. According to the Nuclear Energy Institute's 2007 position statement, “the new nuclear power projects now in the early stages of development will not enter service until the 2015-2020 period.” In contrast, increased efficiency and renewable energy sources such as wind turbines and solar cells can be installed in months.

Opponents also argue that nuclear power is too expensive. For example, the IAEA's claim that “nuclear is now the cheapest way to produce electricity” only takes nuclear's operating costs into account, not construction, decommissioning, and waste-disposal costs, and compares nuclear power only to coal and natural gas, not to renewable sources like wind. When comparing all costs for each power source divided by all the electricity it will make over its lifetime, new nuclear costs 7 cents per kilowatt-hour in the United States (according to a 2003 study by the Massachusetts Institute of Technology) and new wind power costs about half as much.

Moreover, opponents argue, the cheapest way to keep carbon out of the air is not to generate new power at all, but to use less power by increasing end-use efficiency. According to a 2005 paper by Amory Lovins, a leading proponent of greenhouse mitigation through efficiency and small-scale power generation, each dollar spent on nuclear power actually worsens global warming because thesamemoney couldhavekepttwice as much carbon out of the air if spent on wind and up to 10 times as much if spent on efficiency. “In this sense of ‘opportunity cost’—any investment foregoes other outcomes that could have been bought with the same money—nuclear power is far more carbon-intensive than a coal plant.”

Nuclear opponents also argue that nuclear power is dangerous, spreading know-how that can be used by nations to build nuclear weapons (as Iran is presently accused of seeking to do); providing terrorists with tempting targets; and burdening future generations with radioactive wastes that can be buried but which may not stay buried for the tens of thousands of years required.

See Also Coal; Energy Contributions; Energy Efficiency; Wind Power.

BIBLIOGRAPHY

Books

Metz, B., et al, eds. Climate Change 2007: Mitigation of Climate Change: Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press, 2007.

Periodicals

Andrews, Edmund L., and Matthew L. Wald. “Energy Bill Aids Expansion of Atomic Power.” The New York Times (July 31, 2007).

Beck, Peter W. “Nuclear Energy in the Twenty-First Century: Examination of a Contentious Subject.” Annual Review of Energy and the Environment 24 (1999): 113-137.

Falksohn, Rüdiger. “New Reactors Across the Globe: A Nuclear Power Renaissance.” The New York Times (January 16, 2007).

Web Sites

Berry, Stephen, Amory Lovins, and Peter Bradford. “Nuclear Power and Climate Change.” Bulletin of the Atomic Scientists Online, March 2007-September 2007. <http://thebulletin.org/roundtable/nuclear-power-climate-change> (accessed October 28, 2007).

“The Future of Nuclear Power.” Massachusetts Institute of Technology, 2003. <http://web.mit.edu/nuclearpower> (accessed October 28, 2007).

Lovins, Amory. “Nuclear Power: Economics and Climate-Protection Potential.” Rocky Mountain Institute, September 11, 2005. <http://www.rmi.org/images/PDFs/Energy/E05-14_NukePwrEcon.pdf> (accessed October 28, 2007).

“Nuclear Energy Institute Position on Climate Change.” Nuclear Energy Institute, October 2007. <http://nei.org/keyissues/protectingtheenvironment/policybriefs/neipositiononclimatechange> (accessed October 28, 2007).

“Nuclear Energy, No Solution to Climate Change.” Greenpeace, June 22, 2007. <http://www.greenpeace.org/raw/content/usa/press-center/reports4/nuclear-energy-no-solution-to.pdf> (accessed October 28, 2007).

“Nuclear Power and Climate Change.” Agence pour l'énergie nucléaire (Nuclear Energy Agency). <http://www.nea.fr/html/ndd/climate/climate.pdf> (accessed October 28, 2007).

“Nuclear Power and Global Warming.” Union of Concerned Scientists, March 2007. <http://www.ucsusa.org/global_warming/solutions/nuclear-power-and-climate.html> (accessed October 28, 2007).

“Nuclear Power for Greenhouse Gas Mitigation.” International Atomic Energy Agency, November 2000. <http://www.iaea.org/Publications/Booklets/GreenhouseGas/greenhousegas.pdf> (accessed October 28, 2007).

Larry Gilman