Nuclear power

Nuclear power is any method of doing work that makes use of nuclear fission or fusion reactions. In its broadest sense, the term refers both to the uncontrolled release of energy, as in fission or fusion weapons, and to the controlled release of energy, as in a nuclear power plant. Most commonly, however, the expression nuclear power is reserved for the latter of these two processes.

The world's first exposure to nuclear power came when two fission (atomic) bombs were exploded over Hiroshima and Nagasaki, Japan, in August 1945. These actions are said to have brought World War II to a conclusion. After the war, a number of scientists and laypersons looked for some potential peacetime use for this horribly powerful new form of energy. They hoped that the power of nuclear energy could be harnessed to perform work, but those hopes have been realized only to a modest degree. Some serious problems associated with the use of nuclear power have never been satisfactorily solved. As a result, 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.

Words to Know

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.

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.

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

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

Neutron: A subatomic particle that carries no electrical charge.

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.

Nuclear reactor: Any device for controlling the release of nuclear power so that it can be used for constructive purposes.

Radioactivity: The property possessed by some elements of spontaneously emitting energy in the form of particles or waves by disintegration of their atomic nuclei.

Subatomic particle: Basic unit of matter and energy (proton, neutron, electron, neutrino, and positron) smaller than an atom.

Turbine: A device consisting of a series of baffles (baffles are plates, mounts, or screens that regulate the flow of something—in this case, a liquid) mounted on a wheel around a central shaft. Turbines are used to convert the energy of a moving fluid into the energy of mechanical rotation.

The nuclear power plant

A nuclear power plant is a system in which energy released by fission reactions is captured and used for the generation of electricity. Every such plant contains four fundamental elements: the reactor, the coolant system, the electrical power generating unit, and the 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 any fission reaction include not only huge amounts of energy, but also waste products, known as fission products, and additional neutrons. A constant and reliable flow of neutrons is ensured in the reactor by means of a moderator, which slows down the speed of neutrons, and control rods, which control the number

of neutrons available in the reactor and, hence, the rate at which fission can occur.

Energy produced in the reactor is carried away by means of a coolant—a fluid such as water, or liquid sodium, or carbon dioxide gas. The fluid absorbs heat from the reactor and then begins to boil itself or to cause water in a secondary system to boil. 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, powers a generator that produces electrical energy.

Safety systems. The high cost of constructing a modern nuclear power plant reflects in part the enormous range of safety features needed to protect against various possible mishaps. 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 power plant itself.

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

On another level, the whole plant itself is required to be encased within a dome-shaped containment structure. The containment structure is designed to prevent the release of radioactive materials in case of an accident within the reactor core.

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 released to the atmosphere. Additional specialized devices and systems have been developed for dealing with other kinds of accidents in various parts of the power plant.

Types of nuclear power plants. 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 (BWR) plant. In a BWR plant, coolant water surrounding the reactor is allowed to boil and form steam. That steam is then piped directly to turbines, which spin and drive the electrical generator. A very different type of plant is one that was popular in Great Britain for many years—one that used 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. There the heated carbon dioxide gas gives up its energy to water, which begins to boil and change to steam. That steam is then used to power the 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. Those concerns vary considerably from nation to nation. In France, for example, more than half of all that country's electrical power now comes from nuclear power plants. By contrast, the initial enthusiasm for nuclear power in the United States in the 1960s and 1970s soon faded, and no new nuclear power plant has been constructed in this country since the mid-1980s. Currently, 104 commercial nuclear power reactors in 31 states generate about 22 percent of the total electricity produced in the country.

One concern about nuclear power plants, of course, is the memory 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. Most experts insist that such an event is impossible. But a few major disasters continue to remind the public about the worst dangers associated with nuclear power plants. By far the most serious of those disasters was the explosion that occurred at the Chernobyl Nuclear Power Plant near Kiev in 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. Hundreds of thousands of nearby residents were exposed to deadly or damaging levels of radiation and were removed from the area. Radioactive clouds released by the explosion were detected as far away as western Europe. More than a decade later, the remains of the Chernobyl reactor were still far too radioactive for anyone to spend more than a few minutes in the area.

Critics 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 under normal circumstances is no more than that of a person living many miles away.

In any case, safety concerns in the United States have been serious enough essentially to bring the construction of new plants to a halt. By the end of the twentieth century, licensing procedures were so complex and so expensive that few industries were interested in working their way through the bureaucratic maze to construct new plants.

Nuclear waste management. Perhaps the single most troubling issue for the nuclear power industry is waste management. 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. Techniques must be developed for the destruction and/or storage of these wastes.

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 is usually satisfactory.

High-level wastes are a different matter. The materials that make up these wastes are intensely radioactive and are likely to remain so for thousands of years. Short-term methods of storage are unsatisfactory because containers would leak and break open long before the wastes were safe.

For more than two decades, the U.S. 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 caused that plan to be shelved. 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. Again, complaints by residents of Nevada and other citizens have delayed putting that plan into operation. The government insists, however, that Yucca Mountain will eventually become the long-term storage site for the nation's high-level radioactive wastes. Until then, those wastes are in "temporary" storage at nuclear power sites throughout the United States.

History

The first nuclear reactor was built during World War II (1939–45) as part of the Manhattan Project to build an atomic bomb. The reactor was constructed under the direction of Enrico Fermi in a large room beneath the squash courts at the University of Chicago. It was built as the first concrete test of existing theories of nuclear fission.

Until December 2, 1942, when the reactor was first put into operation, scientists had relied entirely on mathematical calculations to determine the effectiveness of nuclear fission as an energy source. It goes without saying that the scientists who constructed the first reactor were taking an extraordinary chance.

That first reactor consisted of alternating layers of uranium and uranium oxide with graphite 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. The moment at which Fermi directed the control rods to be withdrawn occurred at 3:45 p.m. on December 2, 1945. That date can legitimately be regarded as the beginning of the age of controlled nuclear power in human history.

Nuclear fusion power

Many scientists believe that the ultimate solution to the world's energy problems may be in the harnessing of nuclear fusion power. A fusion reaction is one in which two small 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.

The world was introduced to the concept of fusion reactions in the 1950s, when the Soviet Union and the United States exploded the first 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.

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 containing the very high temperatures produced (a few million degrees Celsius) when fusion occurs. 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.

[See also Nuclear fission; Nuclear fusion ]

nuclear energy In 1938, while working with his colleague Fritz Strassman at the laboratory in Berlin, Otto Hahn noted a special property of the element uranium-235 (²³⁵U). When bombarded by slow neutrons the nucleus of this atom split into two parts of similar mass with an emission of prodigious amounts of energy, a process known as ‘nuclear fission’ (Fig. 1). At the time the discovery was regarded as little more than a scientific curiosity, and Hahn and Strassman reported their findings in the open literature.

The fission process

It did not take long for scientists in various parts of the world to appreciate the significance of the discovery. Apart from the release of large amounts of energy and the production of fission fragments, two or three neutrons are also emitted during the fission of ²³⁵U. Normally present only within their parent nuclei, these escaping neutrons, with a diameter of only 10⁻¹⁴ metres and carrying no electrical charge, can wander freely through materials. On their scale, a solid is mainly open space but should they chance upon an atomic nucleus they may often merely bounce off. Occasionally, though, the nucleus may be entered, making it unstable and provoking radioactive change. To illustrate this process, Otto Frisch recalled that the Danish scientist Niels Bohr had suggested that the atomic nucleus may be regarded as a globular water droplet wobbling to and fro. In the case of the large uranium nucleus it could even wobble into a dumb-bell shape, from which it might occasionally split into two distinct smaller nuclei of slightly unequal size. After the disintegration of ²³⁵U, the neutrons released may strike other ²³⁵U nuclei, causing them also to undergo fission, leading to more energy release, and the emission of yet more neutrons, which can then cause further fission, and so on. The possibility therefore existed of establishing a self-sustaining chain reaction, rapidly multiplying the individual atomic-scale energy releases into a huge energy release on a macroscopic scale.

Other fates may, however, befall the neutrons released during fission of ²³⁵U. In its natural state uranium consists principally of nuclei of two isotopes: ²³⁵U (0.7 per cent) and ²³⁸U (99.3 per cent). It is thus highly probable that a neutron may be captured by the more abundant ²³⁸U nucleus, which does not disintegrate but undergoes radioactive change. This does not represent a total loss, because the capture process causes it to transmute to a useful new element. Adding a neutron, which has one unit of mass, to ²³⁸U gives ²³⁹U, which decays rapidly to a new element by emitting a beta particle. As beta decay does not change the atomic mass, the isotope of the new element number 93, neptunium, also has mass 239. Neptunium-239 is radioactive and undergoes beta decay with a half-life of 2 days to yet another new element, number 94: plutonium (Pu). Again, the isotope with the same mass, 239, is produced.

The significance of this chain of events, illustrated in Fig. 2, is that the isotope ²³⁹Pu is capable of undergoing fission, and so can be used in its own right as a nuclear fuel. We therefore have a mechanism whereby the non-fissile material ²³⁸U can be converted into a fissile material, ²³⁹Pu. We thus have the possibility of using the whole of natural uranium for energy production.

The nuclear reactor

Having seen how nuclear energy can, in principle, be produced through the process of uranium fission, it is important to see how this can be achieved in practice in a nuclear reactor. It is possible to establish a self-sustaining chain reaction using natural uranium as a fuel, and most of the early reactors did so. To give the neutrons a better chance of meeting fissile nuclei, rather than getting lost or captured without fission, later designs used ‘enriched’ uranium in which the concentration of ²³⁵U is above the natural level. Fuel elements are therefore constructed as rods of either natural or enriched uranium in either metallic or oxide form, depending on the type of reactor. The fuel rods are contained or ‘canned’ in some suitable material to prevent the fission products, some of which are gaseous, from seeping into the coolant stream. The choice of canning material is governed by its properties with respect to neutrons and by its strength and corrosion resistance. It is essential that it does not absorb too many neutrons, since this would impede the performance of the reactor. In some designs an alloy of magnesium is used; in others, an alloy of zirconium; and in yet others, stainless steel.

Neutrons are emitted from the fission process at high speeds and are better able to induce further fissions at much slower speeds. An important component of a reactor is therefore the ‘moderator’, within which the neutrons bounce to and fro off many nuclei without being absorbed, gradually losing energy of motion. It is essential that the moderator's atoms are very light and take up as much energy as possible to slow the fission neutrons to speeds approaching those of ordinary gas molecules, about 1.5 km per second. Some reactors use carbon as their moderating material in the form of graphite. Others use normal or ‘heavy’ water. The core of a reactor thus consists of a block or tank of moderator into which fuel rods are inserted.

To control the reactor (the equivalent of turning up and down a flame on a gas cooker) control rods made of boron or cadmium are inserted near the fuel rod to absorb neutrons. When the fuel rods are fully in they mop up so many neutrons that the chain reaction cannot be maintained and the reactor stops. The energy from the fission process appears as heat in the fuel rods, and this is extracted by passing a coolant over them which absorbs the heat and transfers it to a boiler in which steam is generated. From then on the hardware is identical to that of a conventional coal- or oil-fired power station. The steam is passed through turbines in which the heat energy of the steam is converted into mechanical energy of rotation. The turbines drive electrical generators which feed the public electricity grid.

The coolant can be a gas or a liquid. Some designs of reactor use carbon dioxide gas, others use water. In order to get a sufficiently high rate of heat transfer from the fuel rods, the coolant has to be pushed over them at a pressure which is many times higher than atmospheric pressure. In the pressurized water reactor (PWR), shown schematically in Fig. 3, the water is held under very high pressure in completely liquid form.

Table 1. Types of nuclear reactor

The natural reactor at Oklo

The ratio of the isotopes ²³⁵U to ²³⁸U in naturally occurring uranium deposits is virtually constant. It has been determined very accurately as 0.7202 ± 0.0006 per cent. It is also the same for the traces of uranium found in samples of lunar material collected by the Apollo missions and in meteorites.

In May 1972 however, the French scientist H. Bouzignes recorded a ²³⁵U/²³⁸U ratio of 0.7171 ± 0.0007 per cent from a uranium sample extracted from a mine at Oklo in the West African state of Gabon. Subsequent core samples revealed lower values. One was even as low as 0.296 per cent. At first it was difficult to understand why the ²³⁵U content was so low in minerals from this source, but a possible clue was to be found in the associated deviation from natural values of the isotopic ratios of other elements, such as neodymium (Nd). Natural neodymium contains 12 per cent neodymium-143, while in Oklo samples containing 24 per cent ¹⁴³Nd were identified. The only plausible explanation for this is that long ago the missing ²³⁵U fissioned, producing ¹⁴³Nd among other fission products. The volatile fragments such as iodine and the noble gases would have escaped and the easily soluble ones would have been washed away. Of special interest, though, particularly in the context of waste disposal, is the fact that that analyses showed that elements such as plutonium and the rare earths had not moved from their place of origin.

It is amazing that the random forces of nature could have conspired to create the conditions necessary for a nuclear reactor, given the degree of precision engineering needed in modern-day facilities. A detailed analysis of the isotopes of other elements in the Olko deposits, including rubidium-87 and strontium-87, revealed them to be 1740 million years old when, by virtue of their respective half-lives, the ratio of the uranium isotopes would have differed markedly from the present natural ratio. At that time the ²³⁵U content of natural uranium would have been 3.0 per cent, a sufficiently high level in the absence of neutron-absorbing materials and the presence of water to support a spontaneous continuing reaction.

Nuclear fusion

The naturally occurring atomic elements may be arranged in a series from the lightest (hydrogen, atomic number 1) to the heaviest (uranium, atomic number 92). Their nuclei are more tightly bound at the centre of this series, where the precious metals and the elements used in everyday manufacture occur. Thus at the heavy end of the series there is a tendency to split into smaller fragments, releasing energy; and by the same token it would seem likely that if nuclei of the lightest elements could be made to join or fuse together to form heavier ones, then large amounts of energy would also be produced. The latter process, illustrated in Fig. 4, is called nuclear fusion, and it is from this process that the Sun and stars derive their energy.

For fusion reactions to occur, the fuels, which are gases, must be heated to very high temperature. The atoms then become ionized, freeing the electrons which orbit the nucleus. This mixture of randomly moving electrons and nuclei is called plasma. In this state, at temperatures around 100 million °C, abundant fusion reactions occur between deuterium and tritium nuclei. These two gases, which are different forms of hydrogen, were used in the first fusion reactors.

In Europe a joint undertaking was set up to construct and operate a fusion reactor known as the Joint European Torus (JET). The machine began operation in June 1983. A schematic representation of a fusion reactor is given in Fig. 5. As plasma is a mixture of positive and negative particles, magnetic fields may be used to contain it and prevent the particles hitting the wall of the containing vacuum vessel.

During a JET experiment, a small quantity of gas is introduced into the doughnut-shaped vacuum vessel—the Torus. The gas is heated to form a plasma by the passage of a large electric current of up to 5 million amperes (5 MA). This plasma current also produces a magnetic field which combines with a second field produced by 32 D-shaped coils equally spaced around the vacuum vessel. This complex system of magnetic fields, called a TOKAMAK (a Russian acronym for toroidal magnetic chamber), provides a cage that prevents the hot plasma from hitting the walls of the vacuum vessel. A set of six hoop coils around the outside of the machine produces the magnetic field that shapes and positions the plasma centrally in the torus.

Fusion reactor

Should the JET experiments ultimately lead to the construction of a commercial reactor, the neutrons produced during the fusion reactions would be captured by a blanket surrounding the plasma region. This blanket would almost certainly contain lithium to produce the tritium needed in the reaction. It is also envisaged that the neutrons so captured would heat up the blanket to temperatures in the region of 500 °C so that steam could be raised to drive turbines and generate electricity in the normal manner.

Geoffrey C. Allen

NUCLEAR POWER

NUCLEAR POWER refers to the energy produced by fission, when atoms are split, or by fusion, when two nuclei of a light atomare fused to forma single nucleus. The energy produced can be used for weapons or for peaceful purposes. The phrase is also used to designate those nations that have nuclear weapons. The first five nations to declare that they had nuclear weapons were the United States (1945), the former Soviet Union (1949), Great Britain (1952), France (1960), and China (1964), known as the "Big Five." The breakup of the Soviet Union in the early 1990s resulted in the addition of Belarus, Kazakhstan, and Ukraine as nuclear-weapon states because the nuclear missiles and storage sites placed on their territory by the Soviet Union became the property of these newly independent states; all three, however, transferred their weapons to Russia. India conducted its first nuclear test in 1974, followed by Pakistan in 1998. North Korea is believed to have the capacity to develop nuclear weapons within a short time. Others, such as Israel, have likely developed one or more such weapons secretly. Some analysts believe that another group of countries, including Iraq, were trying to develop nuclear weapons at the turn of the twenty-first century.

Nuclear power also refers to plants and industry that generate electric power from nuclear sources. The possibility of using the energy in the atomic nucleus as a power source was widely recognized soon after the discovery of nuclear fission late in 1938, but only the United States was able to devote any significant effort to atomic energy development during World War II. On 2 December 1942 Enrico Fermi and others achieved the first self-sustained chain reaction at Stagg Field at the University of Chicago. This experiment made possible the construction of three large plutonium-producing reactors; each generated about 250,000 kilowatts of energy, but they were not used for electric power production.

Despite the initial popular belief that the use of nuclear power was imminent, technical progress was slow after the war. The U.S. Atomic Energy Commission (AEC), facing extreme shortages of uranium ore, supported only three small reactor projects before 1950. One of these, the Experimental Breeder Reactor No. 1, succeeded in generating a few kilowatts of electric power late in 1951, an accomplishment more symbolic than practical.

Growing industrial interest in nuclear power by 1952, basic revision in atomic energy legislation in 1954, and increasing ore supplies made a more ambitious program possible in the 1950s. The AEC adopted a five-year plan designed to test the feasibility of five different reactor systems. One of these, the pressurized water reactor (PWR)—designed and and built by a joint AEC-Navy tea munder Rear Adm. H. G. Rickover, at Shippingport, Pennsylvania—produced 60,000 kilowatts of electricity for commercial use before the end of 1957. The AEC's Argonne National Laboratory, at Lemont, Illinois, under Walter H. Zinn, successfully developed the experimental boiling water reactor (EBWR). The PWR and EBWR committed the United States almost exclusively to water-cooled reactors for the next two decades. By the end of 1957, the AEC had seven experimental reactors in operation, and American industry had started nine independent or cooperative projects expected to produce 800,000 kilowatts of electricity by the mid-1960s.

Nuclear power plants differ from hydroelectric plants—which generate electricity from the force of flowing water—and from coal-, oil-, or gas-fired electric plants, which generate electricity from the heat drawn from burning fossil fuels. Nuclear power plants generate steam to drive electric turbines by circulating liquid through a nuclear reactor. The reactor produces heat through the controlled fission of atomic fuel. Normally the fuel for power reactors is slightly enriched uranium. These differences give nuclear reactors several advantages over power generation using other fuels. Unlike fossil fuels, nuclear fuel does not foul the air and is not dependent on oil imports from unstable parts of the world. Before the environmental effects of radioactive wastes and the safety hazards of nuclear plants became apparent in the 1960s and 1970s, some environmentalists were strong advocates of nuclear power as a "clean" energy source. Others, aware of the rising costs of the world's diminishing coal, oil, and natural gas resources and the limitation on the number of hydroelectric power plants that could be built, believed that nuclear plants could be the key to an independent American energy supply.

The attraction of electricity generated by nuclear power was not limited to the United States. In contrast to the American emphasis on water-cooled reactors, both the United Kingdom and France chose to rely on gas-cooled systems. By 1957 the United Kingdom was building or planning twelve reactors with a capacity of more than 1 million kilowatts; the French were building five reactors totaling more than 350,000 kilowatts. The Soviet Union was planning a 200,000-kilowatt PWR and two smaller boiling-water reactors. By 1966 nuclear power generators were being built or operating in five countries. By 1980 there were a hundred nuclear power plants in the United States.

Technical difficulties prevented any of these national plans from being realized by the early 1960s. In the United States the AEC countered the resulting pessimism

by predicting the imminence of economically competitive nuclear power and concentrating resources on the most promising reactor designs—water-cooled reactors for the immediate future and sodium-cooled breeder reactors for later decades in the century. This confidence was fulfilled by early 1964, when an American power company first announced its decision, on the basis of economics alone, to construct a nuclear power plant. Despite a temporary dampening effect of licensing delays and challenges from environmentalists protesting the dumping of radioactive wastes, the trend toward nuclear power accelerated again in the early 1970s. By the fall of 1972, the total nuclear gross generating capacity of all nations outside the Communist bloc had reached 32 million kilowatts. Of this total, the United States provided 13 million electrical kilowatts generated in twenty-eight operating plants. More than a hundred additional plants with a total capacity of more than 116 million kilowatts had been ordered or were under construction in the United States.

A serious accident at Three Mile Island in 1979 proved to be a major turning point for nuclear power in the United States, and no new nuclear generators have been ordered since. All of the increases in nuclear-generated electricity since 1979 have come from existing plants, which have boosted their national capacity factor from under 65 percent in 1970 to 76 percent in 1996.

One of the byproducts of nuclear-power generation is plutonium, a material that can be chemically processed for use in nuclear weapons. The danger of such use by nonnuclear nations led to international safeguards under the 1968 Nuclear Nonproliferation Treaty. In Article III signatory nations agreed to inspections by the International Atomic Energy Agency (IAEA), "with a view to

preventing diversion of nuclear energy from peaceful uses to nuclear weapons or other nuclear explosive devices." Most of the world's nuclear and nonnuclear nations signed this treaty. Iraq in 1992 and North Korea in 1994 were subjected to IAEA inspections that proved treaty violations in the former and raised serious suspicions about the latter. Both nations were signatories of the treaty, although North Korea announced its withdrawal some months prior to inspection. Iraq's nuclear-weapon production facilities were discovered as a result of a series of highly intrusive IAEA inspections and were subsequently destroyed by the United Nations.

When Congress passed the Atomic Energy Act of 1954, it approved President Dwight D. Eisenhower's Atoms for Peace program, which included commercial development of nuclear reactors for the purpose of generating electric power. During the 1960s electricity generated by nuclear power contributed 1 to 2 percent of the nation's energy total. Since then that percentage has grown steadily, surpassing the proportion from hydroelectric sources in 1984.By 1990 nuclear power amounted to one-fifth of the nation's total generation of electricity. By 1992 nuclear generation reached 619 billion net kilowatt hours, more than double the amount generated in 1979, the year of the Three Mile Island accident.

In reaction to the 1973 oil embargo, U.S. consumers temporarily used less energy, which diminished the rate of growth in electricity generation. As a result of this and other factors, such as higher construction costs, delays brought on by antinuclear protests, increased operating costs resulting from new federal regulations, and uncertainties about disposal of high-level radioactive waste, no requests for construction of new nuclear power plants have been received by the Nuclear Regulatory Commission since 1978.The level of generation was still rising, however, because plants started in the 1970s had gone on-line, and modernization after 1979 made power plants more efficient. The rising production trend continued until the end of the twentieth century; in the year 2000, for example, 104 commercial nuclear plants in the United States produced 20.5 percent of all electricity consumed in the United States. Nuclear power's future is far from clear, however. The Energy Information Administration projected in 2001 that 27 percent of the nation's nuclear generating capacity then in existence would be retired by 2020, with no construction of new plants anticipated.

BIBLIOGRAPHY

Department of Energy, Energy Information Administration. Annual Energy Outlook 2002 with Projections to 2020. Washington, D.C.: Department of Energy, 2001.

Deudney, Daniel, and Christopher Flavin. Renewable Energy: The Power to Choose. New York: W.W. Norton, 1983.

Duffy, Robert J. Nuclear Politics in America: A History and Theory of Government Regulation. Lawrence: University Press of Kansas, 1997.

Henderson, Harry. Nuclear Power: A Reference Handbook. Santa Barbara, Calif.: ABC-CLIO, 2000.

Robert M.Guth

Richard G.Hewlett/c. w.

See alsoNuclear Non-Proliferation Treaty (1978) ; Nuclear Test Ban Treaty .

NUCLEAR RESEARCH

Fermi Achieves the First Chain Reaction

In late 1942—in a squash court under the stands of Stagg Field, the unused University of Chicago football stadium—a group of physicists led by Enrico Fermi, who had received the 1938 Nobel Prize in physics for his work with radioactivity, constructed a chain-reacting nuclear pile with six tons of uranium metal and fifty tons of uranium oxide encased in four hundred tons of graphite. On 2 December Fermi slowly withdrew the reaction-control rods. As the clicks of neutron counters increased steadily, reminding those present of "a mounting frenzy of crickets," Fermi announced that the pile had reached critical mass, that is, enough material in the pile had become radioactive to create a chain reaction by means of nuclear fission (the splitting of the atomic nucleus). Thus, he achieved the first controlled release of nuclear energy.

Nuclear Physics and the War Effort

The Japanese bombing of Pearl Harbor on 7 December 1941 and the subsequent entrance of the United States into World War II had added a sense of urgency to nuclear research. Amid fears that the Germans might be building an atomic bomb, President Franklin D. Roosevelt authorized the Manhattan Project, a top-secret, large-scale effort to build an atomic bomb within three years.

The Manhattan Project

This huge project was sponsored by the Office of Scientific Research and Development (OSRD), a government agency formed in June 1941 to oversee and coordinate wartime scientific research under the direction of electrical engineer and physicist Vannevar Bush. By late December 1942 Roosevelt had authorized $400 million for the Manhattan Project, headed by Gen. Leslie R. Groves. Involving a huge team of scientists from many disciplines and the U.S. Army Corps of Engineers, the Manhattan Project secretly constructed a plutonium-generating reactor at Hanford, Washington; a gas-diffusion facility at Oak Ridge, Tennessee; and a physics research laboratory at Los Alamos, New Mexico. Under the direction of Berkeley physicist J. Robert Oppenheimer, the Los Alamos team set out to design and build bombs from the materials produced by Hanford and Oak Ridge. They faced the technical problem of how to amass fissionable material and shape it into a workable bomb. By March 1944 the Oak Ridge experiments yielded the first milligrams of plutonium, and by early 1945 the Hanford facilities began turning out pure plutonium.

[This text has been suppressed due to author restrictions]

To Build the Bomb

The Los Alamos scientists had to understand critical-mass behavior in order to design a workable bomb. That is, they had to find out how a critical mass of uranium 235 or plutonium would behave in the split second between the start of the chain reaction and the resulting explosion. They also had to avoid the predetonation of the plutonium. Solving these problems represented a formidable challenge. The solution was an implosion bomb: they surrounded a mass of subcritical plutonium with high explosives that, when detonated, produced a spherically symmetrical shock wave traveling toward the center of the bomb. The shock wave compressed the plutonium into a critical mass and kept it compressed while a rapid chain reaction occurred, maximizing energy release while avoiding predetonation.

The Trinity Test

On 16 July 1945 at Alamogordo, two hundred miles from the Los Alamos weapons lab, scientists tried out the first plutonium device. The explosion lit the predawn desert sky and shook the earth with the power of twenty thousand tons of dynamite. The atomic age had begun.

Hiroshima and Nagasaki

On 6 August 1945 the American Superfortress bomber Enola Gay dropped a uranium bomb called "Little Boy" on Hiroshima, Japan, killing more than fifty thousand people and totally destroying four square miles of the city. Three days later another American bomber dropped "Fat Man," a plutonium bomb, on Nagasaki, killing more than forty thousand and destroying a third of the city. The Japanese surrendered the next day.

Scientific Responsibility

Many scientists were deeply troubled by their role in creating the atomic bomb and led efforts to persuade Congress of the importance of arms control. Physicist Eugene Rabinowitch committed himself to "fight to prevent science from becoming an executioner of mankind." Many liberal scientists also wanted the United States to share atomic-energy secrets with the rest of the world and establish a system of United Nations control. Yet, according to a September 1945 survey, 75 percent of the American people wanted the United States to retain control of the bomb. Efforts at international control failed in the late 1940s, as the United States adopted a defensive Cold War outlook toward the Soviet Union and other Communist nations.

A Shift in Public Opinion

The atomic bombings of Japan were denounced in liberal religious circles as cause for "American shame." Most people were ambivalent, relieved that war had ended but fearful that perhaps science had finally gone too far. Early polls revealed that the public overwhelmingly backed the use of atomic bombs against Japan because it brought the war to a speedy end. In a September 1945 Gallup poll 65 percent of respondents agreed with the statement that the development of the atomic bomb was "a good thing." Yet public response changed dramatically as time passed. By October 1947 only 55 percent continued to affirm that it was a good thing, while those who considered the bomb "a bad thing" more than doubled, from 17 percent in 1945 to 36 percent in 1947.

Health Hazards

As early as 1947 there were concerns about the health hazards of radiation research. Military researchers pressed for radiation experiments on humans, while physicians and biologists warned of the possible dangers. Dr. Shield Warren, chief medical officer of the Atomic Energy Commission (AEC), said in July 1949 that he was "taking an increasingly dim view of human experimentation." Later that year the Joint Panel on the Medical Aspects of Atomic Warfare was established to monitor atomic research in the U.S. Defense Department. Minutes of one panel meeting made public in 1994 expressed awareness that if ethical rules were adopted "then obviously a great deal of our present human tracer studies must be discontinued." The minutes reported that there were "ethical and medico-legal objections to the administration of radioactive materials without the patients' knowledge or consent," and they expressed the concern that there would be even greater government culpability "if a Federal agency condones human guinea pig experimentation." Yet the U.S. Defense Department circumvented the objections of the AEC, and hundreds of people were irradiated—most often in the thyroid gland—in medical experiments conducted during the late 1940s and 1950s.

The Hydrogen Bomb

Despite the objections of scientists and public fears, government policy makers pressed for the development of further nuclear weapons and prevailed. Physicist Edward Teller, who had been involved in the Manhattan Project, passionately supported the development of a hydrogen bomb, a device that works by fusion—the creation of an atomic nucleus by the union of two lighter nuclei. Deriving its power from the same process that creates the heat and light of the sun, a hydrogen or thermonuclear bomb is a super-bomb a thousand times more powerful than the bombs dropped on Hiroshima and Nagasaki. The question of developing the hydrogen bomb rested with the general advisory committee of the AEC, established by the 1946 Atomic Energy Act. Many top scientists, led by Fermi and Oppenheimer, opposed developing the hydrogen bomb, arguing that scientists had not always behaved responsibly in nuclear research. Five of six scientists on the AEC advisory board felt that developing the super-bomb could spark an uncontrollable arms race and that the only hope for world peace lay in refusing to allow development of the bomb. Yet President Harry S Truman was concerned that the Russians were developing nuclear weapons (they exploded an atomic bomb in 1949), and in 1950 he authorized a crash program to build the hydrogen bomb.

Creation of the National Science Foundation. It was clear that in the atomic age it had just entered, the United States needed to establish national policies to govern scientific, especially nuclear, research. Scientists, academic leaders, and policy makers were concerned that the freedom of pure scientific research would be compromised by financial ties to industry and the military. Scientists, congressional leaders, and many in the Truman administration believed that the best way to halt the military's increasing role in academic science was for Congress to create the National Science Foundation (NSF). Under the direction of scientists, the NSF would plan a federally mandated scientific research program. Truman vetoed the original 1947 legislation because he wanted the agency to be controlled directly by the president, not by a board of scientists. After compromise legislation, which allowed for shared presidential and scientific control, the act establishing the NSF was passed by Congress and signed by President Truman in March 1950. The NSF provided federal support for basic scientific training and research that was largely insulated from political interests and dedicated to the advancement of science.

Sources:

Barton J. Bernstein, "Roosevelt, Truman, and the Atomic Bomb: A Reinterpretation," Political Science Quarterly, 90 (Spring 1975): 23-69;

Paul Boyer, By the Bomb's Early Light: American Thought and Culture at the Dawn of the Nuclear Age (New York: Pantheon, 1985);

Arthur Holly Compton, Atomic Quest: A Personal Narrative (New York: Oxford University Press, 1956);

Leslie R. Groves, Now It Can Be Told: The Story of the Manhattan Project (New York: Harper, 1962);

Daniel Kevles, The Physicists: The History of a Scientific Community in Modern America (New York: Knopf, 1978);

Martin J. Sherwin, A World Destroyed: The Atomic Bomb and the Grand Alliance (New York: Knopf, 1975).

NUCLEAR POWER

A form of energy produced by an atomic reaction, capable of producing an alternative source of electrical power to that supplied by coal, gas, or oil.

The dropping of the atom bomb on Hiroshima, Japan, by the United States in 1945 initiated the atomic age. Nuclear energy immediately became a military weapon of terrifying magnitude. For the physicists who worked on the atom bomb, the promise of nuclear energy was not solely military. They envisioned nuclear power as a safe, clean, cheap, and abundant source of energy that would end society's dependence on fossil fuels. At the end of world war ii, leaders called for the peaceful use of nuclear energy.

Congress passed the Atomic Energy Act of 1946 (42 U.S.C.A. §§ 2011 et seq.), which shifted nuclear development from military to civilian government control. Very little development of commercial nuclear power occurred from 1946 to 1954 because the 1946 law maintained a federal government monopoly over the control, use, and ownership of nuclear reactors and fuels.

Congress amended the Atomic Energy Act in 1954 (68 Stat. 919) to encourage the private commercial development of nuclear power. The act ended the federal government's monopoly over nonmilitary uses of nuclear energy and allowed private ownership of reactors under licensing procedures established by the Atomic Energy Commission (AEC). Private power companies did not rush to build nuclear power plants because they feared the financial consequences of a nuclear accident. Congress responded by passing the Price-Anderson Act of 1957 (42 U.S.C.A. § 2210), which limited the liability of the nuclear power industry and assured compensation for the public. With the passage of the Price-Anderson Act, power companies began to build nuclear plants.

At first, nuclear power was attractive largely because the demand for electricity grew at a steady rate in the 1960s and coal-burning facilities were becoming an environmentally unacceptable alternative. The high price of oil during the mid-1970s continued to make nuclear power economically desirable and helped keep nuclear energy a prominent part of national energy plans. By the 1990s, approximately 110 nuclear plants were operating in the United States, supplying 20 percent of the nation's electricity.

A nuclear reactor produces energy through a chain reaction that splits a uranium nucleus, releasing energy in the form of heat. Fast breeder reactors, which use plutonium as fuel, generate more energy than they expend. Plutonium is not a natural element. It must be recycled from the excess uranium produced from a chain reaction. The radioactivity of plutonium is higher and its life is longer than that of any other element. Because of these characteristics, the public became concerned about the safety of its development and use.

Until 1969, the AEC did not have a formal process for evaluating the environmental impact of building nuclear power plants. In that year Congress passed the national environmental policy act of 1969 (42 U.S.C.A. §§ 4321– 4370), which required environmental impact statements for all major federal activities. In the 1970s, the temper of nuclear regulation changed. People were no longer complacent about nuclear power safety or convinced by environmental claims made by industry and government.

This lack of public trust centered on the role of the AEC as both a promoter of nuclear technology and a regulator of the nuclear power industry. In 1974, realizing the cross purposes of promotion and safety, Congress passed the Energy Reorganization Act (42 U.S.C.A. §§ 5801–5879), which created two agencies with different missions. The nuclear regulatory commission (NRC) is an independent agency

responsible for safety and licensing. The Energy Research and Development Administration (ERDA), later absorbed into the energy department, is responsible for promotion and development of nuclear power. This alignment did not completely remove fundamental regulatory conflict for the NRC, because the agency is responsible both for licensing plants and for safety oversight. If the NRC is too vigorous in exercising its safety role, the resulting compliance costs act as a disincentive to invest in nuclear plants.

A nuclear facility cannot be built without a construction permit issued by the NRC. An environmental impact statement that assesses the effect the facility will have on the environment must also be filed with the environmental protection agency (EPA). Once built, a nuclear plant must operate pursuant to a license from the NRC. A license requires that the facility use the lowest levels of radiation necessary to reasonably and efficiently maintain operations. The NRC also issues licenses for the use of nuclear materials, for transportation of nuclear materials, and for the export and import of nuclear materials, facilities, and components.

Nuclear power regulation is highly centralized in the federal government when nuclear safety and radiological hazards are at issue. States may address the financial capability of power companies to dispose of waste and may define state tort liability for injuries suffered at nuclear facilities.

Public confidence in the nuclear power industry suffered a major blow in 1979 when an accident occurred at the Three Mile Island Nuclear Station near Harrisburg, Pennsylvania. No one was hurt during the accident although radioactive gases escaped through the plant's ventilating system. The accident did reveal, however, the nuclear power industry's lack of emergency preparedness. Following the incident, the NRC increased safety inspections, stepped up enforcement, required the retrofitting of systems to enhance safety, and developed emergency preparedness rules. These regulations delayed the opening of new nuclear plants during the early 1980s.

In 1986, however, the safety of nuclear power again was challenged when a nuclear reactor exploded at Chernobyl in the Ukraine. Radiation 50 times higher than that at Three Mile Island exposed people nearest the reactor, and a cloud of radioactive fallout spread to Western Europe, causing the deaths of more than 30 people. People the world over questioned the logic of using such a volatile energy source.

Nuclear power also became less attractive to energy companies in the 1980s. The problem of disposing of nuclear waste became the focal point for the industry. Congress passed the Nuclear Waste Policy Act of 1982 (42 U.S.C.A. §§ 10101-10226), which directed the Department of Energy to formally begin planning the disposal of nuclear wastes and imposed most of the costs of disposal on the industry. The escalating costs of waste disposal helped bring construction of new nuclear facilities to a stop.

The problem of what to do with nuclear waste has proved difficult to solve. Nuclear material is contained in fuel rods. When spent fuel rods and other waste products fill the storage capacity at utility plants, the plants must either expand their storage capacity or find permanent off-site storage. Developing permanent nuclear waste sites is imperative because nuclear waste continues to accumulate. In addition, more than one hundred of the nuclear power facilities must be permanently shut down between 2010 and 2025 because their equipment and infrastructure will no longer be safe. This will entail removing most radioactive elements within each plant's nuclear reactor and then razing the entire plant.

The federal government has encountered political controversy and public opposition in its attempt to identify potential permanent nuclear waste sites. Since 1986 it has been unsuccessful in finding an acceptable site. Yucca Mountain, Nevada, has been earmarked as a nuclear waste repository, against the objections of citizens of Nevada and other advocacy groups. In January 2002, Secretary of Energy Spencer Abraham sent a letter to Nevada Governor Kenny C. Guinn notifying Guinn that Abraham had recommended to President george w. bush the development of the Yucca Mountain site. Guinn responded that the decision was premature and that further testing was necessary. When Bush approved the development of the site, Guinn vetoed, thus sending the issue to Congress.

The House and Senate both passed resolutions in 2002 with significant majorities approving the development of the Yucca Mountain site. The Energy Department must apply for a license from the NRC in order to construct the site; the application is not expected to be filed until 2004. The state of Nevada filed lawsuits against Abraham, President Bush, the DOE, the NRC, and the Environmental Protection Agency, seeking to block the future development of this site.

The commercial prospects for nuclear energy have faded. The decommissioning of nuclear plants in the early twenty-first century will be a huge undertaking. The cost, per plant, will be more than one billion dollars. Utility customers will pay for the costs in higher utility rates, but power companies will have to devote significant amounts of time, energy, and money to complete the process.

further readings

"Nevada Yucca Mountain Lawsuits." Yucca Mountain: Eureka County Nuclear Waste Page. Available online at <www.yuccamountain.org/court/lawsuits.htm> (accessed August 9, 2003).

cross-references

Energy Department; Environmental Law; Public Utilities; Solid Wastes, Hazardous Substances, and Toxic Pollutants.

NUCLEAR POWER

A Deceiving Calm

During the 1980s proponents of nuclear power had much to celebrate. The technology worked, and it did so without burning up the earth's coal and oil reserves and without spewing noxious fossil-fuel pollutants from conventional power plants into the atmosphere. By 1989 there were 426 nuclear power plants worldwide, and the 110 plants located in the United States that year supplied nearly one-fifth of the nation's electricity. All, however, was not well in the nation's nuclear power industry.

A Torrent of Problems

The nuclear power industry in the United States was beset with problems. During the 1980s not one new order was placed for a nuclear power plant anywhere in the country. Cost overruns in construction and maintenance of reactors was much higher than had been anticipated. It was not uncommon for the final price tag of a nuclear plant to exceed tenfold the initial estimates. Safety, too, was a major concern. The events of 28 March 1979 at Three Mile Island, Pennsylvania—two hundred thousand citizens fled the region when severe core damage in one of the site's reactors was reported to be nearing a dreaded meltdown—had shaken public confidence in the industry. The issue of what to do with spent nuclear fuel rods—the used-up, highly radioactive isotopes at the heart of the reactors—also plagued the industry. These problems, coupled with an unanticipated reduction in the growth of demand for electricity nationwide (experts had predicted that demand for electricity would grow at the rate of about 7 percent annually, but in 1981 demand was up only 0.3 percent, and in 1982, amid a national campaign to conserve energy, demand actually fell by 2.3 percent), resulted in a major setback for those who had envisioned meeting half of the country's electrical demand with nuclear power by the end of the century.

Generating Electricity

A nuclear power plant is something like a giant tea kettle. The intense thermonuclear reaction at its heart is used to boil water. The controlled fission reaction at the reactor's core gives off extraordinary amounts of heat. Water passed nearby the core absorbs the heat and turns to steam, which is then used to generate electricity. By focusing high-pressure steam onto the blades of a turbine, they can spin the turbine's coils of wire through giant magnetic fields. The result is the electricity that illuminates otherwise darkened streets, powers air conditioners on sultry summer nights, energizes computers, and serves the nation in many other ways. The tricky part is boiling the water. In conventional power plants water is boiled by burning coal or oil. What attracts engineers to nuclear power is the fact that fission can provide a trillion times more energy than a windmill and a million times more energy than the combustion process at the center of conventional coal, gas, or oil power plants. The use of fission to boil water is, however, fraught with problems. Even a minuscule amount of highly radioactive uranium is deadly.

Nuclear Disaster at Chernobyl

Though thousands of miles away from America's shores, the events of 26 April 1986 near the town of Pripyat in the Soviet Union focused concern once again on the issue of safety in the nuclear power industry. One of four nuclear reactors at the Chernobyl Nuclear Power Station in the Ukraine exploded with such force that the roof of the building was completely blown off. Eight tons of radioactive material was scattered about the region immediately surrounding the plant. Airborne radioactivity from the blast rained down on northern Europe and Scandinavia—fallout was measured as far away as Scotland—contaminating farm produce. Engineers at Chernobyl had accidently initiated an uncontrolled chain reaction in the reactor's core during an unauthorized test in which they unlawfully incapacitated the reactor's emergency systems. In the immediate aftermath of the catastrophe, more than thirty people lost their lives, and one estimate placed the number who would eventually live shortened lives as a result of the effects of their exposure to radiation from the accident at twenty thousand.

Reaction

In the United States experts argued that the disaster at Chernobyl was not pertinent to the domestic nuclear industry. They noted that the technology employed at Chernobyl was not being used in the United States. The Soviets, they pointed out, were using a weapons-material production reactor to generate electricity for their domestic market—something not done in the United States. Furthermore, the Chernobyl reactor lacked a containment building—a required safety component mandated for all U.S. reactors. Nevertheless, many Americans drew uneasy parallels between Chernobyl and Three Mile Island: operator error and equipment failure were possible in the nuclear industry. The consequences of a single major mistake could be catastrophic.

Seabrook and Shoreham

Both proponents and opponents of nuclear power persistently articulated their views—sometimes in strident tones—during the 1980s. Proponents hailed the small number of nuclear power plant safety violations. Opponents pointed out that a single mistake could be extremely costly both in environmental and human terms. During the 1980s scores of "anti-nuke" organizations warned of the hazards of nuclear energy and protested plant construction and operation. In Seabrook, New Hampshire, protesters rallied around a citizens' action group—the Clamshell Alliance—to oppose the building of two nuclear reactors. By 1987, in part due to the increased vigilance of oversight safety committees insisted upon by the Clamshell Alliance, the utility that owned Seabrook was near bankruptcy. At Long Island's Shoreham nuclear facility the story was much the same. By 1988, besieged by civic-group opposition, the Shoreham "nuke," having far exceeded initial cost estimates of $241 million (its actual cost to the utility had surpassed $5 billion), was closed by the state government. The utility that owned Shoreham had failed to develop an adequate evacuation plan of that region of Long Island that would be affected in the event of a meltdown. Sold to the state government for one dollar, the completed plant was to be dismantled even before it opened.

Cost Overruns, Problematic Workmanship

Repeatedly the industry discovered that cost overruns and construction problems were an issue. Florida's St. Lucie 2 plant cost about four times its original estimate of $360 million, but this price, as it would turn out, was a relative bargain. By middecade Michigan's Midland nuclear power plant (initial cost estimate: $267 million) had cost the utility constructing it $4.4 billion, and it was nine years behind schedule. In the West, at the Diablo Canyon Plant, earthquake supports were installed backward. At the Shoreham reactor workers had to craft makeshift elbow joints when, during construction, they discovered that pipes failed to meet at the proper point. As one commentator noted, it was no wonder that problems cropped up, because constructing a nuclear plant was "like building a giant Swiss watch" using subcontractors.

The Problem of Disposal

Reactors in the 1980s were inefficient. Only about 1 percent of the uranium atoms in the rods fission; the remaining 99 percent of the uranium remains in the rods even after they are no longer useful for producing power. The pellets of uranium, which are packed into long rods and lowered into the core of a nuclear reactor, remain extremely radioactive even after they are "spent," and remain so for thousands of years. These irradiated fuel rods must be disposed of, but no one wants them in his backyard. During the 1980s utility companies stored these rods on site, at the power plants, in large vats resembling swimming pools, but this was considered a temporary solution. In 1982 Congress passed the Nuclear Waste Policy Act. The act called upon the Department of Energy (DOE) to find a suitable site to bury the radioactive waste. DOE, however, was unsuccessful in locating a site that included both the necessary stable rock formation (free of groundwater) and the requisite local public support. At decade's end, no solution to the problem of nuclear waste had been found.

Sources:

"Energy from Nuclear Power," Scientific American, 263 (September 1990): 136-142;

"The $5 Billion Nuclear Waste," Time, 131 (6 June 1988): 55;

"Memories of a Near Meltdown," Time, 123 (13 February 1984): 41;

"Pulling the Nuclear Plug," Time, 123 (13 February 1984): 34-38;

"We are in a Heap of Trouble," Time, 130 (26 October 1987): 114.

nuclear energy the energy stored in the nucleus of an atom and released through fission, fusion, or radioactivity . In these processes a small amount of mass is converted to energy according to the relationship E = mc² , where E is energy, m is mass, and c is the speed of light (see relativity ). The most pressing problems concerning nuclear energy are the possibility of an accident at a nuclear reactor or fuel plant, such as those which occurred at Three Mile Island (1979), Chernobyl (1986), and Takaimura, Japan (1999), and the potential threat to the continued existence of the human race posed by nuclear weapons (see disarmament, nuclear ).

Nuclear Reactions

The release of nuclear energy is associated with changes from less stable to more stable nuclei and produces far more energy for a given mass of fuel than any other source of energy. In fission processes, a fissionable nucleus absorbs a neutron, becomes unstable, and splits into two nearly equal nuclei. In fusion processes, two nuclei combine to form a single, heavier nucleus. The most stable nuclei—those with the highest binding energies per nucleon holding their components together—are in the middle range of atomic weights, with the maximum stability at weights near 60. Thus, fission, which produces two lighter fragments, occurs for very heavy nuclei, while fusion occurs for the lightest nuclei.

Nuclear Fission

The process of nuclear fission was discovered in 1938 by Otto Hahn and Fritz Strassmann and was explained in early 1939 by Lise Meitner and Otto Frisch. The fissionable isotope of uranium, U-235, can be split by bombarding it with a slow, or thermal, neutron. (Slow neutrons are called "thermal" because their average kinetic energies are about the same as those of the molecules of air at ordinary temperatures.) The atomic numbers of the nuclei resulting from the fission add up to 92, which is the atomic number of uranium. A number of pairs of product nuclei are possible, with the most frequently produced fragments being krypton and barium.

Since this reaction also releases an average of 2.5 neutrons, a chain reaction is possible, provided at least one neutron per fission is captured by another nucleus and causes a second fission. In an atomic bomb , the number is greater than 1 and the reaction increases rapidly to an explosion. In a nuclear reactor , where the chain reaction is controlled, the number of neutrons producing additional fission must be exactly 1.0 in order to maintain a steady flow of energy.

Uranium-235, which occurs naturally as one part in 140 in a natural mixture of uranium isotopes, is not the only material fissionable by thermal neutrons. Uranium-233 and plutonium-239 can also be used but must be produced artificially. Uranium-233 is produced from thorium-232, which absorbs a neutron and then undergoes beta decay (the loss of an electron). Plutonium-239 is produced in a similar manner from uranium-238, which is the most common isotope of natural uranium. The average energy released by the fission of uranium-235 is 200 million electron volts, and that released by uranium-233 and plutonium-239 is comparable. Fission can also occur spontaneously, but the time required for a heavy nucleus to decay spontaneously by fission (10 million billion years in the case of uranium-238) is so long that induced fission by thermal neutrons is the only practical application of nuclear fission. However, spontaneous fission of uranium can be used in the dating of very old rock samples.

The development of nuclear energy from fission reactions began with the program to produce atomic weapons in the United States. Early work was carried out at several universities, and the first sustained nuclear chain reaction was achieved at the Univ. of Chicago in 1942 by a group under Enrico Fermi. Later the weapons themselves were developed at Los Alamos, N.Mex., under the direction of J. Robert Oppenheimer (see Manhattan Project ).

Nuclear Fusion

Nuclear fusion, although it was known theoretically in the 1930s as the process by which the sun and most other stars radiate their great output of energy, was not achieved by scientists until the 1950s. Fusion reactions are also known as thermonuclear reactions because the temperatures required to initiate them are more than 1,000,000°C. In the hydrogen bomb , such temperatures are provided by the detonation of a fission bomb. The energy released during fusion is even greater than that released during fission. Moreover, the fuel for fusion reactions, isotopes of hydrogen, is readily available in large amounts, and there is no release of radioactive byproducts.

In stars ordinary hydrogen, whose nucleus consists of a single proton, is the fuel for the reaction and is fused to form helium through a complex cycle of reactions (see nucleosynthesis ). This reaction takes place too slowly, however, to be of practical use on the earth. The heavier isotopes of hydrogen— deuterium and tritium —have much faster fusion reactions.

For sustained, controlled fusion reactions, a fission bomb obviously cannot be used to trigger the reaction. The difficulties of controlled fusion center on the containment of the nuclear fuel at the extremely high temperatures necessary for fusion for a time long enough to allow the reaction to take place. For deuterium-tritium fusion, this time is about 0.1 sec. At such temperatures the fuel is no longer in one of the ordinary states of matter but is instead a plasma , consisting of a mixture of electrons and charged atoms. Obviously, no solid container could hold such a hot mixture; therefore, containment attempts have been based on the electrical and magnetic properties of a plasma, using magnetic fields to form a "magnetic bottle." In 1994 U.S. researchers achieved a fusion reaction that lasted about a second and generated 10.7 million watts, using deuterium and tritium in a magnetically confined plasma. The use of tritium lowers the temperature required and increases the rate of the reaction, but it also increases the release of radioactive neutrons . Another method has used laser beams aimed at tiny pellets of fusion fuel.

If practical controlled fusion is achieved, it could have great advantages over fission as a source of energy. Deuterium is relatively easy to obtain, since it constitutes a small percentage of the hydrogen in water and can be separated by electrolysis, in contrast to the complex and expensive methods required to extract uranium-235 from its sources. In 2007 China, the European Union, India, Japan, Russia, South Korea, and the United States formally established the International Thermonuclear Experimental Reactor (ITER) Organization to build an experimental fusion reactor at Cadarache in S France that would use the "magnetic bottle" approach. The Lawrence Livermore National Laboratory's National Ignition Facility, based in Livermore, Calif., and dedicated in 2009, is exploring the use of high-energy lasers focused on hydrogen fuel to achieve nuclear fusion.

Bibliography

See H. Foreman, ed., Nuclear Power and the Public (1970); R. C. Lewis, Nuclear Power Rebellion: Citizen vs. the Atomic Industrial Establishment (1972); C. K. Ebinger, International Politics of Nuclear Energy (1978); S. Glasstone, Sourcebook on Atomic Energy (1979); G. S. Bauer and A. McDonald, ed., Nuclear Technologies in a Sustainable Energy System (1983); G. H. Clarfield and W. W. Wiecek, Nuclear America (1984).

Nuclear Energy

Nuclear energy, strictly conceived, has received rather scant attention within the literature of science and religion. However, if the focus is broadened to include nuclear technology—that is, nuclear energy and nuclear weapons considered together—then there is a modest increase in its treatment.

Benefits and risks

Nuclear energy has long been viewed as an alternative energy source to coal and petroleum, which are currently the principal sources of energy. Coal and petroleum provide efficient sources of energy, but their combustion also generates considerable carbon dioxide that escapes into the atmosphere. Although a few dissenters remain, the vast majority of climatologists hold that the build up of carbon dioxide in the atmosphere creates a greenhouse effect. This greenhouse effect dramatically warms the planet, which leads, in turn, to global climate change, resulting in different impacts on different regions of the planet.

Nuclear energy provides an especially attractive alternative to coal and petroleum because it does not contribute to the concentration of carbon dioxide in the atmosphere. Shifting to nuclear energy could potentially lead to a cleaner, healthier environment without a reduction in the human consumption of energy. However, the benefits of nuclear energy must be weighed against its substantial costs and risks. The principal cost of nuclear energy occurs with the safe disposal of radioactive wastes. In addition to the costs of disposal, there is the risk that nuclear radiation could be released into the environment, either at the nuclear power plant or at the site of waste disposal. Such a release could be accidental, the result of equipment malfunction or human error. There is also the risk of an intentional release of nuclear radiation as an act of terrorism. Whether accidental or intentional, such a release could potentially destroy all biotic life in the affected area and make the area sterile for life for the foreseeable future.

Although as of 2002 there have been no intentional releases of nuclear radiation into the environment, there have been two serious accidents at nuclear power plants. In 1979, there was an accident at the Three Mile Island nuclear power plant in Pennsylvania. There was another accident in 1986 at the Chernobyl nuclear power plant in Ukraine. Although very little nuclear radiation escaped from the Three Mile Island accident, nuclear radiation did escape from the Chernobyl accident, causing substantial ecological damage and the deaths of a number of people.

Theological perspectives

Within the science and religion literature, Ian Barbour provides one of the few focused treatments of nuclear energy in his book Ethics in an Age of Technology (1993). Barbour begins his examination with a discussion of risk. If risk is defined as the probability of an accident multiplied by the magnitude of its consequences, then the risk posed by nuclear energy is low, compared to other daily activities, such as driving a car. However, Barbour argues that evaluations of such technological risks must also be influenced by assumptions about human nature and social institutions. Taking a Christian religious perspective, Barbour argues that the individual and social sin inherent in the human condition calls for extreme caution in the development of nuclear energy because the risks and consequences are so high.

Shifting his focus to the safe disposal of radioactive wastes, Barbour identifies three ethical issues. First, Barbour notes that an issue of regional justice arises because radioactive waste disposal imposes extreme risks for a local population in order to provide a national benefit for everyone. Intergenerational justice raises a second ethical issue. The present generation would enjoy the benefits of nuclear energy, but passes on some of the burdens and risks of waste disposal to future generations. Finally, Barbour identifies the loss of public confidence in governments and the energy industry as a third ethical issue. His point here is that historically government and industry have been secretive and have failed to protect the public, rather than being transparent and promoting public discourse concerning the benefits, costs, and risks of nuclear energy. Barbour believes that more promising energy alternatives lie in energy conservation and in the use of other renewal energy sources, such as solar power.

In the 1980s, several religious writers warned that nuclear weapons and nuclear war threatened not only human life but the ecological viability of the planet. Two Christian theologians, Gordon Kaufman and Sallie McFague, argued further that these interconnected challenges were rooted in what has become a flawed understanding of God's power. In Theology for a Nuclear Age (1985), Kaufman argues that the threat of nuclear war and annihilation elicits two contrasting responses from traditional Christian conceptions of God. On the one hand, nuclear annihilation is interpreted in eschatological terms as God's action to bring the present age to an end. On the other hand, the threat of nuclear war is discounted because of the view that an almighty creator God, who loves humans and the rest of creation, would not allow such a disaster to occur. Kaufman notes that both responses have the effect of obscuring and undermining the responsibility that humans have for their actions. While the traditional understanding of God as omnipotent may have been appropriate for earlier times, Kaufman argues that this understanding is no longer appropriate in a nuclear age. In light of the threat of nuclear weapons, Kaufman proposes that Christian theologians need to reconceive of God's power, moving from a dualistic to an interdependent understanding. This would require theologians to rethink their formulation of the symbols "God" and "Christ." McFague concurs with Kaufman's analysis in her book Models of God: Theology for an Ecological, Nuclear Age (1987). As alternative models for thinking about God, McFague proposes mother, lover, and friend.

While both Kaufman and McFague were thinking initially of the threat of nuclear annihilation, they both extend their analyses to include ecological concerns. Thus, whether conceived broadly as nuclear technology, or more narrowly as nuclear energy, the literature of science and religion has consistently seen critical ecological implications for the planet.

See also Ecology; Ecology, Ethics of; Ecology, Religious and Philosophical Aspects; Ecology, Science of; Greenhouse Effect

Bibliography

barbour, ian. ethics in an age of technology. san francisco: harper, 1993.

kaufman, gordon d. theology for a nuclear age. manchester, uk: manchester university press, 1985.

mcfague, sallie. models of god: theology for an ecological, nuclear age. philadelphia: fortress press, 1987.

richard o. randolph

Energy, Nuclear

Nuclear energy is produced during reactions in the nucleus of an atom. Atoms can be thought of as miniature solar systems with the nucleus at the center like a sun and electrons orbiting around it like planets. Densely packed neutrons and protons make up the nucleus, which is held together with great force, the "strongest force in nature." When the nucleus is bombarded with a neutron, it can be split apart, a process called fission. Uranium is the heaviest natural element and has ninety-two protons. Because uranium atoms are so large, the atomic force that binds it together is relatively weak, so fission is more likely with uranium than other elements.

Fusion, another type of nuclear reaction, is the joining of atoms and can occur with elements of low atomic number, such as hydrogen, the lightest element, which has one proton. The first time physicists achieved fusion was in the 1950s with the hydrogen bomb. Fusion releases a tremendous amount of energy, but the energy is released so quickly and uncontrollably that fusion has not yet been harnessed as a usable source of energy.

Physicists formulated the principles of nuclear power in the early twentieth century. In 1939 German scientists discovered the process of nuclear fission, triggering a race with American scientists to use the massive energy release of fission to create a bomb. The atomic bomb was created by the United States in 1945; it was used to destroy Hiroshima and Nagasaki in Japan at the end of World War II.

After World War II, atomic power was seen as a potential new energy source. The U.S. government thought atomic explosions would be a laborsaving way to dig canals and reservoirs and to mine for gas and oil. As late as the 1960s, bombs were being set off above and below ground to test different ideas, resulting in radionuclide contamination of the soil that is still being addressed today.

A more successful use of atomic power was nuclear reactors that controlled the release of energy. Admiral Hyman G. Rickover guided the development of small reactors to power submarines, greatly extending their range and power. By the late 1950s, nuclear power was being developed for commercial electric power, initially in England. Morris, Illinois, was the site of the first U.S. commercial reactor. Nuclear weapons research was advanced by Russia and the United States during the Cold War, and a number of other countries, including China and India, have now developed nuclear weapons.

Nuclear Power Plants

Uranium is one of the least plentiful of minerals, making up only two parts per million (ppm) in the earth's crust. But because of its radioactivity, it is a plentiful supply of energy: one pound of uranium has as much energy as three million pounds of coal.

In 2002 there were 104 nuclear power reactors licensed to operate in the United States, and they accounted for 20 percent of the nation's electricity production and more than one-fourth of nuclear power capacity in the world. Many other countries, including France, Japan, and the United Kingdom, have nuclear power plants. Nuclear power accounts for about 80 percent of France's electrical power production.

How Nuclear Power Works

In nuclear power plants, neutrons collide with uranium atoms, splitting them. This split releases neutrons from the uranium that, in turn, collide with other atoms, causing a chain reaction. This chain reaction is regulated (or governed) by "control rods" that absorb neutrons. Fission releases energy that heats water to approximately 520°F in the core of the plant. The steam that is created is then used to spin turbines that are connected to generators, which produce electricity.

After the steam is used to power the turbine, it is cooled off and condensed into water. Some plants use water from rivers, lakes, or the ocean to cool the steam; returning this water to the environment can cause thermal pollution. Other plants use the hourglass-shaped cooling towers that are the familiar hallmark of many nuclear plants. For every unit of electricity produced by a nuclear power plant, about two units of wasted heat are sent into the environment.

Nuclear reactors are also used to power military submarines and surface ships. As in land-based reactors, nuclear-powered vessels use the heat produced by the chain reaction to make steam for a turbine. The turbine is connected to the propeller shafts aboard the ships rather than generators that produce electricity.

Radioactive Pollution from Nuclear Energy

By 1995 over 32,000 metric tons of highly radioactive waste had been produced by American nuclear reactors. That number is expected to rise to 75,000 metric tons by 2015.

Before the mid-1970s, the plan for fuel removed from nuclear reactors was to reprocess it and recycle the uranium into new fuel. Because a by-product of reprocessing is plutonium, a highly unstable element that can be used to make nuclear weapons, President Jimmy Carter ordered the end of reprocessing in 1977 due to security risks. Reprocessing also had a difficult time competing economically with the production of new uranium fuel.

Since then, the U.S. Department of Energy (DOE) has been studying storage sites for the long-term burial of such waste and is now focusing on Yucca Mountain in Nevada. The DOE has built a full-scale system of tunnels in the mountain at a cost of over $5 billion. Although the Yucca Mountain site is still controversial, there are no other sites presently under consideration.

Meanwhile, radioactive waste continues to be stored at the nuclear plants where it is produced. The most common option is to store it in a large steel-lined pool. As these pools fill up, fuel rods are stored in large steel and concrete casks.

see also Radioactive Fallout; Radioactive Waste; Thermal Pollution; Yucca Mountain.

Bibliography

mazuzan, george t., and walker, j. samuel. (1984). controlling the atom: the beginnings of nuclear regulation 1946–1962. berkeley: university of california press.

asimov, isaac. (1991). atom: journey across the subatomic cosmos. new york: truman talley books.

daley, michael j. (1997). nuclear power: promise or peril? minneapolis: lerner publications.

ramsey, charles b., and modarres, mohammad. (1998). commercial nuclear power: assuring safety for the future. new york: john wiley & sons.

internet resource

columbia college web site. "nuclear energy guide." available from http://www.spacekid.net/nuclear.

David Lochbaum

NUCLEAR POWER

Utilities Go Nuclear

In 1954 the government authorized private ownership of nuclear reactors as part of President Dwight D. Eisenhower's Atoms for Peace initiative, paving the way for utility companies to build nuclear power plants. By the mid 1960s many had "gone nuclear," though the cost of building reactors had proved far more than the early hopes that they could provide power for pennies a day. There was some public opposition to the plants—after all, most Americans' sole experience with the power of the atom was the devastating bombing of Hiroshima and Nagasaki in 1945. In California residents demanded the cancellation of the planned Bodega Bay reactor, sited on a geological fault, after an earthquake disrupted construction. Inhabitants of New York City resisted the siting of a plant in that densely populated area.

Energy Independence

Nevertheless, most people liked the idea of building atomic energy plants. The country was using increasing amounts of electric energy, and nuclear power promised to be cheaper and cleaner than burning fossil fuels, which created air pollution. Moreover, nuclear power had the aura of a neat, high-tech solution to complicated problems that people had come to expect from science and business. When an oil embargo by countries in the Middle East in 1973-1974 created shortages and high prices, atomic energy seemed to offer a way for the nation to achieve energy independence. Support for nuclear power was high, and its opponents were ridiculed. The antinuclear movement carried forward the traditions of the anti-Vietnam War movement and demonstrated against power plants, most visibly at the proposed site of Seabrook Station in New Hampshire, with what seemed ludicrously inadequate tools: sit-ins, civil disobedience, celebrity concerts, and rallies. To many, protesters' fear of radiation made them appear to be nature-loving cowards, and their opposition to nuclear power seemed to be vaguely un-American. One writer caricatured them as "vegetarians in leather jackets who drive imported cars to Seabrook listening to the Grateful Dead on their Japanese tape decks amid a marijuana haze."

Three Mile Island

At 4:00 A.M. on 28 March 1979 a mechanical failure of the cooling system at the Three Mile Island plant, near Harrisburg, Pennsylvania, was compounded by operator error. Technicians in the control room of the Unit 2 reactor, misunderstanding the nature of the problem, shut off all water to the reactor. With no water cooling it, the reactor became extremely hot—in excess of five thousand degrees—and began to melt. Within hours there was enough radiation in the containment dome to kill a person in minutes, and some radiation began leaking into the environment. It was another two days before the public learned how serious the accident was and officials began talking about a meltdown. Pregnant women and small children were evacuated. Ironically, the worst danger of a meltdown passed before the evacuation order was given—by then the reactor was underwater again. Nine days later the core had cooled sufficiently so that public officials felt safe in encouraging nearby residents to return to their homes; but the reactor was still hot even a year later.

MELTDOWN

A meltdown is the out-of-control melting of a superheated reactor core, which would become so hot that nothing could contain it. Experts differ on what would happen next. One early theory was that the core would fall through the earth and just keep going, "all the way to China." This scenario was later pushed aside, though not before it spawned a nuclear disaster movie starring Jane Fonda called The China Syndrome (1979). Now, some believe that it would simply wind up encased in volcanic glass about one hundred feet below the ground, sealed safely. Others disagree, suggesting that the breach of the containment dome would release fantastic amounts of radioactivity into the surrounding area, killing thousands, perhaps hundreds of thousands. One thing is clear: Unit 2 of the Three Mile Island nuclear power plant came perilously close to a full-scale disaster. The Presidential Commission report suggests that if the reactor had remained uncovered another twenty minutes, it would have melted down.

The Aftermath. While there were no apparent injuries at Three Mile Island, it dealt the nuclear power industry a blow that sent it sharply into decline. In April 1979 a Gallup poll found that 66 percent of the nation believed nuclear power to be unsafe. Although that number declined to 50 percent nine months later, the accident created an enduring pessimism about the industry. In 1980 environmental crusader Ralph Nader noted the changed climate of debate. "When I first began speaking against nuclear power," he said, "the audiences would ask me how I could prove that nuclear reactors were badly designed and poorly run. Now the audiences accept these problems without question and ask what alternatives we have to nuclear power."

RACE AND BIOLOGY

After fifteen years of civil rights struggle to assure black Americans of the full rights of citizenship and four decades of work by scientists to dismantle the notion of a biological basis for racial difference, Nobel Prize winning physicist William Shockley became a controversial figure in the 1970s when he argued that black Americans were genetically endowed with inferior intelligence. He was rebuffed by the National Academy of Sciences in 1970, when it refused to conduct a study along these lines. Shockley was increasingly unpopular on U.S. campuses by late 1973, when he was prevented from fulfilling speaking engagements by students who protested that he was a racist and a Fascist. In 1974 anthropologist Peggy Sanday offered a study many believed discredited Shockley's views, arguing that IQ differences were "exclusively a matter of environment."

Sources:

Carrol W. Pursell, Jr., ed., Technology in America: A History of Individuals and Ideas, second edition (Cambridge, Mass.: MIT Press, 1990);

Mark Stephens, Three Mile Island: The Hour-by-Hour Account of What Really Happened (New York: Random House, 1980).

Nuclear Power. In the aftermath of World War II and the beginning of the widely hailed “Atomic Age,” a plethora of books and articles suggested that the dangers of atomic weapons would be offset, at least partially, by the potential peaceful benefits of nuclear technology.Most of the projected applications, such as atomic automobiles and small reactors to heat and cool individual homes, were hopelessly fanciful. Proposals for building reactors to generate electricity in central power stations were more realistic, but progress was slow, especially with the Harry S. Truman administration's focus on the military uses of atomic energy.

In 1954, Congress passed a law intended to speed nuclear‐power development. The 1954 Atomic Energy Act made possible for the first time the wide commercial use of atomic energy by ending the government's monopoly of the technology. It assigned the Atomic Energy Commission (AEC) responsibility for both promoting nuclear power and regulating its safety. To the frustration of the AEC and the congressional Joint Committee on Atomic Energy, many utilities refrained from making a major commitment to nuclear power because of the abundance of conventional fuels and because of economic uncertainties and unresolved safety questions about the technology.

Beginning in the mid‐1960s, however, nuclear‐power development experienced a sudden and unanticipated boom. This came about for several reasons, including indications that large nuclear plants could compete economically with coal, the rise of interconnected electrical grids that encouraged the construction of large plants, and intensifying concern about air pollution from fossil‐fuel units. The nuclear boom not only produced a rapid growth in the number of nuclear plants but also in the size of individual plants, which in less than a decade grew from small demonstration facilities to behemoths.

The expansion of the nuclear industry took place at virtually the same time as the development of environmentalism as a potent political force. By the early 1970s, nuclear power had become a leading target of environmental activism and the subject of a highly visible and increasingly strident debate. Critics claimed that the technology was neither safe nor necessary; supporters argued that it was both safe and essential for the nation's energy future. At the center of the controversy were the unresolved issues of the likelihood and consequences of a major reactor accident and the effects of exposure to low levels of radiation. As the debate continued, public uneasiness about the risks of nuclear power increased substantially, and by the end of the 1970s orders for new plants has slowed dramatically. The slump in the industry resulted more from inflation and reduced demand for electricity than antinuclear activism, but the complaints of nuclear opponents strongly influenced public attitudes.

The debate over nuclear power intensified after the most serious accident in a U.S. nuclear power plant occurred at the Three Mile Island station near Harrisburg, Pennsylvania, in March 1979. The accident's severity was caused by mechanical failures and human error, and although only small amounts of radiation were released, the political fallout was heavy. The accident undermined the credibility of the Nuclear Regulatory Commission (NRC) and the nuclear industry while enhancing that of antinuclear critics.

After the shock of Three Mile Island, the NRC and the nuclear industry focused on a series of issues that had commanded only limited interest before the accident. These were intended to reduce the likelihood of another major accident, and, if one did occur, to enhance the ability of the NRC, the utility, and the public to cope with it. At the direction of the NRC, power companies improved plants that were operating or under construction. After a moratorium of more than one year, the NRC resumed issuing operating licenses for completed nuclear units in August 1980. By 1989, it had granted full‐power licenses to more than forty reactors, most of which had been under construction since the mid‐1970s. No new nuclear‐power reactors were ordered after 1978, and many earlier orders were canceled.

In 2000, 103 nuclear‐power plants were operating in the United States, providing about 20 percent of the nation's generating capacity. By that time, the debate over nuclear power had faded as a national issue, though it continued to trigger heated arguments in many local areas where plants were located.
See also Antinuclear Protest Movements; Electrical Industry; Electricity and Electrification; Hydroelectric Power; Nuclear Weapons.

Bibliography

George T. Mazuzan and and J. Samuel Walker , Controlling the Atom: The Beginnings of Nuclear Regulation, 1946–1962, 1984.
Joseph G. Morone and and Edward J. Woodhouse , The Demise of Nuclear Energy?, 1989.
Brian Balogh , Chain Reaction: Expert Debate and Public Participation in American Commercial Nuclear Power, 1945–1975, 1991.
J. Samuel Walker , Containing the Atom: Nuclear Regulation in a Changing Environment, 1963–1971, 1992.
Joseph V. Rees , Hostages of Each Other: The Transformation of Nuclear Safety since Three Mile Island, 1994.

J. Samuel Walker

NUCLEAR POWER

The use of nuclear power to generate electricity began in the late 1950s. At the close of the twentieth century, nuclear power was supplying about 20 percent of the electricity generated in the United States and about 16 percent worldwide.

Nuclear power has been the most controversial of all energy sources. Public concerns about reactor safety and environmental issues were especially heightened by the 1979 accident at Three Mile Island in Pennsylvania and the much more serious accident in 1986 at Chernobyl in Ukraine. Construction of new nuclear power plants has slowed considerably since then, and some industrialized countries may abandon this energy source. Concerns about disposal of spent nuclear fuel have also affected public confidence in nuclear power. Although many scientists believe that spent fuel and other highly radioactive wastes can be disposed of safely in a geologic repository located far below ground, disposal sites for these wastes have not been approved, and the need to store spent fuel until disposal facilities are available raises safety and environmental concerns. The public also has not supported development of new disposal facilities for low-level radioactive wastes generated at nuclear power plants and in many other commercial activities. Other factors contributing to public concerns have included environmental problems at sites operated under nuclear weapons programs and fears that plutonium produced at nuclear power plants could be diverted for use in nuclear weapons.

Public concerns about safety and environmental issues have been exacerbated by financial risks in the nuclear power industry, including the high cost of constructing and operating nuclear power plants, potentially high costs of decommissioning nuclear facilities, and costs for storage and disposal of spent fuel and other nuclear wastes. Nuclear power may not remain competitive with other energy sources unless these costs are reduced.

Proponents of nuclear power emphasize its significant benefits. Past accidents notwithstanding, the nuclear power industry has an enviable safety record in those industrialized countries that require extensive reactor safety systems. Uranium used in nuclear fuel is abundant, which reduces dependence on foreign energy supplies and preserves oil and natural gas for essential uses. Nuclear reactors produce the greatest amount of energy per amount of fuel of any nonrenewable energy source, and the environmental damage from use of nuclear power is less than with other major energy sources, especially coal. Perhaps most importantly, the use of nuclear power in place of coal, oil, and natural gas greatly reduces emissions of carbon dioxide, which is believed to be a factor in global warming, and other hazardous air pollutants.

Given these benefits, many energy experts believe that nuclear power is an important energy source for the future. A major challenge will be to address public concerns about safety and environmental issues. The keys to meeting this challenge may include resolving concerns about nuclear waste disposal, siting of new reactors in remote areas, developing smaller reactors that incorporate passive safety systems, and using standard power plant designs to lower construction and operating costs.

David C. Kocher

(see also: Chernobyl; Energy; Not In My Backyard [NIMBY]; Nuclear Waste; Risk Assessment, Risk Management; Three Mile Island )

Bibliography

Cohen, B. L. (1990). The Nuclear Energy Option: An Alternative for the 90s. New York: Plenum Press.

Gofman, J. W., and Tamplin, A. R. (1971). Poisoned Power: The Case Against Nuclear Power Plants. Emmaus, PA: Rodale Press.

Jungk, R. (1979). The New Tyranny: How Nuclear Power Enslaves Us. New York: Grosset & Dunlap, Inc.

Rhodes, R. (1993). Nuclear Renewal: Common Sense about Energy. New York: Whittle Books.

nuclear energy is obtained by releasing the binding energy which holds together atomic nuclei, for example, in uranium. This fission process was used in the development of the atomic bomb during the Second World War, but by the mid-1950s scientists had been able to control it within the reactor cores of experimental power stations to produce utilizable energy. The nuclear reactor releases energy in the form of heat which is used to generate steam, and the steam to generate electricity. Plutonium, a highly fissile material used in the manufacture of nuclear bombs, is a byproduct.

The Atomic Energy Authority oversaw the development of the nuclear industry, which from the outset proved controversial on strategic, cost, and environmental grounds. When in 1956 power was switched from the first generator at Calder Hall to the National Grid it was hailed as a great achievement but scant attention was paid to the real purpose of the programme, to breed plutonium for Britain's nuclear deterrent. An experimental fast reactor, built at Dounreay in the north of Scotland, began operation in 1959, and paved the way for the first fast-breeder reactor power station.

From the standpoint of the 1950s, discounting the perceived need for a nuclear deterrent during the Cold War, nuclear power seemed an excellent investment, given the likelihood that unit costs could be as little as a fifth that of fossil-fuel electricity. In the ensuing years the industry expanded, though the balance of cost advantage remained uncertain. But the upsurge of oil prices in the 1970s, coupled with uneasy labour relations in the coal-mines, added to the comparative economic attraction of nuclear power, which began to accelerate dramatically, as did the nuclear component of electricity output.

Successive British governments since the 1950s wanted to lessen dependence on petroleum-exporting countries, but with the development of North Sea oil and gas, this was less pressing. Energy requirements in general began to be adjusted as a response to the energy crisis, and this brought about a reassessment of the high-energy role of nuclear power. While in its early stages of development nuclear energy appeared environmentally inoffensive to the general public, increased concern was voiced about its safety following major disasters at power plants internationally during the 1980s, and about the twin problems of waste disposal and decommissioning of redundant plant.

Ian Donnachie

nuclear energy Energy released during a nuclear reaction as a result of the conversion of mass into energy according to Einstein's equation E = mc². The conversion involves the binding energy of the nucleus of an atom. Nuclear energy is released in two ways: by fission (splitting a heavy atomic nucleus in two) and by fusion (combining light aomic nuclei). Fission, discovered in 1938, is the process responsibile for the atomic bomb and for nuclear reactors in nuclear power stations that produce electricity. In 1942, German-born US physicist Enrico Fermi achieved the first sustained nuclear chain reaction. Fusion provides the energy for the stars and the hydrogen bomb. It also offers the prospect of cheap energy, once a method has been perfected for controlling fusion reactions. See also critical mass; Manhattan Project; nuclear weapon

nu·cle·ar pow·er • n. 1. electric or motive power generated by a nuclear reactor. 2. a country that has nuclear weapons. DERIVATIVES: nu·cle·ar-pow·ered adj.

nuclear power
1. a country that has nuclear weapons.

2. electric or motive power generated by a nuclear reactor.
nuclear-powered adj.

nuclear energy all forms of energy released in the course of nuclear fission or nuclear transformation.