Nuclear Power

Introduction

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

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

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

Historical Background and Scientific Foundations

What Is Nuclear Power?

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

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

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

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

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

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

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

WORDS TO KNOW

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

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

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

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

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

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

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

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

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

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

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

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

History of Nuclear Power Generation

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

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

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

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

Impacts and Issues

The Case for Nuclear Power

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

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

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

The Case against Nuclear Power

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

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

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

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

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

BIBLIOGRAPHY

Books

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

Periodicals

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

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

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

Web Sites

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

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

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

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

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

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

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

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

Larry Gilman