Nuclear power is a type of nuclear technology involving the controlled use of nuclear reactions to release energy for work, including propulsion, heat, and the generation of electricity. Nuclear energy is produced by a controlled nuclear chain reaction and creates heat—which is used to boil water, produce steam, and drive a steam turbine. The turbine can be used for mechanical work and also to generate electricity.
The use of nuclear power has also engendered much debate. Critics claim that nuclear power is a potentially dangerous energy source with a limited fuel supply (compared to renewable energy), and they note the problems of storing radioactive waste, the potential for radioactive contamination by accident or sabotage, and the possibility of nuclear proliferation. Advocates claim that these risks are small and can be further reduced by the technology in new reactors, and the safety record is good when compared to other major types of power plants. In addition, they note that many renewable energy technologies have not solved the problem of their intermittent power production.
As of 2004, nuclear power provided 6.5 percent of the world's energy and 15.7 percent of the world's electricity, with the U.S., France, and Japan together accounting for 57 percent of all nuclear generated electricity. As of 2007, the IAEA reported there are 435 nuclear power reactors in operation in the world, operating in 31 different countries. These provide about 17 percent of the world's electricity.
The United States produces the most nuclear energy, with nuclear power providing 20 percent of the electricity it consumes, while France produces the highest percentage of its electrical energy from nuclear reactors—80 percent as of 2006. In the European Union as a whole, nuclear energy provides 30 percent of the electricity. Nuclear energy policy differs between European Union countries, and some, such as Austria and Ireland, have no active nuclear power stations. In comparison, France has a large number of these plants, with 16 currently in use throughout the country.
Many military and some civilian (such as some icebreakers) ships use nuclear marine propulsion, a form of nuclear propulsion.
International research is ongoing into different safety improvements such as passively safe plants, the use of nuclear fusion, and additional uses of produced heat such as the hydrogen production (in support of a hydrogen economy), for desalinating sea water, and for use in district heating systems.
The first man-made reactor, Chicago Pile-1, achieved criticality on December 2, 1942, as part of the Manhattan Project.
Electricity was generated for the first time by a nuclear reactor on December 20, 1951, at the EBR-I experimental station near Arco, Idaho, which initially produced about 100 kW. The Arco Reactor was also the first to partially melt down (in 1955).
In 1952, a report by the Paley Commission (The President's Materials Policy Commission) for President Harry Truman made a "relatively pessimistic" assessment of nuclear power, and called for "aggressive research in the whole field of solar energy." A December 1953 speech by President Dwight Eisenhower, "Atoms for Peace," set the U.S. on a course of strong government support for the international use of nuclear power.
In 1954, Lewis Strauss, then chairman of the United States Atomic Energy Commission (forerunner of the U.S. Nuclear Regulatory Commission) famously spoke of electricity in the future being "too cheap to meter."  While few doubt he was thinking of atomic energy when he made the statement, he may have been referring to hydrogen fusion, rather than uranium fission. Actually, the consensus of government and business at the time was that nuclear (fission) power might eventually become merely economically competitive with conventional power sources.
On June 27 1954, the world's first nuclear power plant to generate electricity for a power grid started operations at Obninsk, USSR. The reactor produced 5 megawatts (electrical), enough to power 2,000 homes. In 1955 the United Nations' "First Geneva Conference," then the world's largest gathering of scientists and engineers, met to explore the technology. In 1957, EURATOM was launched alongside the European Economic Community (the latter is now the European Union). The same year also saw the launch of the International Atomic Energy Agency (IAEA).
The world's first commercial nuclear power station, Calder Hall in Sellafield, England was opened in 1956, with an initial capacity of 50 MW (later 200 MW). The Shippingport Reactor (Pennsylvania, 1957) was the first commercial nuclear generator to become operational in the United States.
One of the first organizations to develop utilitarian nuclear power was the U.S. Navy, for the purpose of propelling submarines and aircraft carriers. It has a good record in nuclear safety, perhaps because of the stringent demands of Admiral Hyman G. Rickover, who was the driving force behind nuclear marine propulsion. The U.S. Navy has operated more nuclear reactors than any other entity, including the Soviet Navy, with no publicly known major incidents. The first nuclear-powered submarine, USS Nautilus (SSN-571), put to sea in 1955. Two U.S. nuclear submarines, USS Scorpion and Thresher, have been lost at sea, though for reasons not related to their reactors, and their wrecks are situated such that the risk of nuclear pollution is considered low.
The 1973 oil crisis had a significant effect on the construction of nuclear power plants worldwide. The oil embargo led to a global economic recession, energy conservation, and high inflation that both reduced the projected demand for new electric generation capacity in the United States and made financing such capital intensive projects difficult. This contributed to the cancellation of over 100 reactor orders in the U.S. Even so, the plants already under construction effectively displaced oil for the generation of electricity. In 1973, oil generated 17 percent of the electricity in the United States. Today, oil is a minor source of electric power (except in Hawaii), while nuclear power now generates 20 percent of the country's electricity. The oil crisis caused other countries, such as France and Japan, which had relied even more heavily on oil for electric generation (39 percent and 73 percent respectively) to invest heavily in nuclear power. Today, nuclear power supplies about 80 percent and 30 percent of the electricity in those countries, respectively.
Installed nuclear capacity initially rose relatively quickly, rising from less than 1 gigawatt (GW) in 1960, to 100 GW in the late 1970s, and 300 GW in the late 1980s. Since the late 1980s capacity has risen much more slowly, reaching 366 GW in 2005, primarily due to Chinese expansion of nuclear power. Between around 1970 and 1990, more than 50 GW of capacity was under construction (peaking at over 150 GW in the late 70s and early 80s)—in 2005, around 25 GW of new capacity was planned. More than two-thirds of all nuclear plants ordered after January 1970 were eventually canceled.
During the 1970s and 1980s rising economic costs (related to vastly extended construction times largely due to regulatory changes and pressure-group litigation) and falling fossil fuel prices made nuclear power plants then under construction less attractive. In the 1980s (U.S.) and 1990s (Europe), flat load growth and electricity liberalization also made the addition of large new baseload capacity unattractive.
A general movement against nuclear power arose during the last third of the twentieth century, based on the fear of a possible nuclear accident and on fears of radiation, as well as in opposition to nuclear waste production, transport, and final storage. Perceived risks on the citizens' health and safety, the 1979 accident at Three Mile Island, and the 1986 Chernobyl disaster played a part in stopping new plant construction in many countries. However, in the U.S. new construction dropped sharply before the Three Mile Island accident, after the 1973 oil crises. and the Brookings Institution suggests that new nuclear units have not been ordered in the U.S. primarily for economic reasons rather than fears of accidents.
Unlike the Three Mile Island accident, the much more serious Chernobyl accident did not increase regulations affecting Western reactors, since the Chernobyl reactors were of the problematic RBMK design only used in the Soviet Union, lacking, for example, containment buildings. An international organization to promote safety awareness and professional development on operators in nuclear facilities was created: WANO; World Association of Nuclear Operators.
As of March 1, 2007, Watts Bar 1, which came on-line in 1997, was the last U.S. commercial nuclear reactor to go on-line. This is often quoted as evidence of a successful worldwide campaign for nuclear power phase-out. However, political resistance to nuclear power has only ever been successful in parts of Europe, in New Zealand, in the Philippines, and in the United States. Even in the U.S. and throughout Europe, investment in research and in the nuclear fuel cycle has continued, and some experts predict that electricity shortages, fossil fuel price increases, global warming from fossil fuel use, new technology such as passively safe plants, and national energy security will renew the demand for nuclear power plants.
Many countries remain active in developing nuclear power, including Japan, China, and India, all actively developing both fast and thermal technology, South Korea and the United States, developing thermal technology only, and South Africa and China, developing versions of the Pebble Bed Modular Reactor (PBMR). Finland and France actively pursue nuclear programs; Finland has a new European Pressurized Reactor under construction by Areva. Japan has an active nuclear construction program with new units brought on-line in 2005. In the U.S., three consortia responded in 2004 to the U.S. Department of Energy's solicitation under the Nuclear Power 2010 Program and were awarded matching funds—the Energy Policy Act of 2005 authorized subsidies for up to six new reactors, and authorized the Department of Energy to build a reactor based on the Generation IV Very-High-Temperature Reactor concept to produce both electricity and hydrogen. As of the early twenty first century, nuclear power is of particular interest to both China and India to serve their rapidly growing economies—both are developing fast breeder reactors. See also future energy development. In the energy policy of the United Kingdom, it is recognized that there is a likely future energy supply shortfall, which may have to be filled by either new nuclear plant construction or maintaining existing plants beyond their programmed lifetime.
On September 22, 2005, it was announced that two sites in the U.S. had been selected to receive new power reactors (exclusive of the new power reactor scheduled for INL).
Conventional thermal power plants all have a fuel source to provide heat. Examples are gas, coal, or oil. For a nuclear power plant, this heat is provided by nuclear fission inside the nuclear reactor. When a relatively large fissile atomic nucleus (usually uranium-235 or plutonium-239) is struck by a neutron, it forms two or more smaller nuclei as fission products, releasing energy and neutrons in a process called nuclear fission. The neutrons then trigger further fission. And so on. When this nuclear chain reaction is controlled, the energy released can be used to heat water, produce steam, and drive a turbine that generates electricity. It should be noted that a nuclear explosive involves an uncontrolled chain reaction, and the rate of fission in a reactor is not capable of reaching sufficient levels to trigger a nuclear explosion because commercial reactor grade nuclear fuel is not enriched to a high enough level.
The chain reaction is controlled through the use of materials that absorb and moderate neutrons. In uranium-fueled reactors, neutrons must be moderated (slowed down) because slow neutrons are more likely to cause fission when colliding with a uranium-235 nucleus. Light water reactors use ordinary water to moderate and cool the reactors. When at operating temperatures if the temperature of the water increases, its density drops, and fewer neutrons passing through it are slowed enough to trigger further reactions. That negative feedback stabilizes the reaction rate.
A number of other designs for nuclear power generation, the Generation IV reactors, are the subject of active research and may be used for practical power generation in the future. A number of the advanced nuclear reactor designs could also make critical fission reactors much cleaner, much safer, and/or much less of a risk to the proliferation of nuclear weapons.
Controlled nuclear fusion could in principle be used in fusion power plants to produce power without the complexities of handling actinides, but significant scientific and technical obstacles remain. Several fusion reactors have been built, but as yet none has "produced" more thermal energy than electrical energy consumed. Despite research having started in the 1950s, no commercial fusion reactor is expected before 2050. The ITER project is currently leading the effort to commercialize fusion power.
The topic of nuclear safety covers:
Nuclear economics has become increasingly controversial, since multi-billion dollar investments ride on the choice of an energy source. Which power source (generally coal, natural gas, nuclear, or wind) is most cost-effective depends on given assumptions used in a particular study.
A nuclear reactor is only part of the life-cycle for nuclear power. The process starts with mining. Generally, uranium mines are either open-pit strip mines, or in-situ leach mines. In either case, the uranium ore is extracted, usually converted into a stable and compact form, such as yellowcake, and then transported to a processing facility. Here, the yellowcake is converted to uranium hexafluoride, which is then enriched using various techniques. At this point, the enriched uranium, containing more than the natural 0.7 percent U-235, is used to make rods of the proper composition and geometry for the particular reactor that the fuel is destined for. The fuel rods will spend about 3 years inside the reactor, generally, until about 3 percent of their uranium has been fissioned, then they will be moved to a spent fuel pool, where the short lived isotopes generated by fission can decay away. After about 5 years in a cooling pond, the spent fuel is radioactively cool enough to handle, and it can be moved to dry storage casks or reprocessed.
Uranium is a common element, approximately as common as tin or zinc, and it is a constituent of most rocks, as well as of the sea. The world's present measured resources of uranium, economically recoverable at a price of 130 $/kg, are enough to last for some 70 years at current consumption. This represents a higher level of assured resources than is normal for most minerals. On the basis of analogies with other metal minerals, a doubling of price from present levels could be expected to create about a tenfold increase in measured resources, over time. The fuel's contribution to the overall cost of the electricity produced is relatively small, so even a large fuel price escalation will have relatively little effect on final price. For instance, typically a doubling of the uranium market price would increase the fuel cost for a light water reactor by 26 percent and the electricity cost about 7 percent (whereas doubling the gas price would typically add 70 percent to the price of electricity from that source). At higher prices, eventually extraction from sources such as granite and seawater become economically feasible. Current light water reactors make relatively inefficient use of nuclear fuel, leading to energy waste. But nuclear reprocessing makes this waste reusable (except in the U.S., where this is not allowed) and more efficient reactor designs would allow better use of the available resources (and reduce the amount of waste material).
As opposed to current light water reactors which use uranium-235 (0.7 percent of all natural uranium), fast breeder reactors use uranium-238 (99.3 percent of all natural uranium). It has been estimated that there is up to five-billion years’ (also the estimated remaining life of the Sun) worth of uranium-238 for use in these power plants. Breeder technology has been used in several reactors, but requires higher uranium prices before becoming justified economically. As of December 2005, the only breeder reactor producing power is BN-600 in Beloyarsk, Russia. (The electricity output of BN-600 is 600 MW——ussia has planned to build another unit, BN-800, at Beloyarsk nuclear power plant.) Also, Japan's Monju reactor is planned for restart (having been shut down since 1995), and both China and India intend to build breeder reactors.
Another alternative would be to use uranium-233 bred from thorium as fission fuel—the thorium fuel cycle. Thorium is three times more abundant in the Earth's crust than uranium, and (theoretically) all of it can be used for breeding, making the potential thorium resource orders of magnitude larger than the uranium fuel cycle operated without breeding. Unlike the breeding of U-238 into plutonium, fast breeder reactors are not necessary—it can be performed satisfactorily in more conventional plants.
Fusion power commonly proposes the use of deuterium, an isotope of hydrogen, as fuel and in many current designs also lithium. Assuming a fusion energy output equal to the current global output and that this does not increase in the future, then the known current lithium reserves would last 3000 years, lithium from sea water would last 60 million years, and a more complicated fusion process using only deuterium from sea water would have fuel for 150 billion years.
Uranium enrichment produces many tons of depleted uranium (DU) which consists of U-238, with most of the easily fissile U-235 isotope removed. U-238 is a tough metal with several commercial uses—for example, aircraft production, radiation shielding, and making bullets and armor—as it has a higher density than lead. There are concerns that U-238 may lead to health problems in groups exposed to this material excessively, like tank crews and civilians living in areas where large quantities of DU ammunition have been used.
The safe storage and disposal of nuclear waste is a significant challenge. The most important waste stream from nuclear power plants is spent fuel. A large nuclear reactor produces 3 cubic meters (25-30 metric tons) of spent fuel each year. It is primarily composed of unconverted uranium as well as significant quantities of transuranic actinides (plutonium and curium, mostly). In addition, about 3 percent of it is made of fission products. The actinides (uranium, plutonium, and curium) are responsible for the bulk of the long term radioactivity, whereas the fission products are responsible for the bulk of the short term radioactivity.
Spent fuel is highly radioactive and needs to be handled with great care and forethought. However, spent nuclear fuel becomes less radioactive over time. After 40 years, the radiation flux is 99.9 percent lower than it was the moment the spent fuel was removed, although still dangerously radioactive.
Spent fuel rods are stored in shielded basins of water (spent fuel pools), usually located on-site. The water provides both cooling for the still-decaying uranium, and shielding from the continuing radioactivity. After a few decades some on-site storage involves moving the now cooler, less radioactive fuel to a dry-storage facility or dry cask storage, where the fuel is stored in steel and concrete containers until its radioactivity decreases naturally ("decays") to levels safe enough for other processing. This interim stage spans years or decades, depending on the type of fuel. Most U.S. waste is currently stored in temporary storage sites requiring oversight, while suitable permanent disposal methods are discussed.
As of 2003, the United States had accumulated about 49,000 metric tons of spent nuclear fuel from nuclear reactors. Underground storage at Yucca Mountain in the U.S. has been proposed as permanent storage. After 10,000 years of radioactive decay, according to United States Environmental Protection Agency standards, the spent nuclear fuel will no longer pose a threat to public health and safety.
The amount of waste can be reduced in several ways, particularly reprocessing. Even so, the remaining waste will be substantially radioactive for at least 300 years even if the actinides are removed, and for up to thousands of years if the actinides are left in. Even with separation of all actinides, and using fast breeder reactors to destroy by transmutation some of the longer-lived non-actinides as well, the waste must be segregated from the environment for one to a few hundred years, and therefore this is properly categorized as a long-term problem. Subcritical reactors or fusion reactors could also reduce the time the waste has to be stored. It has been argued that the best solution for the nuclear waste is above ground temporary storage since technology is rapidly changing. The current waste may well become a valuable resource in the future.
The nuclear industry also produces a volume of low-level radioactive waste in the form of contaminated items like clothing, hand tools, water purifier resins, and (upon decommissioning) the materials of which the reactor itself is built. In the United States, the Nuclear Regulatory Commission has repeatedly attempted to allow low-level materials to be handled as normal waste: Landfilled, recycled into consumer items, and so forth. Most low-level waste releases very low levels of radioactivity and is only considered radioactive waste because of its history. For example, according to the standards of the NRC, the radiation released by coffee is enough to treat it as low level waste.
In countries with nuclear power, radioactive wastes comprise less than 1 percent of total industrial toxic wastes, which remain hazardous indefinitely unless they decompose or are treated so that they are less toxic or, ideally, completely non-toxic. Overall, nuclear power produces far less waste material than fossil-fuel based power plants. Coal-burning plants are particularly noted for producing large amounts of toxic and mildly radioactive ash due to concentrating naturally occurring metals and radioactive material from the coal. Contrary to popular belief, coal power actually results in more radioactive waste being released into the environment than nuclear power .
Reprocessing can potentially recover up to 95 percent of the remaining uranium and plutonium in spent nuclear fuel, putting it into new mixed oxide fuel. This would produce a reduction in long term radioactivity within the remaining waste, since this is largely short-lived fission products, and reduces its volume by over 90 percent. Reprocessing of civilian fuel from power reactors is currently done on a large scale in Britain, France and (formerly) Russia, will be done in China and perhaps India, and is being done on an expanding scale in Japan. The potential of reprocessing has not been achieved because it requires breeder reactors, which are not yet commercially available. France is generally cited as the most successful reprocessor, but it presently only recycles 28 percent (by weight) of the yearly fuel use, 7 percent within France and another 21 percent in Russia.
Unlike other countries, the U.S. has stopped civilian reprocessing as one part of U.S. non-proliferation policy, since reprocessed material such as plutonium can be used in nuclear weapons. Spent fuel is all currently treated as waste. In February 2006, a new U.S. initiative, the Global Nuclear Energy Partnership, was announced. It would be an international effort to reprocess fuel in a manner making nuclear proliferation unfeasible, while making nuclear power available to developing countries.
Critics, including most major environmental groups, claim that nuclear power is an uneconomic and potentially dangerous energy source with a limited fuel supply, especially compared to renewable energy, and dispute whether the costs and risks can be reduced through new technology. They also point to the problem of storing radioactive waste, the potential for possibly severe radioactive contamination by accident or sabotage, and the possibility of nuclear proliferation. Proponents claim that these risks are small and can be further reduced by the technology in the new reactors. They further claim that the safety record is already good when compared to the other major kinds of power plants, that many renewables have not solved the problem with their intermittent power production, in effect limiting them to a minority share of power production, and that nuclear power is a sustainable energy source.
The International Nuclear Event Scale (INES), developed by the International Atomic Energy Agency (IAEA), is used to communicate the severity of nuclear accidents on a scale of 0 to 7. The two most well known events are the Three Mile Island accident and the Chernobyl disaster.
The 1979 accident at Three Mile Island Unit 2 was the worst civilian nuclear accident outside the Soviet Union (INES score of 5). The reactor experienced a partial core meltdown. However, the reactor vessel and containment building were not breached and little radiation was released to the environment (well below natural background radiation levels). The event resulted in fundamental changes in how plants in the West were to be maintained and operated. There were no immediate fatalities or injuries stemming from the event and, although debated by some groups, the mainstream view is that no member of the public was injured and no detectable increase in the incidence of cancer is expected.
The Chernobyl disaster in 1986 at the Chernobyl Nuclear Power Plant in the Ukrainian Soviet Socialist Republic (now Ukraine) was the worst nuclear accident in history and is the only event to receive an INES score of 7. The power excursion and resulting steam explosion and fire spread radioactive contamination across large portions of Europe. Eight workers were fatally irradiated, and the death toll among civilians may be as high as 4000. Operator error and plant design were cited as causes for the explosion.
Design changes are being pursued to lessen the risks of fission reactors; in particular, passively safe plants (such as the ESBWR) are available to be built and inherently safe designs are being pursued. Fusion reactors which may come to exist in the future theoretically have very little risk.
The World Nuclear Association provides a comparison of deaths due to major accidents among different forms of energy production. In their comparison, deaths per TWy of electricity produced are 885 for hydropower, 342 for coal, 85 for natural gas, and 8 for nuclear. Not included in the study are deaths due to black lung disease or air pollution from fossil fuels.
Nuclear power plants are generally (although not always) considered "hard" targets. In the U.S., plants are surrounded by a double row of tall fences which are electronically monitored. The plant grounds are patrolled by a sizable force of armed guards. The NRC's "Design Basis Threat" criteria for plants is a secret, and so what size attacking force the plants are able to protect against is unknown. However, to Scram a plant takes less than 5 seconds while unimpeded restart takes hours, severely hampering a terrorist force whose goal is to release radioactivity.
Attack from the air is a more problematic concern. The most important barrier against the release of radioactivity in the event of an aircraft strike is the containment building and its missile shield. The NRC's Chairman has said "Nuclear power plants are inherently robust structures that our studies show provide adequate protection in a hypothetical attack by an airplane. The NRC has also taken actions that require nuclear power plant operators to be able to manage large fires or explosions—no matter what has caused them." 
In addition, supporters point to large studies carried out by NRC and other agencies that tested the robustness of both reactor and waste fuel storage, and found that they should be able to sustain a terrorist attack comparable to the September 11 terrorist attacks in the U.S. Spent fuel is usually housed inside the plant's "protected zone" or a spent nuclear fuel shipping cask; stealing it for use in a "dirty bomb" is extremely difficult. Exposure to the intense radiation would almost certainly quickly incapacitate or kill any terrorists who attempt to do so. Nuclear power plants are designed to withstand threats deemed credible at the time of licensing. However, as weapons evolve it cannot be said unequivocally that within the 60 year life of a plant it will not become vulnerable. In addition, the future status of storage sites may be in doubt. Other forms of energy production are also vulnerable to attack, such as hydroelectric dams and LNG tankers.
Opponents of nuclear power express concerns that nuclear waste is not well protected, and that it could potentially be used as a terrorist weapon, as a dirty bomb, quoting a 1999 Russian incident where workers were caught trying to sell 5 grams of radioactive material on the open market, or the incident in 1993, where Russian workers were caught selling 4.5 kilograms of enriched uranium. The UN has since called upon world leaders to improve security in order to prevent radioactive material falling into the hands of terrorists. Proponents of nuclear power argue, however, that a dirty bomb is not a very effective weapon and would cause relatively few casualties, although the psychological impact would be high.
Most of human exposure to radiation comes from natural background radiation. Most of the remaining exposure comes from medical procedures. Several large studies in the U.S., Canada, and Europe have found no evidence of any increase in cancer mortality among people living near nuclear facilities. For example, in 1990, the National Cancer Institute (NCI) of the National Institutes of Health announced that a large-scale study, which evaluated mortality from 16 types of cancer, found no increased incidence of cancer mortality for people living near 62 nuclear installations in the United States. The study showed no increase in the incidence of childhood leukemia mortality in the study of surrounding counties after start-up of the nuclear facilities. The NCI study, the broadest of its kind ever conducted, surveyed 900,000 cancer deaths in counties near nuclear facilities.
However, in Britain there are elevated childhood leukemia levels near some industrial facilities, particularly near Sellafield, where children living locally are ten times more likely to contract the cancer. The reasons for these increases, or clusters, are unclear, but one study of those near Sellafield has ruled out any contribution from nuclear sources. Apart from anything else, the levels of radiation at these sites are orders of magnitude too low to account for the excess incidences reported. One explanation is viruses or other infectious agents being introduced into a local community by the mass movement of migrant workers. Likewise, small studies have been conducted in Germany and France, and have found an increased incidence of childhood leukemia near some nuclear power plants. Nonetheless, the results of larger multi-site studies in these countries invalidate the hypothesis of an increased risk of leukemia related to nuclear discharge. The methodology and very small samples in the studies finding an increased incidence have been criticized. Also, one study focusing on Leukemia clusters in industrial towns in England indicated a link to high-capacity electricity lines suggesting that the production or distribution of the electricity, rather than the nuclear reaction, may be a factor.
Nuclear proliferation is the spread of nuclear weapons and related technology to nations not recognized as "Nuclear Weapon States" by the Nuclear Nonproliferation Treaty. Opponents of civilian nuclear power point out that nuclear technology may be a dual-use technology, and some of the materials and knowledge used in a civilian nuclear program may be used to develop nuclear weapons.
Original impetus for development of nuclear power came from the military nuclear programs, including the early designs of power reactors that were developed for nuclear submarines. In many countries governmental and civilian nuclear programs are linked, at least by common research projects and through agencies such as the U.S. DOE. In the U.S., for example, the first goal of the Department of Energy is "to advance the national, economic, and energy security of the United States; to promote scientific and technological innovation in support of that mission; and to ensure the environmental cleanup of the national nuclear weapons complex."
To prevent weapons proliferation, safeguards on nuclear technology were published in the Nuclear Non-Proliferation Treaty (NPT) and monitored since 1968 by the International Atomic Energy Agency (IAEA). Nations signing the treaty are required to report to the IAEA what nuclear materials they hold and their location. They agree to accept visits by IAEA auditors and inspectors to verify independently their material reports and physically inspect the nuclear materials concerned to confirm physical inventories of them in exchange for access to nuclear materials and equipment on the global market.
Several states did not sign the treaty and were able to use international nuclear technology (often procured for civilian purposes) to develop nuclear weapons (India, Pakistan, Israel, and South Africa). Of those who have signed the treaty and received shipments of nuclear paraphernalia, many states have either claimed to, or been accused of, attempting to use supposedly civilian nuclear power plants for developing weapons. Certain types of reactors may be more conducive to producing nuclear weapons materials than others, such as possible future fast breeder reactors, and a number of international disputes over proliferation have centered on the specific model of reactor being contracted for in a country suspected of nuclear weapon ambitions.
There is concern in some countries over North Korea and Iran operating research reactors and fuel enrichment plants, since those countries refuse adequate IAEA oversight and are believed to be trying to develop nuclear weapons. North Korea admits that it is developing nuclear weapons, while the Iranian government vehemently denies such claims. Some proponents of nuclear power agree that the risk of nuclear proliferation may be a reason to prevent nondemocratic developing nations from gaining any nuclear technology but argue that this is no reason for democratic developed nations to abandon their nuclear power plants, especially in the light of the democratic peace theory, which argues that democracies refrain from war against each other. There is, however, always the risk that information of new technologies will be stolen and made public (for example, on the internet), making it ever easier for any country to build its own nuclear facilities. However, all power sources and technology can be used to produce and use weapons. The weapons of mass destruction used in chemical warfare and biological warfare are not dependent on nuclear power. Humans could still make war even if all technology was forbidden.
Proponents also note that nuclear power, like some other power sources, provides steady energy at a consistent price without competing for energy resources from other countries, something that may contribute to wars.
Russia has begun building the world’s first floating nuclear power plant. The £100 million vessel, the Lomonosov, to be completed in 2010, is the first of seven plants that Moscow says will bring vital energy resources to remote Russian regions. While producing only a small fraction of the power of a standard Russian land-based plant, it can supply power to a city of 200,000, or function as a desalination plant. The Russian atomic energy agency said that at least 12 countries were also interested in buying floating nuclear plants. 
Environmental groups and nuclear experts are concerned that floating nuclear plants will be more vulnerable to accidents and terrorism than land-based stations. They point to a history of naval and nuclear accidents in Russia and the former Soviet Union, including the Chernobyl disaster of 1986. Russia does have 50 years of experience operating a fleet of nuclear powered icebreakers that are also used for scientific and Arctic tourism expeditions. The Russians have commented that a nuclear reactor that sinks, such as the similar reactor involved in the Kursk explosion, can be raised and probably put back into operation. At this time it is not known what, if any, containment structure or associated missile shield will be built on the ship. The Russians believe that an airliner striking the ship would not destroy the reactor.
Nuclear generation does not directly produce sulfur dioxide, nitrogen oxides, mercury, or other pollutants associated with the combustion of fossil fuels (pollution from fossil fuels is blamed for many deaths each year in the U.S. alone). It also does not directly produce carbon dioxide, which has led some environmentalists to advocate increased reliance on nuclear energy as a means to reduce greenhouse gas emissions (which contribute to global warming). Non-radioactive water vapor is the significant operating emission from nuclear power plants.
According to a 2007 story broadcast on 60 Minutes, nuclear power gives France the cleanest air of any industrialized country, and the cheapest electricity in all of Europe.
Like any power source (including renewables like wind and solar energy), the facilities to produce and distribute the electricity require energy to build and subsequently decommission. Mineral ores must be collected and processed to produce nuclear fuel. These processes are either directly powered by diesel and gasoline engines, or draw electricity from the power grid, which may be generated from fossil fuels. Life cycle analyses assess the amount of energy consumed by these processes (given today's mix of energy resources) and calculate, over the lifetime of a nuclear power plant, the amount of carbon dioxide saved (related to the amount of electricity produced by the plant) vs. the amount of carbon dioxide used (related to construction and fuel acquisition).
In a study conducted in 2006 by the UK's Parliamentary Office of Science and Technology (POST), nuclear power's lifecycle was evaluated to emit the least amount of carbon dioxide (very close to wind power's lifecycle emissions) when compared to the other alternatives (fossil oil, coal, and some renewable energy including biomass and PV solar panels).  In 2006, a UK government advisory panel, The Sustainable Development Commission, concluded that if the UK's existing nuclear capacity were doubled, it would provide an 8 percent decrease in total UK CO2 emissions by 2035. This can be compared to the country's goal to reduce greenhouse gas emissions by 60 percent by 2050. On September 21, 2005, the Oxford Research Group published a report, in the form of a memorandum to a committee of the British House of Commons, which argued that, while nuclear plants do not generate carbon dioxide while they operate, the other steps necessary to produce nuclear power, including the mining of uranium and the storing of waste, result in substantial amounts of carbon dioxide pollution.
According to one life cycle study from 2001–2005, carbon dioxide emissions from nuclear power per kilowatt hour could range from 20 percent to 120 percent of those for natural gas-fired power stations depending on the availability of high grade ores. The study was strongly criticized by the World Nuclear Association (WNA), rebutted in 2003, then dismissed by the WNA in 2006, based on its own life-cycle-energy calculation (with comparisons). The WNA also listed several other independent life cycle analyses which show similar emissions per kilowatt-hour from nuclear power and from renewables such as wind power.
|Nuclear engineering||Nuclear physics | Nuclear fission | Nuclear fusion | Radiation | Ionizing radiation | Atomic nucleus | Nuclear reactor | Nuclear safety|
|Nuclear material||Nuclear fuel | Fertile material | Thorium | Uranium | Enriched uranium | Depleted uranium | Plutonium|
|Nuclear power||Nuclear power plant | Radioactive waste | Fusion power | Future energy development | Inertial fusion power plant | Pressurized water reactor | Boiling water reactor | Generation IV reactor | Fast breeder reactor | Fast neutron reactor | Magnox reactor | Advanced gas-cooled reactor | Gas-cooled fast reactor | Molten salt reactor | Liquid-metal-cooled reactor | Lead-cooled fast reactor | Sodium-cooled fast reactor | Supercritical water reactor | Very high temperature reactor | Pebble bed reactor | Integral Fast Reactor | Nuclear propulsion | Nuclear thermal rocket | Radioisotope thermoelectric generator|
|Nuclear medicine||PET | Radiation therapy | Tomotherapy | Proton therapy | Brachytherapy|
|Nuclear weapons||History of nuclear weapons | Nuclear warfare | Nuclear arms race | Nuclear weapon design | Effects of nuclear explosions | Nuclear testing | Nuclear delivery | Nuclear proliferation | List of states with nuclear weapons | List of nuclear tests|
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