nuclear power

The Ikata Nuclear Power Plant, a pressurized water reactor that cools by secondary coolant exchange with the ocean.

The Susquehanna Steam Electric Station, a boiling water reactor. The reactors are located inside the rectangular containment buildings towards the front of the cooling towers.

Three nuclear powered ships, (top to bottom) nuclear cruisers USS Bainbridge and USS Long Beach with USS Enterprise the first nuclear powered aircraft carrier in 1964. Crew members are spelling out Einstein's mass-energy equivalence formula E=mc² on the flight deck.

Nuclear power is power (generally electrical) produced from controlled (ie, non-explosive) nuclear reactions. Commercial plants in use to date use nuclear fission reactions. Electric utility reactors heat water to produce steam, which is then used to generate electricity. In 2007, 14% of the world's electricity came from nuclear power, despite concerns about safety and radioactive waste management. More than 150 naval vessels using nuclear propulsion have been built.

Nuclear fusion reactions are widely believed to be safer than fission and appear potentially viable, though technically quite difficult. Fusion power has been under intense theoretical and experimental investigation for many years.

Both fission and fusion appear promising for some space propulsion applications in the mid- to distant-future, using low thrust for long durations to achieve high mission velocities. Radioactive decay has been used on a relatively small (few kW) scale, mostly to power space missions and experiments.

Use

Historical and projected world energy use by energy source, 1980-2030, Source: International Energy Outlook 2007, EIA.

Nuclear power installed capacity and generation, 1980 to 2007 (EIA).

The status of nuclear power globally. Click image for legend.

As of 2005, nuclear power provided 2.1% of the world's energy and 15% of the world's electricity, with the U.S., France, and Japan together accounting for 56.5% of nuclear generated electricity.^[1] In 2007, the IAEA reported there were 439 nuclear power reactors in operation in the world,^[2] operating in 31 countries.^[3]

In 2007, nuclear power's share of global electricity generation dropped to 14%. According to the International Atomic Energy Agency, the main reason for this was an earthquake in western Japan on 16 July 2007, which shut down all seven reactors at the Kashiwazaki-Kariwa Nuclear Power Plant. There were also several other reductions and "unusual outages" experienced in Korea and Germany. Also, increases in the load factor for the current fleet of reactors appear to have plateaued.^[4]

The United States produces the most nuclear energy, with nuclear power providing 19%^[5] of the electricity it consumes, while France produces the highest percentage of its electrical energy from nuclear reactors—78% as of 2006.^[6] In the European Union as a whole, nuclear energy provides 30% of the electricity.^[7] Nuclear energy policy differs between European Union countries, and some, such as Austria, Estonia, and Ireland, have no active nuclear power stations. In comparison, France has a large number of these plants, with 16 multi-unit stations in current use.

In the US, while the Coal and Gas Electricity industry is projected to be worth $85 billion by 2013, Nuclear Power generators are forecast to be worth $18 billion.^[8]

Many military and some civilian (such as some icebreaker) ships use nuclear marine propulsion, a form of nuclear propulsion.^[9] A few space vehicles have been launched using full-fledged nuclear reactors: the Soviet RORSAT series and the American SNAP-10A.

International research is continuing into safety improvements such as passively safe plants,^[10] the use of nuclear fusion, and additional uses of process heat such as hydrogen production (in support of a hydrogen economy), for desalinating sea water, and for use in district heating systems.

History

Origins

As the father of nuclear physics, Ernest Rutherford is credited with splitting the atom in 1917.^[11] His team in England bombarded nitrogen with naturally occurring alpha particles from radioactive material and observed a proton emitted with energy higher than the alpha particle. In 1932 two of his students John Cockcroft and Ernest Walton, working under Rutherford's direction, attempted to split the atomic nucleus by entirely artificial means, using a particle accelerator to bombard lithium with protons, thereby producing two helium nuclei.^[12]

After James Chadwick discovered the neutron in 1932, nuclear fission was first experimentally achieved by Enrico Fermi in 1934 in Rome, when his team bombarded uranium with neutrons.^[13] In 1938, German chemists Otto Hahn^[14] and Fritz Strassmann, along with Austrian physicists Lise Meitner^[15] and Meitner's nephew, Otto Robert Frisch,^[16] conducted experiments with the products of neutron-bombarded uranium. They determined that the relatively tiny neutron split the nucleus of the massive uranium atoms into two roughly equal pieces, which was a surprising result. Numerous scientists, including Leo Szilard who was one of the first, recognized that if fission reactions released additional neutrons, a self-sustaining nuclear chain reaction could result. This spurred scientists in many countries (including the United States, the United Kingdom, France, Germany, and the Soviet Union) to petition their government for support of nuclear fission research.

In the United States, where Fermi and Szilard had both emigrated, this led to the creation of the first man-made reactor, known as Chicago Pile-1, which achieved criticality on December 2, 1942. This work became part of the Manhattan Project, which built large reactors at the Hanford Site (formerly the town of Hanford, Washington) to breed plutonium for use in the first nuclear weapons, which were used on the cities of Hiroshima and Nagasaki. A parallel uranium enrichment effort also was pursued.

After World War II, the fear that reactor research would encourage the rapid spread of nuclear weapons and technology, combined with what many scientists thought would be a long road of development, created a situation in which the government attempted to keep reactor research under strict government control and classification. In addition, most reactor research centered on purely military purposes. There was an immediate arms and development race when the United States military refused to follow the advice of its own scientific community to form an international cooperative to share information and control nuclear materials. By 2006, things have come full circle with the Global Nuclear Energy Partnership (see below.)

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 experience partial meltdown, 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."^[17] A December 1953 speech by President Dwight Eisenhower, "Atoms for Peace," emphasized the useful harnessing of the atom and set the U.S. on a course of strong government support for international use of nuclear power.

Early years

Calder Hall nuclear power station in the United Kingdom was the world's first nuclear power station to produce electricity in commercial quantities.^[18]

The Shippingport Atomic Power Station in Shippingport, Pennsylvania was the first commercial reactor in the USA and was opened in 1957.

On June 27, 1954, the USSR's Obninsk Nuclear Power Plant became the world's first nuclear power plant to generate electricity for a power grid, and produced around 5 megawatts of electric power.^[19][20]

Later in 1954, Lewis Strauss, then chairman of the United States Atomic Energy Commission (U.S. AEC, forerunner of the U.S. Nuclear Regulatory Commission and the United States Department of Energy) spoke of electricity in the future being "too cheap to meter."^[21] The U.S. AEC itself had issued far more conservative testimony regarding nuclear fission to the U.S. Congress only months before, projecting that "costs can be brought down... [to]... about the same as the cost of electricity from conventional sources..." Strauss may have been making vague reference to hydrogen fusion - which was secret at the time - rather than uranium fission, but whatever his intent Strauss's statement was interpreted by much of the public as a promise of very cheap energy from nuclear fission. Significant disappointment would develop later on, when the new nuclear plants did not provide energy "too cheap to meter." ^[22]

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).^[18][23] The first commercial nuclear generator to become operational in the United States was the Shippingport Reactor (Pennsylvania, December, 1957).

One of the first organizations to develop 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 as well as the Shippingport Reactor. The U.S. Navy has operated more nuclear reactors than any other entity, including the Soviet Navy,^{[citation needed][dubious – discuss]} with no publicly known major incidents. The first nuclear-powered submarine, USS Nautilus (SSN-571), was put to sea in December 1954.^[24] Two U.S. nuclear submarines, USS Scorpion and USS Thresher, have been lost at sea. These vessels were both lost due to malfunctions in systems not related to the reactor plants. Also, the sites are monitored and no known leakage has occurred from the onboard reactors.

The United States Army also had a nuclear power program, beginning in 1954. The SM-1 Nuclear Power Plant, at Ft. Belvoir, Va., was the first power reactor in the US to supply electrical energy to a commercial grid (VEPCO), in April 1957, before Shippingport.

Enrico Fermi and Leó Szilárd in 1955 shared U.S. Patent 2,708,656 for the nuclear reactor, belatedly granted for the work they had done during the Manhattan Project.

Development

History of the use of nuclear power (top) and the number of active nuclear power plants (bottom).

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 worldwide capacity has risen much more slowly, reaching 366 GW in 2005. 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 cancelled.^[24] A total of 63 nuclear units were canceled in the USA between 1975 and 1980.^[25]

Washington Public Power Supply System Nuclear Power Plants 3 and 5 were never completed.

During the 1970s and 1980s rising economic costs (related to extended construction times largely due to regulatory changes and pressure-group litigation)^[26] 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.

The 1973 oil crisis had a significant effect on countries, such as France and Japan, which had relied more heavily on oil for electric generation (39% and 73% respectively) to invest in nuclear power.^[27][28] Today, nuclear power supplies about 80% and 30% of the electricity in those countries, respectively.

A general movement against nuclear power arose during the last third of the 20th century, based on the fear of a possible nuclear accident as well as the history of accidents, fears of radiation as well as the history of radiation of the public, nuclear proliferation, and on the opposition to nuclear waste production, transport and lack of any final storage plans. 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,^[29] although the public policy organization Brookings Institution suggests that new nuclear units have not been ordered in the U.S. because the Institution's research concludes they cost 15–30% more over their lifetime than conventional coal and natural gas fired plants.^[30]

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, for example lacking "robust" containment buildings.^[31] Many of these reactors are still in use today. However, changes were made in both the reactors themselves (use of low enriched uranium) and in the control system (prevention of disabling safety systems) to reduce the possibility of a duplicate accident.

An international organization to promote safety awareness and professional development on operators in nuclear facilities was created: WANO; World Association of Nuclear Operators.

Opposition in Ireland, and Poland prevented nuclear programs there, while Austria (1978), Sweden (1980) and Italy (1987) (influenced by Chernobyl) voted in referendums to oppose or phase out nuclear power. In July 2009, the Italian Parliament passed a law that canceled the results of an earlier referendum and allowed the immediate start of the Italian nuclear program.^[32]

Flexibility of nuclear power plants

It is often claimed that nuclear stations are inflexible in their output, implying that other, typically fossil stations would be used to meet peak demand. Whilst it may have been true for certain reactors, this is not longer true of at least some modern designs.^[33] Nuclear plants are routinely used in load following mode on a large scale in France.^[34]

Economics

See also Nuclear Debate below.

The economics of nuclear power plants are primarily influenced by the high initial investment necessary to construct a plant. In 2009, estimates for the cost of a new plant in the U.S. ranged from $6 to $10 billion. It is therefore usually more economical to run them as long as possible, or construct additional reactor blocks in existing facilities. In 2008, new nuclear power plant construction costs were rising faster than the costs of other types of power plants.^[35][36]. A prestigious panel assembled for a 2003 MIT study of the industry found the following:

In deregulated markets, nuclear power is not now cost competitive with coal and natural gas. However, plausible reductions by industry in capital cost, operation and maintenance costs, and construction time could reduce the gap. Carbon emission credits, if enacted by government, can give nuclear power a cost advantage.

—The Future of Nuclear Power^[37]

Comparative economics with other power sources are also discussed in the Main article above and in nuclear power debate.

Future of the industry

Diablo Canyon Power Plant in San Luis Obispo County, California, USA

As of 2007, Watts Bar 1, which came on-line in February 7, 1996, 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, even in the U.S. and throughout Europe, investment in research and in the nuclear fuel cycle has continued, and some nuclear industry experts^[38] predict electricity shortages, fossil fuel price increases, global warming and heavy metal emissions from fossil fuel use, new technology such as passively safe plants, and national energy security will renew the demand for nuclear power plants.

According to the World Nuclear Association, globally during the 1980s one new nuclear reactor started up every 17 days on average, and by the year 2015 this rate could increase to one every 5 days.^[39]

Brunswick Nuclear Plant discharge canal.

Many countries remain active in developing nuclear power, including Pakistan, 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). Several EU member states actively pursue nuclear programs, while some other member states continue to have a ban for the nuclear energy use. 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 loan guarantees 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 21st 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 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.

There is a possible impediment to production of nuclear power plants as only a few companies worldwide have the capacity to forge single-piece containment vessels,^[40] which reduce the risk of a radiation leak. Utilities across the world are submitting orders years in advance of any actual need for these vessels. Other manufacturers are examining various options, including making the component themselves, or finding ways to make a similar item using alternate methods.^[41] Other solutions include using designs that do not require single-piece forged pressure vessels such as Canada's Advanced CANDU Reactors or Sodium-cooled Fast Reactors.

This graph illustrates the potential rise in CO₂ emissions if base-load electricity currently produced in the U.S. by nuclear power were replaced by coal or natural gas as current reactors go offline after their 60 year licenses expire. Note: graph assumes all 104 American nuclear power plants receive license extensions out to 60 years.

The World Nuclear Industry Status Report 2009 states that "even if Finland and France each builds a reactor or two, China goes for an additional 20 plants and Japan, Korea or Eastern Europe add a few units, the overall worldwide trend will most likely be downwards over the next two decades".^[42] With long lead times of 10 years or more, it will be difficult to maintain or increase the number of operating nuclear power plants over the next 20 years. The one exception to this outcome would be if operating lifetimes could be substantially increased beyond 40 years on average. This seems unlikely since the present average age of the operating nuclear power plant fleet in the world is 25 years.^[42]

However, China plans to build more than 100 plants,^[43] while in the US the licenses of almost half its reactors have already been extended to 60 years,^[44] and plans to build more than 30 new ones are under consideration.^[45] Further, the U.S. NRC and the U.S. Department of Energy have initiated research into Light water reactor sustainability which is hoped will lead to allowing extensions of reactor licenses beyond 60 years, in increments of 20 years, provided that safety can be maintained, as the loss in non-CO₂-emitting generation capacity by retiring reactors "may serve to challenge U.S. energy security, potentially resulting in increased greenhouse gas emissions, and contributing to an imbalance between electric supply and demand."^[46] In 2008, the International Atomic Energy Agency (IAEA) predicted that nuclear power capacity could double by 2030, though that would not be enough to increase nuclear's share of electricity generation.^[47]

Nuclear reactor technology

Cattenom Nuclear Power Plant.

Just as many conventional thermal power stations generate electricity by harnessing the thermal energy released from burning fossil fuels, nuclear power plants convert the energy released from the nucleus of an atom, typically via nuclear fission.

When a relatively large fissile atomic nucleus (usually uranium-235 or plutonium-239) absorbs a neutron, a fission of the atom often results. Fission splits the atom into two or more smaller nuclei with kinetic energy (known as fission products) and also releases gamma radiation and free neutrons.^[48] A portion of these neutrons may later be absorbed by other fissile atoms and create more fissions, which release more neutrons, and so on.^[49]

This nuclear chain reaction can be controlled by using neutron poisons and neutron moderators to change the portion of neutrons that will go on to cause more fissions.^[49] Nuclear reactors generally have automatic and manual systems to shut the fission reaction down if unsafe conditions are detected.^[50]

A cooling system removes heat from the reactor core and transports it to another area of the plant, where the thermal energy can be harnessed to produce electricity or to do other useful work. Typically the hot coolant will be used as a heat source for a boiler, and the pressurized steam from that boiler will power one or more steam turbine driven electrical generators.^[51]

There are many different reactor designs, utilizing different fuels and coolants and incorporating different control schemes. Some of these designs have been engineered to meet a specific need. Reactors for nuclear submarines and large naval ships, for example, commonly use highly enriched uranium as a fuel. This fuel choice increases the reactor's power density and extends the usable life of the nuclear fuel load, but is more expensive and a greater risk to nuclear proliferation than some of the other nuclear fuels.^[52]

A number of new designs for nuclear power generation, collectively known as the Generation IV reactors, are the subject of active research and may be used for practical power generation in the future. Many of these new designs specifically attempt to make fission reactors cleaner, safer and/or less of a risk to the proliferation of nuclear weapons. Passively safe plants (such as the ESBWR) are available to be built^[53] and other designs that are believed to be nearly fool-proof are being pursued.^[54] Fusion reactors, which may be viable in the future, diminish or eliminate many of the risks associated with nuclear fission.^[55]

Life cycle

The Nuclear Fuel Cycle begins when uranium is mined, enriched, and manufactured into nuclear fuel, (1) which is delivered to a nuclear power plant. After usage in the power plant, the spent fuel is delivered to a reprocessing plant (2) or to a final repository (3) for geological disposition. In reprocessing 95% of spent fuel can be recycled to be returned to usage in a power plant (4).

A nuclear reactor is only part of the life-cycle for nuclear power. The process starts with mining (see Uranium mining). Uranium mines are underground, open-pit, or in-situ leach mines. In any 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% 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 operational cycles (typically 6 years total now) inside the reactor, generally until about 3% 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 and thermally cool enough to handle, and it can be moved to dry storage casks or reprocessed.

Conventional fuel resources

Uranium is a fairly common element in the Earth's crust. Uranium is approximately as common as tin or germanium in Earth's crust, and is about 35 times more common than silver. Uranium is a constituent of most rocks, dirt, and of the oceans. The fact that uranium is so spread out is a problem because mining uranium is only economically feasible where there is a large concentration. Still, the world's present measured resources of uranium, economically recoverable at a price of 130 USD/kg, are enough to last for "at least a century" at current consumption rates.^[56][57] This represents a higher level of assured resources than is normal for most minerals. On the basis of analogies with other metallic minerals, a doubling of price from present levels could be expected to create about a tenfold increase in measured resources, over time. However, the cost of nuclear power lies for the most part in the construction of the power station. Therefore 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% and the electricity cost about 7%, whereas doubling the price of natural gas would typically add 70% to the price of electricity from that source. At high enough prices, eventually extraction from sources such as granite and seawater become economically feasible.^[58][59]

Current light water reactors make relatively inefficient use of nuclear fuel, fissioning only the very rare uranium-235 isotope. Nuclear reprocessing can make this waste reusable and more efficient reactor designs allow better use of the available resources.^[60]

Breeding

As opposed to current light water reactors which use uranium-235 (0.7% of all natural uranium), fast breeder reactors use uranium-238 (99.3% of all natural uranium). It has been estimated that there is up to five billion years’ worth of uranium-238 for use in these power plants.^[61]

Breeder technology has been used in several reactors, but the high cost of reprocessing fuel safely requires uranium prices of more than 200 USD/kg before becoming justified economically.^[62] 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 — Russia 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 in the thorium fuel cycle. Thorium is about 3.5 times as common as uranium in the Earth's crust, and has different geographic characteristics. This would extend the total practical fissionable resource base by 450%.^[63] Unlike the breeding of U-238 into plutonium, fast breeder reactors are not necessary — it can be performed satisfactorily in more conventional plants. India has looked into this technology, as it has abundant thorium reserves but little uranium.

Fusion

Fusion power advocates commonly propose the use of deuterium, or tritium, both isotopes of hydrogen, as fuel and in many current designs also lithium and boron. 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.^[64] Although this process has yet to be realized, many experts and civilians alike believe fusion to be a promising future energy source due to the short lived radioactivity of the produced waste, its low carbon emissions, and its prospective power output.

Water

Like all forms of power generation using steam turbines, nuclear power plants use large amounts of water for cooling. At Sellafield, which is no longer producing electricity, a maximum of 18,184.4 m³ a day (over 4 million gallons) and 6,637,306 m³ a year (figures from the Environment Agency) of fresh water from Wast Water is still abstracted to use on site for various processes. As with most power plants, two-thirds of the energy produced by a nuclear power plant goes into waste heat (see Carnot cycle), and that heat is carried away from the plant in the water (which remains uncontaminated by radioactivity). The emitted water either is sent into cooling towers where it goes up and is emitted as water droplets (literally a cloud) or is discharged into large bodies of water — cooling ponds, lakes, rivers, or oceans.^[65] Droughts can pose a severe problem by causing the source of cooling water to run out.^[66][67]

The Palo Verde Nuclear Generating Station near Phoenix, AZ is the only nuclear generating facility in the world that is not located adjacent to a large body of water. Instead, it uses treated sewage from several nearby municipalities to meet its cooling water needs, recycling 20 billion US gallons (76,000,000 m³) of wastewater each year.

Like conventional power plants, nuclear power plants generate large quantities of waste heat which is expelled in the condenser, following the turbine. Colocation of plants that can take advantage of this thermal energy has been suggested by Oak Ridge National Laboratory (ORNL) as a way to take advantage of process synergy for added energy efficiency. One example would be to use the power plant steam to produce hydrogen from water.^[68] (Separation of water into hydrogen and oxygen can use less energy if the water begins at a high temperature.)

Solid waste

The safe storage and disposal of nuclear waste is a significant challenge and yet unresolved problem. The most important waste stream from nuclear power plants is spent fuel. A large nuclear reactor produces 3 cubic metres (25–30 tonnes) of spent fuel each year.^[69] It is primarily composed of unconverted uranium as well as significant quantities of transuranic actinides (plutonium and curium, mostly). In addition, about 3% 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.^[70]

High-level radioactive waste

Spent fuel is highly radioactive and needs to be handled with great care and forethought. However, spent nuclear fuel becomes less radioactive over the course of thousands of years of time. After about 5 percent of the rod has reacted the rod is no longer able to be used. Today, scientists are experimenting on how to recycle these rods to reduce waste. In the meantime, after 40 years, the radiation flux is 99.9% lower than it was the moment the spent fuel was removed, although still dangerously radioactive.^[60]

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 fission products, 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 or millennia, 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 2007, the United States had accumulated more than 50,000 metric tons of spent nuclear fuel from nuclear reactors.^[71] Underground storage at Yucca Mountain nuclear waste repository in 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.^{[citation needed]}

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.^{[citation needed]} 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.^[72] It has been argued^[who?] that the best solution for the nuclear waste is above ground temporary storage since technology is rapidly changing. There is hope that current waste may well become a valuable resource in the future.

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.^[73] France reprocesses its nuclear waste to reduce its mass and make more energy.^[74] However, the article continues, "Today we stock containers of waste because currently scientists don't know how to reduce or eliminate the toxicity, but maybe in 100 years perhaps scientists will... Nuclear waste is an enormously difficult political problem which to date no country has solved. It is, in a sense, the Achilles heel of the nuclear industry... If France is unable to solve this issue, says Mandil, then 'I do not see how we can continue our nuclear program.'"^[74] Further, reprocessing itself has its critics, such as the Union of Concerned Scientists.^[75]

Low-level radioactive waste

The nuclear industry also produces a huge 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, et cetera.^{[citation needed]} Most low-level waste releases very low levels of radioactivity and is only considered radioactive waste because of its history.^[76]

Comparing radioactive waste to industrial toxic waste

In countries with nuclear power, radioactive wastes comprise less than 1% 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.^[60] 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.

Recent reports claim that coal power actually results in more radioactive waste being released into the environment than nuclear power, and that the population effective dose equivalent from radiation from coal plants is 100 times as much as nuclear plants.^[77] However, reputable journals point out that coal ash is not more radioactive than nuclear waste, and the differences in exposure lie in the fact that nuclear plants use heavy shielding to protect the environment from the heavily irradiated reactor vessel, fuel rods, and any radioactive waste on site.^[78]

Reprocessing

Reprocessing can potentially recover up to 95% of the remaining uranium and plutonium in spent nuclear fuel, putting it into new mixed oxide fuel. This produces 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%. Reprocessing of civilian fuel from power reactors is currently done on large scale in Britain, France and (formerly) Russia, soon will be done in China and perhaps India, and is being done on an expanding scale in Japan. The full 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% (by mass) of the yearly fuel use, 7% within France and another 21% in Russia.^[79]

Unlike other countries, the US stopped civilian reprocessing from 1976 to 1981 as one part of US non-proliferation policy, since reprocessed material such as plutonium could be used in nuclear weapons: however, reprocessing is now allowed in the U.S.^[80] Even so, in the U.S. spent nuclear fuel is currently all treated as waste.^[81]

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.^[82]

Depleted uranium

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 armor—as it has a higher density than lead. Depleted uranium is also useful in munitions as DU penetrators (bullets or APFSDS tips) "self sharpen", due to uranium's tendency to fracture along shear bands.^[83][84]

There are concerns that U-238 may lead to health problems in groups exposed to this material excessively, such as tank crews and civilians living in areas where large quantities of DU ammunition have been used in shielding, bombs, missile warheads, and bullets. In January 2003 the World Health Organization released a report finding that contamination from DU munitions were localized to a few tens of meters from the impact sites and contamination of local vegetation and water was 'extremely low'. The report also states that approximately 70% of ingested DU will leave the body after twenty four hours and 90% after a few days.^[85]

Debate on nuclear power

Proponents of nuclear energy contend that nuclear power is a sustainable energy source that does not create air pollution, reduces carbon emissions and increases energy security by decreasing dependence on foreign oil.^[86] The operational safety record of nuclear plants in the Western world is far better when compared to the other major types of power plants. With the exception of Chernobyl, no radiation-related fatalities ever occurred at any commercial nuclear power plant.^[87] Optimists point out that the volume of radioactive waste is very small, and claim it can be stored safely deep underground. Future designs of reactors are promised to eliminate almost all waste.

Critics believe that nuclear power is a potentially dangerous energy source, with decreasing proportion of nuclear energy in production. They claim that radioactive waste cannot be stored safely for long periods of time, that there is a continuing possibility of radioactive contamination by accident or sabotage, and that exporting nuclear technology to other countries might lead to the proliferation of nuclear weapons. The recent slow rate of growth of installed nuclear capacity is said to indicate that nuclear reactors cannot be built fast enough to slow down climate change.^[88] Nuclear power plants are also criticized due to their centralized generation of electricity.

Arguments of economics and safety are used by both sides of the debate.

See also

Nuclear technology portal

Energy portal

Footnotes

References

• An entry to nuclear power through an educational discussion of reactors
• The Nuclear Energy Option, online book by Bernard L. Cohen.
• Steve Thomas (2005), "The Economics of Nuclear Power: analysis of recent studies"PDF (305 KB), PSIRU, University of Greenwich, UK
• Nuclear power information archives from ALSOS, the National Digital Science Library at Washington & Lee University.
• Texas Will Host First New U.S. Nuclear Plants since 1970s

Further reading

• Cravens, Gwyneth (2007). Power to Save the World: the Truth about Nuclear Energy. New York: Knopf. pp. 464. ISBN 0307266567. http://cravenspowertosavetheworld.com/. 
• Ferguson, Charles D., "Nuclear Energy: Balancing Benefits and Risks", Council on Foreign Relations, 2007

External links

Find more about Nuclear power on Wikipedia's sister projects:

Definitions from Wiktionary
Textbooks from Wikibooks
Quotations from Wikiquote
Source texts from Wikisource
Images and media from Commons
News stories from Wikinews
Learning resources from Wikiversity

• Alsos Digital Library for Nuclear Issues — Annotated Bibliography on Nuclear Power
• An entry to nuclear power through an educational discussion of reactors
• Argonne National Laboratory — Maps of Nuclear Power Reactors
• Boiling Water Reactor Plant, BWR Simulator Program
• Briefing Papers from the Australian EnergyScience Coaltion
• British Energy — Understanding Nuclear Energy / Nuclear Power
• Coal Combustion: Nuclear Resource or Danger?
• Congressional Research Service report on Nuclear Energy PolicyPDF (94.0 KB)
• Energy Information Administration provides lots of statistics and information
• Environmental impacts of nuclear power according to the United States Environmental Protection Agency‎ at EPA.gov
• How Nuclear Power Works
• IAEA Website The International Atomic Energy Agency
  • IAEA's Power Reactor Information System (PRIS)
  • IAEA's Web directory of nuclear related resources on the Internet
• Idaho National Laboratory's Nuclear Research
  • Information about all NPP in the world
• Nuclear Power Education
• Nuclear Tourist.com, nuclear power information
• Nuclear Waste Disposal Resources
• The World Nuclear Industry Status Report 2007.
• Wilson Quarterly — Nuclear Power: Both Sides
• Nuclear Power Related News
• Relative costs of wind, coal and nuclear power

Nuclear news websites

• An up to date selection of US and international news on nuclear issues
• ANS Nuclear Clips
• Nuclear News
• World Nuclear News

Against

• Why we don't need nuclear power
• 1 million Europeans against nuclear power
• Beyond Nuclear at Nuclear Policy Research Institute advocacy organization
• Campaign for Nuclear Phaseout (CNP)
• Climate Change and Nuclear EnergyPDF (265 kB)
• Critical assessment of the US-India nuclear energy accord published by the Internationalist Review* Critical Hour: Three Mile Island, The Nuclear Legacy, And National SecurityPDF (929 KB) Online book
• Greenpeace: End the nuclear age and Nuclear Reaction blog.
• Greenpeace — Calendar of Nuclear Accidents
• Natural Resources Defense CouncilPDF (158 KB)
• Nuclear Files
• Sierra Club
• World Information Service on Energy (WISE)

Supportive

• American Nuclear Society (ANS)
• Atomic Insights
• Environmentalists for Nuclear Power
• Foratom: The European Atomic Forum
• Freedom for Fission
• Nuclear Energy Institute (NEI)
• Nuclear is Our Future
• Representing the People and Organisations of the Global Nuclear Profession
• SCK•CEN: Belgian Nuclear Research Centre
• The Nuclear Energy Option, online book by Bernard L. Cohen. Emphasis on risk estimates of nuclear.
• World Nuclear Association
• Nuclear Power an Alternate Energy Power Point Slides
• Pros and Cons of Nuclear Power Power Point Slides