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article on Nuclear Energy
Nuclear power is the controlled use of nuclear reactions to release energy for work including propulsion, heat, and the generation of electricity. Human use of nuclear power to do significant useful work is currently limited to nuclear fission and radioactive decay. Nuclear energy is produced when a fissile material, such as uranium-235 (235U), is concentrated such that nuclear fission takes place in a controlled 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. Nuclear power is used to power most military submarines and aircraft carriers and provides 7% of the world's energy and 15.7% of the world's electricity.
2.2 Early years
3 Reactor types
3.1 Current technology
3.2 How it works
3.3 Experimental technologies
4 Life cycle
4.1 Fuel resources
4.2 Solid waste
5.1 Capital costs
5.2 Operating costs
5.4 Other economic issues
6 Concerns about nuclear power
6.1 Accident or attack
6.2 Health effects on populations
6.3 Nuclear proliferation
7 Environmental effects
7.1 Air pollution
7.2 Waste heat in water systems
8 List of atomic energy groups
10 See also
10.1 Nuclear power by country
10.2 USAEC/USNRC studies of risk
The United States produces the most nuclear energy, with nuclear power providing 20% of the electricity it consumes, while France produces the highest percentage of its electrical energy from nuclear reactors—80% as of 2006. In the European Union as a whole, nuclear energy provides 30% of the electricity. Nuclear energy policy differs between countries.
Nuclear energy uses an abundant, widely distributed fuel, and mitigates the Greenhouse Effect if used to replace fossil-fuel-derived electricity. International research is ongoing into various safety improvements, the use of nuclear fusion and additional uses such as the generation of hydrogen (in support of hydrogen economy schemes), for desalinating sea water, and for use in district heating systems. Construction of nuclear power plants in the U.S. declined following the 1979 Three Mile Island accident and the 1986 disaster at Chernobyl. Lately, there has been renewed interest in nuclear energy from national governments due to economic and environmental concerns. Other reasons for interest include the public, some notable environmentalists due to increased oil prices, new passively safe designs of plants, and the low emission rate of greenhouse gas which some governments need to meet the standards of the Kyoto Protocol. A few reactors are under construction, and several new types of reactors are planned.
The use of nuclear power is controversial because of the problem of storing radioactive waste for indefinite periods, the potential for possibly severe radioactive contamination by accident or sabotage, and the possibility that its use in some countries could lead to the proliferation of nuclear weapons. Proponents believe 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 other fossil-fuel plants, that it releases much less radioactive waste than coal power, and that nuclear power is a sustainable energy source. Critics, including most major environmental groups, believe nuclear power is an uneconomic, unsound and potentially dangerous energy source, especially compared to renewable energy, and dispute whether the costs and risks can be reduced through new technology. 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 the claims against Iran.
The first successful experiment with nuclear fission was conducted in 1938 in Berlin by the German physicists Otto Hahn, Lise Meitner and Fritz Strassmann.
During the Second World War, a number of nations embarked on crash programs to develop nuclear energy, focusing first on the development of nuclear reactors. The first self-sustaining nuclear chain reaction was obtained at the University of Chicago by Enrico Fermi on December 2, 1942, and reactors based on his research were used to produce the plutonium necessary for the "Fat Man" weapon dropped on Nagasaki, Japan. Several nations began their own construction of nuclear reactors at this point, primarily for weapons use, though research was also being conducted into their use for civilian electricity generation.
Electricity was generated for the first time by a nuclear reactor on December 20, 1951 at the EBR-I experimental fast breeder station near Arco, Idaho, which initially produced about 100 kW.
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.
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 world's first nuclear power plant to generate electricity for a power grid started operations at Obninsk, USSR. The reactor was graphite moderated, water cooled and had a capacity of 5 megawatts (MW). The world's first commercial nuclear power station, Calder Hall in Sellafield, England was opened in 1956, a gas-cooled Magnox reactor with an initial capacity of 50 MW (later 200 MW). The Shippingport Reactor (Pennsylvania, 1957), a pressurized water reactor, was the first commercial nuclear generator to become operational in the United States.
In 1954, the chairman of the United States Atomic Energy Commission (forerunner of the U.S. Nuclear Regulatory Commission) talked about electricity being "too cheap to meter" in the future, often misreported as a concrete statement about nuclear power, and foresaw 1000 nuclear plants on line in the USA by the year 2000.
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).
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 cancelled.
Washington Public Power Supply System Nuclear Power Plants 3 and 5 were never completedDuring 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 20th century, based on the fear of a possible nuclear accident and on fears of radiation, and on the 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 key part in stopping new plant construction in many countries. Austria (1978), Sweden (1980) and Italy (1987) voted in referendums to oppose or phase out nuclear power, while opposition in Ireland prevented a nuclear programme there. However, the Brookings Institution suggests that new nuclear units have not been ordered in the US primarily for economic reasons rather than fears of accidents.
There are two types of nuclear power in current use:
The nuclear fission reactor produces heat through a controlled nuclear chain reaction in a critical mass of fissile material.
All current nuclear power plants are critical fission reactors, which are the focus of this article. The output of fission reactors is controllable. There are several subtypes of critical fission reactors, which can be classified as Generation I, Generation II and Generation III. All reactors will be compared to the Pressurized Water Reactor (PWR), as that is the standard modern reactor design.
The difference between fast-spectrum and thermal-spectrum reactors will be covered later. In general, fast-spectrum reactors will produce less waste, and the waste they do produce will have a vastly shorter halflife, but they are more difficult to build, and more expensive to operate. Fast reactors can also be breeders, whereas thermal reactors generally cannot.
A. Pressurized Water Reactors (PWR)
These are reactors cooled and moderated by high pressure liquid (even at extreme temperatures) water. They are the majority of current reactors, and are generally considered the safest and most reliable technology currently in large scale deployment, although Three Mile Island is a reactor of this type. This is a thermal neutron reactor design.
B. Boiling Water Reactors (BWR)
These are reactors cooled and moderated by water, under slightly lower pressure. The water is allowed to boil in the reactor. The thermal efficiency of these reactors can be higher, and they can be simpler, and even potentially more stable and safe. Unfortunately, the boiling water puts more stress on many of the components, and increases the risk that radioactive water may escape in an accident. These reactors make up a substantial percentage of modern reactors. This is a thermal neutron reactor design.
C. Pressurized Heavy Water Reactor (PHWR)
A Canadian design, (known as CANDU) these reactors are heavy-water-cooled and -moderated Pressurized-Water reactors. Instead of using a single large pressure vessel as in a PWR, the fuel is contained in hundreds of pressure tubes. These reactors are fuelled with natural uranium and are thermal neutron reactor designs. PHWRs can be refueled while at full power, which makes them very efficient in their use of uranium (it allows for precise flux control in the core). Most PHWRs exist within Canada, but units have been sold to Argentina, China, India (pre-NPT), Pakistan (pre-NPT), Romania, and South Korea. India also operates a number of PHWR's, often termed 'CANDU-derivatives', built after the 1974 Smiling Buddha nuclear weapon test.
D. Reaktor Bolshoy Moshchnosti Kanalniy (RBMK)
A Soviet Union design, built to produce plutonium as well as power. RBMKs are water cooled with a graphite moderator. RBMKs are in some respects similar to CANDU in that they are refuelable On-Load and employ a pressure tube design instead of a PWR-style pressure vessel. However, unlike CANDU they are very unstable and too large to have containment buildings making them dangerous in the case of an accident. A series of critical safety flaws have also been identified with the RBMK design, though some of these were corrected following the Chernobyl accident. RBMK reactors are generally considered one of the most dangerous reactor designs in use. Chernobyl was an RBMK.
E. Gas Cooled Reactor (GCR) and Advanced Gas Cooled Reactor (AGCR)
These are generally graphite moderated and CO2 cooled. They have a high thermal efficiency compared with PWRs and an excellent safety record. There are a number of operating reactors of this design, mostly in the United Kingdom. Older designs (i.e. Magnox stations) are either shut down or will be in the near future. However, the AGCRs have an anticipated life of a further 10 to 20 years. This is a thermal neutron reactor design.
F. Super Critical Water-cooled Reactor (SCWR)
This is a theoretical reactor design that is part of the Gen-IV reactor project. It combines higher efficiency than a GCR with the safety of a PWR, though it is perhaps more technically challenging than either. The water is pressurized and heated past its critical point, until there is no difference between the liquid and gas states. An SCWR is similar to a BWR, except there is no boiling (as the water is critical), and the thermal efficiency is higher as the water behaves more like a classical gas. This is an epithermal neutron reactor design.
G. Liquid Metal Fast Breeder Reactor (LMFBR)
This is a reactor design that is cooled by liquid metal, totally unmoderated, and produces more fuel than it consumes. These reactors can function much like a PWR in terms of efficiency, and do not require much high pressure containment, as the liquid metal does not need to be kept at high pressure, even at very high temperatures. Superphénix in France was a reactor of this type, as was Fermi-I in the United States. The Monju reactor in Japan suffered a sodium leak in 1995 and is approved for restart in 2008. All three use/used liquid sodium. These reactors are fast neutron, not thermal neutron designs. These reactors come in two types:
Using lead as the liquid metal provides excellent radiation shielding, and allows for operation at very high temperatures. Also, lead is (mostly) transparent to neutrons, so fewer neutrons are lost in the coolant, and the coolant does not become radioactive. Unlike sodium, lead is mostly inert, so there is less risk of explosion or accident, but such large quantities of lead may be problematic from toxicology and disposal points of view. Often a reactor of this type would use a lead-bismuth eutectic mixture. In this case, the bismuth would present some minor radiation problems, as it is not quite as transparent to neutrons, and can be transmuted to a radioactive isotope more readily than lead.
Most LMFBRs are of this type. The sodium is relatively easy to obtain and work with, and it also manages to actually prevent corrosion on the various reactor parts immersed in it. However, sodium explodes violently when exposed to water, so care must be taken, but such explosions wouldn't be vastly more violent than (for example) a leak of superheated fluid from a SCWR or PWR.
The radioisotope thermoelectric generator produces heat through passive radioactive decay.
Some radioisotope thermoelectric generators have been created to power space probes (for example, the Cassini probe), some lighthouses in the former Soviet Union, and some pacemakers. The heat output of these generators diminishes with time; the heat is converted to electricity utilising the thermoelectric effect.
For more details on this topic, see Nuclear power plant.
How it works
The key components common to most types of nuclear power plants are:
Emergency core cooling systems
Reactor protective system
Steam generators (not in BWRs)
Boiler feedwater pump
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. (see enriched
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.
Integral Fast Reactor — The link at the end of this
paragraph references an interview with Dr. Charles Till, former director of
Argonne National Laboratory West in Idaho and outlines the Integral Fast
Reactor and its advantages over current reactor design, especially in the
areas of safety, efficient nuclear fuel usage and reduced waste. The IFR was
built, tested and evaluated during the 1980s and then retired under the Clinton
administration in the 1990s due to nuclear non-proliferation policies of the
administration. Recycling spent fuel is the core of its design and it
therefore produces a fraction of the waste of current reactors.
Pebble Bed Reactor — This reactor type is designed so high temperatures reduce power output by doppler broadening of the fuel's neutron cross-section. It uses ceramic fuels so its safe operating temperatures exceed the power-reduction temperature range. Most designs are cooled by inert helium, which cannot have steam explosions, and which does not easily absorb neutrons and become radioactive, or dissolve contaminants that can become radioactive. Typical designs have more layers (up to 7) of passive containment than light water reactors (usually 3). A unique feature that might aid safety is that the fuel-balls actually form the core's mechanism, and are replaced one-by-one as they age. The design of the fuel makes fuel reprocessing expensive.
SSTAR, Small, Sealed, Transportable, Autonomous Reactor is being primarily researched and developed in the US, intended as a fast breeder reactor that is tamper resistant and passively safe.
Subcritical reactors are designed to be safer and more stable, but pose a number of engineering and economic difficulties.
Controlled nuclear fusion could in principle be used in fusion power plants to produce safer, cleaner power, 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.
Thorium based reactors
It is possible to convert Thorium-232 into U-233 in reactors specially designed for the purpose. In this way, Thorium, which is more plentiful than uranium, can be used to breed U-233 nuclear fuel. U-233 is also believed to have favourable nuclear properties as compared to traditionally used U-235, including better neutron economy and lower production of long lived transuranic waste.
Advanced Heavy Water Reactor — A proposed heavy water moderated nuclear power reactor that will be the next generation design of the PHWR type. Under development in the Bhabha Atomic Research Centre (BARC).
KAMINI — A unique reactor using Uranium-233 isotope for fuel. Built by BARC and IGCAR Uses thorium.
India is also building a bigger scale FBTR or fast breeder thorium reactor to harness the power with the use of thorium.
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).
Nuclear fuel — a compact, inert, insoluble solid.Main article: Nuclear fuel cycle
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% 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% 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, occurring almost everywhere on land and in the oceans. It is about as common as tin, and 500 times more common than gold. Most types of rocks and soils contain uranium, although often in low concentrations. At present, economically viable deposits are regarded as being those with concentrations of at least 0.1% uranium. At this cost level, available reserves would last for 50 years at the present rate of use. Doubling the price of uranium, which would have only little effect on the overall cost of nuclear power, would increase reserves to hundreds of years. To put this in perspective; a doubling in the cost of natural uranium would increase the total cost of nuclear power by 5%. On the other hand, if the price of natural gas was doubled, the cost of gas-fired power would increase by about 60%. Doubling the price of coal would increase the cost of power production in a large coal-fired power station by about 30%.
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.
Current light water reactors make relatively inefficient use of nuclear fuel, leading to energy waste. More efficient reactor designs or nuclear reprocessing would reduce the amount of waste material generated and allow better use of the available resources.
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. Breeder technology has been used in several reactors. Currently (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 — 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.
Proposed fusion reactors assume the use of deuterium, an isotope of hydrogen, as fuel and in most 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 3,000 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. For comparison, the Sun has an estimated remaining life of 5 billion years.
The predominant 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. 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.
Spent fuel is highly radioactive and needs to be handled
with great care and forethought. Fresh from the reactor, it is so radioactive
that less than a minute's exposure to it will cause death. However, spent
nuclear fuel becomes less radioactive over time. After 40 years, the
radiation flux is 99.9% lower than it was the moment the spent fuel was
removed, although still dangerously radioactive.
The safe storage and disposal of nuclear waste is a significant challenge. Because of potential harm from radiation, spent nuclear fuel must be stored in shielded basins of water (spent fuel pools), and usually subsequently in dry storage vaults or dry cask storage 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 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. See the article on the nuclear fuel cycle for more information.
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, etc. 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% 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.
Reprocessing can recover up to 95% of the remaining
uranium and plutonium in spent nuclear fuel, putting it into new mixed oxide fuel.
This also 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,
will be in China and perhaps India, and is being done on an expanding scale
in Japan. Iran has announced its intention to complete the nuclear fuel cycle
via reprocessing, a move which has led to criticism from the United States
and the International Atomic Energy Agency. Unlike other countries, U.S.
policy at one stage forbade recycling of used fuel; although this policy was
reversed, spent fuel is all currently treated as waste.
Nuclear power plants typical have relatively high capital costs for building the plant but relatively low operating and maintenance costs (which typically include the full cost of spent fuel processing and disposal). As such, comparison with other power generation methods is strongly dependent on assumptions about capital financing and construction timescales for nuclear.
Opponents of nuclear power argue that the costs related to construction and operation of nuclear power plants, including costs for spent-fuel disposal and plant retirement, outweigh the environmental benefits. Proponents of nuclear power respond that nuclear energy is the only power source which explicitly factors the estimated costs for waste containment and plant decommissioning into its overall cost, and that the quoted cost of fossil fuel plants is deceptively low for this reason. The cost of some renewables would be increased too if they included necessary back-up due to their intermittent nature.
A UK Royal Academy of Engineering report in 2004 looked at electricity generation costs from new plants in the UK. In particular it aimed to develop "a robust approach to compare directly the costs of intermittent generation with more dependable sources of generation". This meant adding the cost of standby capacity for wind, as well as carbon values up to £30 (€45.44) per tonne CO2 for coal and gas. Wind power was calculated to be more than twice as expensive as nuclear power. Without a carbon tax, the cost of production through coal, nuclear and gas ranged £0.022-0.026/kWh and coal gasification was £0.032/kWh. When carbon tax was added (up to £0.025) coal came close to onshore wind (including back-up power) at £0.054/kWh — offshore wind is £0.072/kWh.
Nuclear power remained at £0.023/kWh either way, as it produces negligible amounts of CO2. Nuclear figures included decommissioning costs.
In one study, certain gas cogeneration plants were
calculated to be three to four times more cost-effective than nuclear power,
if all the heat produced was used onsite or in a local heating system.
However, the study estimated only 25 year plant lifetimes (60 is now common),
68% capacity factors were assumed (above 90% is now common), other
conservatisms were applied, and nuclear power also produces heat which could
be used in similar ways (although most nuclear power plants are located in
remote areas). The study then found similar costs for nuclear power and most
other forms of generation if not including external costs (such as back-up
Generally, a nuclear power plant is significantly more expensive to build than an equivalent coal-fuelled or gas-fuelled plant. Coal is significantly more expensive than nuclear fuel, and natural gas significantly more expensive than coal — thus, capital costs aside, natural gas-generated power is the most expensive. However, servicing the capital costs for a nuclear power dominate the costs of nuclear-generated electricity, contributing about 70% of costs (assuming a 10% discount rate).
The recent liberalisation of the electricity market in many countries has made the economics of nuclear power generation less attractive. Previously a monopolistic provider could guarantee output requirements decades into the future. Private generating companies have to accept shorter output contracts and the risks of future competition, so desire a shorter return on investment period which favours generation plants with lower capital costs.
In many countries, licensing, inspection and certification of nuclear power plants has added delays and construction costs to their construction. In the U.S. many new regulations were put in place after the Three Mile Island partial meltdown. Gas-fired and coal-fired plants do not face such regulations. Because a power plant does not yield profits during construction, longer construction times translate directly into higher interest charges on borrowed construction funds. However, the regulatory processes for siting, licensing, and constructing have been standardized since their introduction, to make construction of newer and safer designs more attractive to companies.
In Japan and France, construction costs and delays are significantly diminished because of streamlined government licensing and certification procedures. In France, one model of reactor was type-certified, using a safety engineering process similar to the process used to certify aircraft models for safety. That is, rather than licensing individual reactors, the regulatory agency certified a particular design and its construction process to produce safe reactors. U.S. law permits type-licensing of reactors, a process which is about to be used.
To encourage development of nuclear power, under the Nuclear Power 2010 Program the U.S. Department of Energy (DOE) has offered interested parties the opportunity to introduce France's model for licensing and to subsidize 25% to 50% of the construction cost overruns due to delays for the first six new plants. Several applications were made, two sites have been chosen to receive new plants, and other projects are pending.
In general, coal and nuclear plants have the same types of operating costs (operations and maintenance plus fuel costs). However, nuclear and coal differ in the relative size of those costs. Nuclear has lower fuel costs but higher operating and maintenance costs. In recent times in the United States savings due to lower fuel cost have not been low enough for nuclear to repay its higher investment cost. Thus no new nuclear reactors have been ordered in the United States since the 1970s. Coal's operating cost advantages have only rarely been sufficient to encourage the construction of new coal based power generation. Around 90 to 95 percent of new power plant construction in the United States has been natural gas-fired.
To be competitive in the current market, both the nuclear and coal industries must reduce new plant investment costs and construction time. The burden is clearly greater for nuclear producers than for coal producers, because investment costs are higher for nuclear plants. Operation and maintenance costs are particularly important because they represent a large portion of costs for nuclear power.
One of the primary reasons for the uncompetitiveness of the U.S. nuclear industry has been the lack of any measure that provides an economic incentive to reduce carbon emissions (carbon tax). Many economists and environmentalists have called for a mechanism to take into account the negative externalities of coal and gas consumption. In such an environment, it is argued that nuclear will become cost-competitive in the United States.
Critics of nuclear power claim that it is the beneficiary
of inappropriately large economic subsidies — mainly taking the forms of
taxpayer-funded research and development and limitations on disaster
liability — and that these subsidies, being subtle and indirect, are often
overlooked when comparing the economics of nuclear against other forms of
power generation. However, competing energy sources also receive subsidies.
Fossil fuels receive large direct and indirect subsidies, such as tax
benefits and not having to pay for the Greenhouse gases they emit. Renewables
receive large direct production subsidies and tax breaks in many nations.
Energy research and development (R&D) for nuclear
power has and continues to receive much larger state subsidies than R&D
for renewable energy or fossil fuels. However, today most of this takes
places in Japan and France: in most other nations renewable R&D get more
money. In the U.S., public research money for nuclear fission declined from
2,179 to 35 million dollars between 1980 and 2000. However, in order to
restart the industry, the next six U.S. reactors will receive subsidies equal
to those of renewables and, in the event of cost overruns due to delays, at
least partial compensation for the overruns (see Nuclear Power 2010 Program).
According to the DOE, insurance for nuclear or
radiological incidents in the U.S., is subsidized by the Price-Anderson
Nuclear Industries Indemnity Act.[ In July 2005, Congress extended this Act
to newer facilities. In the UK, the Nuclear Installations Act of 1965 governs
liability for nuclear damage for which a UK nuclear licensee is responsible.
The Vienna Convention on Civil Liability for Nuclear Damage puts in place an
international framework for nuclear liability.
Other economic issues
Nuclear Power plants tend to be most competitive in areas
where other fuel resources are not readily available — France, most notably,
has almost no native supplies of fossil fuels. The province of Ontario,
Canada is already using all of its best sites for hydroelectric power, and
has minimal supplies of fossil fuels, so a number of nuclear plants have been
built there. India is also building new nuclear plants to supplement its vast
coal reserves and coal-generated electricity. Conversely, in the United
Kingdom, according to the government's Department Of Trade And Industry, no
further nuclear power stations are to be built, due to the high cost per unit
of nuclear power compared to fossil fuels. However, the British government's
chief scientific advisor David King reports that building one more generation
of nuclear power plants may be necessary. China tops the list of planned new
plants, due to its rapidly expanding economy and fervent construction in many
types of energy projects.
Most new gas-fired plants are intended for peak supply.
The larger nuclear and coal plants cannot quickly adjust their instantaneous
power production, and are generally intended for baseline supply. The market
price for baseline power has not increased as rapidly as that for peak
demand. Some new experimental reactors, notably pebble bed modular reactors,
are specifically designed for peaking power.
Any effort to construct a new nuclear facility around the
world, whether an older design or a newer experimental design, must deal with
NIMBY objections. Given the high profile of both the Three Mile Island and Chernobyl
accidents, few municipalities welcome a new nuclear reactor, processing
plant, transportation route, or experimental nuclear burial ground within
their borders, and many have issued local ordinances prohibiting the
development of nuclear power. However, a few U.S. areas with nuclear units
are campaigning for more (see Nuclear Power 2010 Program). The media,
however, should be held accountable for sensationalism and one-sided
reporting concerning the nuclear power industry. Using the Russian-designed Chernobyl
reactor in arguments against US-built nuclear power plants is a favorite
tactic of the anti-power camp as well. The fact is that even the US nuclear
plants built in the 1960s are a safer design than Chernobyl. But using a
design inferior to even our own 60-year-old designs in arguments against todays
generation of nuclear power plants is an argument doomed to fail. Most people
will react as expected when asked if a Chernobyl-like reactor should be in
their back yard. If given the choice between a modular pebble bed reactor
producing clean and reliable electricity and a smoke-belching and
ecologically devastating coal- or gas-fired plant most people should make the
intelligent decision. Fear-mongering and doom-and-gloom predictions that have
never come true have sold a lot of newspapers and raised ratings on many a
nightly news program but what Americans want now and for their children is a
clean and reliable source of electricity that will not pass along an
ecological disaster to future generations.
Current nuclear reactors return around 40-60 times the
invested energy when using life cycle analysis. This is better than coal,
natural gas, and current renewables except hydropower.
Nuclear power, coal, and wind power are currently the only
realistic large scale energy sources that would be able to replace oil and natural
gas after a peak in global oil and gas production has been reached[citation
needed] (see peak oil). However, The Rocky Mountain Institute claims that in
the U.S. increases in transportation efficiency and stronger, lighter cars
would replace most oil usage with what it calls negawatts. Biofuels can then
substitute for a significant portion of the remaining oil use. Efficiency,
insulation, solar thermal, and solar photovoltaic technologies can substitute
for most natural gas usage after a peak in production. Most transportation
experts rightly label bio-fuel claims as pie-in-the-sky as the amount of
acreage needed to grow enough fuel for our automobiles even at today's demand
would take most of the usable farmland in the country.
Nuclear proponents often assert that renewable sources of
power have not solved problems like intermittent output, high costs, and
diffuse output which requires the use of large surface areas and much
construction material and which increases distribution losses. For example,
studies in Britain have shown that increasing wind power production
contribution to 20% of all energy production, without costly pumped Hydro or
electrolysis/fuel cell storage, would only reduce coal or nuclear power plant
capacity by 6.7% (from 59 to 55 GWe) since they must remain as backup in the
absence of power storage. Nuclear proponents often claim that increasing the
contribution of intermittent energy sources above that is not possible with
current technology. Some renewable energy sources, such as solar, overlap
well with peak electricial production and reduce the need of spare generating
capacity. Future applications that use electricity when it is available (e.g.
for pressurizing water systems, desalination, or hydrogen generation) would
help to reduce the spare generation capacity required by both nuclear and
renewable energy sources.
Concerns about nuclear power
Accident or attack
The Ignalina nuclear power plant in Lithuania contains two RBMK reactors. Because of the safety flaws of the design, the closure of the plant was a condition of Lithuania's entry into the EU. The first of the two reactors was closed down in 2004 and the second is scheduled for shutdown by 2009. (Photograph courtesy of the Nordic Council).Opponents argue that a major disadvantage of the use of nuclear reactors is the threat of a nuclear accident or terrorist attack and the possible resulting exposure to radiation.
Proponents argue that the potential for a meltdown in well-designed reactors is very small due to the care taken in designing adequate safety systems, and that the nuclear industry has much better statistics regarding humans deaths from occupational accidents than coal or hydropower. While the Chernobyl accident caused great negative health, economic, environmental and psychological effects in a widespread area, the accident at Chernobyl was caused by a combination of the faulty RBMK reactor design, the lack of a properly designed containment building, poorly trained operators, and a non-existent safety culture. The RBMK design, unlike nearly all designs used in the Western world, featured a positive void coefficient, meaning that a malfunction could result in ever-increasing generation of heat and radiation until the reactor was breached. Even at Three Mile Island, the most severe civilian nuclear accident in the non-Soviet world, the reactor vessel and containment building were never breached, even though it had suffered a core meltdown, so that very little radiation (well below natural background radiation levels) was released into the environment.
Design changes are being pursued in the hope of lessening some of the risks of fission reactors; in particular, automated and passively safe designs are being pursued. Fusion reactors which may come to exist in the future theoretically have little risk since the fuel contained in the reaction chamber is only enough to sustain the reaction for about a minute, whereas a fission reactor contains about a year's supply of fuel. Subcritical reactors never have a self sustained nuclear chain reaction.
Opponents of nuclear power express concerns that nuclear waste is not well protected, and that it can be released in the event of terrorist attack, 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, sometimes leading to the guarding of nuclear shipments by thousands of police. Other energy sources, such as hydropower plants and LNG carriers, are more vulnerable to accidents and attacks. Proponents of nuclear power contend, however, that nuclear waste is already well protected, and state their argument that there has been no accident involving any form of nuclear waste from a civilian program worldwide. In addition, they 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. 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.
According to the Nuclear Regulatory Commission, 20 American states have requested stocks of potassium iodide which the NRC suggests should be available for those living within 10 miles of a nuclear power plant in the unlikely event of a severe accident.
Health effects on populations
Most of the 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, after doing a large-scale study which evaluated the mortality rates from 16 types of cancer, no increased incidence of cancer mortality was found for people living near 62 nuclear installations in the United States. The study also showed no increase in the incidence of childhood leukemia mortality in the study of surrounding counties after the 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.
Aside from the immediate effects of the Chernobyl accident (see above), there is continuing impact from soils containing radioactivity in Ukraine and Belarus. For this reason a Zone of alienation was established around the Chernobyl plant.
In March, 2006, safety reviews found that several nuclear plants in the United States have been leaking water contaminated with tritium into the ground. (The discharges were intended to go through discharge pipes into rivers, at levels which would be below regulatory limits. However, by leaking into the ground, very low levels of tritium reached drinking water supplies.) The attorney general of Illinois announced that she was filing a lawsuit against Exelon because of six such leaks, demanding that the utility provide substitute water supplies to residents although no well outside company property shows levels that exceed drinking water standards. According to the NRC, "The inspection determined that public health and safety has not been adversely affected and the dose consequence to the public that can be attributed to current onsite conditions is negligible with respect to NRC regulatory limits." However, the chairman of the Nuclear Regulatory Commission, said, "They're going to have to fix it."
Opponents of nuclear power point out that nuclear technology is often dual-use, and much of the same materials and knowledge used in a civilian nuclear program can be used to develop nuclear weapons. This concern is known as nuclear proliferation and is a major reactor design criterion.
The military and civil purposes for nuclear energy are intertwined in most countries with nuclear capabilities. 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."
The enriched uranium used in most nuclear reactors is not concentrated enough to build a bomb. Most nuclear reactors run on 4% enriched uranium; Little Boy used 80% enriched uranium; while lower enrichment levels could be used, the minimum bomb size would rapidly become infeasibly large as the level was decreased. However, the same plants and technology used to enrich uranium for power generation can be used to make the highly enriched uranium needed to build a bomb.
In addition, the plutonium produced in power reactors, if concentrated through reprocessing, can be used for a bomb. While the plutonium resulting from normal reactor fuelling cycles is less than ideal for weapons use because of the concentration of Pu-240, a usable weapon can be produced from it. If the reactor is operated on very short fuelling cycles, bomb-grade plutonium can be produced. However, such operation would be virtually impossible to camouflage in many reactor designs, as the frequent shutdowns for refuelling would be obvious, for instance in satellite photographs.
It is widely believed that the nuclear programs of India and Pakistan used CANDU reactors to produce fissionable materials for their weapons; however, this is not entirely accurate. Both Canada (by supplying the 40 MW research reactor) and the United States (by supplying 21 tons of heavy water) supplied India with the technology necessary to create a nuclear weapons programme, dubbed CIRUS (Canada-India Reactor, United States). Because international policies did not dictate usage of nuclear technology transfers, India was able to use the technology to create a nuclear weapon. Pakistan is believed to have produced the material for its weapons from an indigenous enrichment program.
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). South
Africa has since signed the NPT, and now holds the distinction of being the
only known state to have indigenously produced nuclear weapons, and then
verifiably dismantled them. 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, including Iran and North Korea. Certain types of
reactors are more conducive to producing nuclear weapons materials than
others, 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.
New technology, like SSTAR, may lessen the risk of nuclear
proliferation by providing sealed reactors with a limited self-contained fuel
supply and with restrictions against tampering.
One possible obstacle for expanding the use of nuclear
power might be a limited supply of uranium ore, without which it would become
necessary to build and operate breeder reactors. However, at current usage
there is sufficient uranium for an extended period — "In summary, the
actual recoverable uranium supply is likely to be enough to last several
hundred (up to 1000) years, even using standard reactors." Breeder
reactors have been banned in the U.S. since President Jimmy Carter's
administration prohibited reprocessing because of what it regarded as the
unacceptable risk of proliferation of weapons-grade materials.
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 since it seems that democracies refrain from war against each
other (See the democratic peace theory).
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
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 proliferation infeasible, while making
nuclear power available to developing countries.
Non-radioactive water vapour is the significant operating
emission from nuclear power plants. Fission produces gases such as
iodine-131 or Xenon-133. These primarily remain within the fuel rods, but
with some postulated fuel failure, small amounts of the gases can be released
in to the reactor coolant. The chemical control systems isolate the
radioactive gases which have to be stored on-site for several half-lives
until they have decayed to safe levels. Iodine-131 and Xenon-133 have halflives
of 8.0 and 5.2 days respectively, and thus have to be stored for a few months
to decay to safe levels.
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).
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).
Several life cycle analyses show similar emissions per
kilowatt-hour from nuclear power and from renewables such as wind power.
According to one life cycle study by van Leeuwen and Smith from 2001–2005,
carbon dioxide emissions from nuclear power per kilowatt hour could range
from 20% to 120% of those for natural gas-fired power stations depending on
the availability of high grade ores. The study was critiqued by World Nuclear
Association (WNA), rebutted in 2003, then dismissed by the WNA in 2006 based
on its own life-cycle-energy calculation (with comparisons).
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% decrease in total UK CO2 emissions by
2035. This can be compared to the country's goal to reduce greenhouse gas
emissions by 60 % by 2050. As of 2006, the UK government was to publish its
official findings later in the year.
Waste heat in water systems
Nuclear reactors require cooling, typically with water (sometimes indirectly). The process of using water to extract energy from a heat source requires a cooling source, this process is described by the Rankine cycle. There is a limitation on the amount of heat that can be converted into energy through the Rankine Cycle. The excess heat must be rejected as waste heat, this is where the cooling water is required. Rivers are the most common source of cooling water, as well as the destination for waste heat. The temperature of exhaust water must be regulated to avoid killing fish; long-term impact of hotter-than-natural water on ecosystems is an environmental concern. In most new facilites, this problem is solved by using cooling towers. This is true of all traditional power plant designs, including coal, oil, and natural gas plants, which also rely on the Rankine cycle to produce their energy. All four types of plants differ in their heat source, be it nuclear fission or burning fossil fuels.
The need to regulate exhaust temperature can limit
generation capacity. On extremely hot days, which is when demand can be at
its highest, the capacity of a nuclear plant may go down because the incoming
water is warmer to begin with and is thus less effective as a coolant, per
unit volume. This was a significant factor during the European heat Wave of
2003. Engineers consider this in making improved power plant
designs because increased cooling capacity will increase capital costs. The
global increase in average temperature has required some plants in the
southeast United States to revise their technical specifications to allow
operation with their cooling water sources at higher temperatures.[citation
List of atomic energy groups
American Nuclear Society (United States)
Atomic Energy of Canada Limited (Canada)
Department of Energy (United States)
Egyptian Atomic Energy Authority
Électricité de France (France)
Indian Atomic Energy Commission (India)
International Atomic Energy Agency (IAEA)
National Atomic Energy Commission - CNEA (Argentina)
Nuclear Energy Institute (United States)
Pakistan Atomic Energy Commission (Pakistan)
United Kingdom Atomic Energy Authority (United Kingdom)
World Nuclear Association (International)
See also: Related Topics @ Wikipedia
Wikimedia Commons has media related to:
Atoms for Peace
Global Nuclear Energy Partnership
Ionizing radiation for a table of radiation exposures
List of countries with nuclear weapons
List of civilian nuclear accidents
List of nuclear reactors
Nuclear power controversy
Nuclear power phase-out
Spent nuclear fuel shipping cask
Original Wikipedia article here - http://en.wikipedia.org/wiki/Nuclear_power
End of Wikipedia content
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