Nuclear power

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A nuclear power station. Non-radioactive water vapor rises from the hyperboloid shaped cooling towers. The nuclear reactors are inside the cylindrical containment buildings.

Nuclear power is the use of nuclear reactions to generate power, usually electrical, such as in an atomic battery or a nuclear power plant.

Nuclear power plants generate power by nuclear fission reactions which occur when sufficient amounts of uranium-235 and/or plutonium are confined to a small space, often in the presence of a neutron moderator. The reaction produces heat which is converted to kinetic energy by means of a steam turbine and then a generator for electricity production. Nuclear power provides about 20% of the U.S.'s electricity [1], 17% of the world's and 7% of total global energy. An international effort into the use of nuclear fusion for power is ongoing, but not expected to be available in commercially viable form for several decades.

After a period of decline following the 1979 Three Mile Island accident and the 1986 incident at Chernobyl, there is currently a renewed interest in nuclear energy because on the one hand nuclear energy produces electricity without requiring fossil fuels or releasing green house gasses (except for the mining veicles and coal-fired plants used to process the fuel); on the other, it produces long term nuclear waste, the method of disposal of which has not come to consensus; on the one hand nuclear power resulted in the Chernobyl disaster and three mile island; On the other, far more people die in coal mines each year than uranium mines and nuclear plants.

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 could in some countries lead to the proliferation of nuclear weapons. Proponents, including some national governments, claim that these risks are small and can be lessened with new technology. They further claim that France and all of the industrialised economies of Asia [2] see nuclear power as a key economic strategy, that the safety record is already good when compared to other energy forms, that it releases much less radioactive waste than coal power, and that nuclear power is a sustainable energy source. Many environmental groups claim 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.

History

Origins

The first successful experiment with nuclear fission was conducted in 1938 in Berlin by the German physicists Otto Hahn, Lise Meitner and Fritz Strassman.

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 by Enrico Fermi on December 2nd,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". [3]

A December 1953 speech by President Dwight Eisenhower, "Atoms for Peace", set the US on a course of strong government support for the international use of nuclear power.

Early years

On June 27, 1954, the world's first nuclear power plant that generated electricity for commercial use was officially connected to the Soviet power grid at Obninsk, USSR. The reactor was graphite moderated, water cooled and had a capacity of 5 megawatts (MW). The second reactor for commercial purposes (1956) was Calder Hall in Sellafield, England, a gas-cooled Magnox reactor with an initial capacity of 45 MW (later 196 MW). The Shippingport Reactor (Pennsylvania, 1957), a pressurised-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 US Nuclear Regulatory Commission) famously declared that nuclear power would be "too cheap to meter" [4] 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).

Thanks to the presence of the nearby Bettis Laboratory and the Shippingport power plant, Pittsburgh, Pennsylvania became the world's first nuclear powered city in 1960.

Development

Installed nuclear capacity initially rose relatively quickly, rising from less than 1 gigawatt (GW) in 1960 to 100GW in the late 1970s, and 300GW in the late 1980s. Since the late 1980s capacity has risen much more slowly, reaching 366GW in 2005, primarily due to Chinese expansion of nuclear power. Between around 1970 and 1990, more than 50GW of capacity was under construction (peaking at over 150GW in the late 70s and early 80s) - currently around 25GW of capacity is planned. More than two-thirds of all nuclear plants ordered after January 1970 were eventually cancelled.[5]

Rising economic costs (related to vastly extended construction times) and falling fossil fuel prices gradually made nuclear power less economically competitive during the 1970s and 1980s. In the 1980s (US) and 1990s (Europe), electricity liberalization also played a part in increasing the financial risks of investing in nuclear power.

A popular movement against nuclear power also gained strength in the World, based on the fear of a possible nuclear accident and on fears of latent radiation, and on the opposition to nuclear waste production, transport and final storage. Those risks on the citizens health and safety, the 1979 accident at Three Mile Island and the 1986 Chernobyl accident 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. The Brookings institution suggests that nuclear power may have been phased out for primarily economic reasons rather than fears of accidents. The use of nuclear power for electricity generation have been suspected of encouraging nuclear proliferation in some countries like recently in Iran.

Future plans

The countries which shut down nuclear power plants have to find alternatives for energy generation. Therefore, the discussion of a future for nuclear energy is intertwined with a discussion of renewable energy development. The most discussed alternatives to nuclear power include hydroelectricity, fossil energy, solar energy, and biomass (see also alternative energy).

However nuclear power still continued in many other countries, notably France, Japan, the former USSR and recently China. The 1600MW EPR reactor being built in Olkiluoto, Finland, will be the largest in the world. The U.S. is planning new plants (see Current and Planned Use below).

Current and planned use

In 2005, there were 441 commercial nuclear generating units throughout the world, with a total capacity of about 368 gigawatts.[6] 111 reactors (36GW) have been shut down.[7] 80% of reactors (and of generating capacity) are more than 15 years old.[8]

In 2004 in the United States, there were 104 (69 pressurized water reactors and 35 boiling water reactors) commercial nuclear generating units licensed to operate, producing a total of 97,400 megawatts (electric), which is approximately 20 percent of the nation's total electric energy consumption. The United States is the world's largest supplier of commercial nuclear power. Future development of nuclear power in the U.S. (see the Nuclear Power 2010 Program) was enabled by the Energy Policy Act of 2005 [9]. As of 2005, no nuclear plant had been ordered without subsequent cancellation for over twenty years, thus the desire for programs to promote new construction. However, on September 22, 2005 it was announced that two sites in the U.S. had been selected to receive new power reactors (exclusive of the new power reactor scheduled for INL) - see Nuclear Power 2010 Program.

In France, as of 2005, 78% of all billed electrical energy was generated by 58 nuclear reactors, the highest share in the world. Some sources cite Lithuania as the world's most nuclear-dependant nation, generating 85% of its power from nuclear reactors. However, this is mostly a testament to the country's low power demand, as Lithuania runs only a single 1500MWe RBMK-2 at its Ignalina Nuclear Power Plant.[10]

Argentina, Brazil, Canada, China, Finland, India, Iran, Japan, North Korea, Pakistan, Romania, Russia, South Korea, Taiwan, Ukraine, and the U.S. are currently planning or building new nuclear reactors or reopening old ones. Bulgaria, Czech Republic, Egypt, France, Indonesia, Israel, Slovakia, South Africa, Turkey, United Kingdom and Vietnam , are considering doing this. Armenia, Belgium, Germany, Hungary, Lithuania, Mexico, Netherlands, Slovenia, Spain, Sweden, and Switzerland have nuclear reactors but currently no advanced proposals for expansion. [11] [12][13]. Belgium, Germany, Italy, Spain and Sweden have decided on a nuclear power phase-out.

According to the EIA and the IEA, nuclear power is projected to have a slightly declining 5-10% share of world energy production until 2025, assuming that fossil fuel production can continue to expand rapidly (which is controversial). See Future energy development.

Reactor Types

Current Technology

There are two types of nuclear power sources in current use:

For more details on this topic, see Nuclear power plant.

Experimental Technologies

A number of other designs for nuclear power generation are the subject of active research and may be used for practical power generation in the future. A number of advanced nuclear reactor designs could also make critical fission reactors much cleaner and safer.

Nuclear power primarily produces concentrated heat. This can be converted to electricity and this currently constitutes a small but significant percentage of worldwide electricity generation. The heat can also be converted to mechanical work and this is the power source for many large military ocean going vessels (and a few commercial or government vessels). Other possible uses for the heat is in chemical processes, such as in the production of hydrogen, desalination [16], or direct heating of houses, especially by the massive amount of low grade waste heat generated by power plants.

Life cycle

Nuclear fuel cycle begins when uranium is mined, enriched and manufactured to 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 a small 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. At the reprocessing facility, 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 cooling pond 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.

Fuel resources

At the present rate of use, there are 50 years left of low-cost known uranium reserves - however, given that the cost of fuel is a minor cost factor for fission power, more expensive lower-grade sources of uranium could be used in the future [17] [18]. Other ideas include extraction from seawater and granite - although there is controversy on this issue. Arguments for and against these ideas can be found at [19], [20] (for), and [21] (against).

Another alternative would be to use thorium as fission fuel in breeder reactors - thorium is three times more abundant in the Earth crust than uranium [22].

Current light water reactors make relatively inefficient use of nuclear fuel, leading to energy waste. More efficient reactor designs or nuclear reprocessing [23] 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 anywhere from 10,000 to five billion years worth of Uranium-238 for use in these power plants [24]. Breeder technology has been used in several reactors [25]. Currently (December 2005), the only breeder reactor producing power is BN-600 [26] 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.

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 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. [27]

Reprocessing

For more details on this topic, see Nuclear reprocessing

Reprocessing can recover up to 95% of the remaining uranium and plutonium in spent nuclear fuel, putting it into new mixed oxide fuel. Reprocessing of civilian fuel from power reactors is currently done on large scale in England, 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. [28] Reprocessing of civilian nuclear fuel is not done in the United States due to proliferation concerns.

Solid waste

For more details on this topic, see Nuclear waste.

Nuclear power produces spent fuel, a unique solid waste problem. Because spent nuclear fuel is radioactive, extra care and forethought are given to facilitate their safe storage (see nuclear waste). The waste from highly radioactive spent fuel needs to be handled with great care and forethought due to the long half-lives of the radioactive isotopes in the waste. Also, during reactor operation, the reaction chamber is bombarded with high-energy neutrons - this makes the decommissioning process more expensive when the reactor reaches the end of its life cycle (40 to 60 years for many current designs). However, spent nuclear fuel becomes less radioactive over time - after 40 years 99.9% of radiation disappears [29].

Spent fuel 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. It is possible through reprocessing to separate out the actinides and use them again for fuel, but this often requires special fast spectrum reactors, which produce a reduction in long term radioactivity within the remaining waste. In any case, 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 in the most optimistic scenarios (complete consumption of all actinides, and using fast spectrum reactors to destroy some of the long-lived non-actinides as well), the waste must be segregated from the environment for at least several hundred years, and therefore this is properly categorized as a long term problem.

The average nuclear power station produces 20-30 tonnes of spent fuel each year.[30] As of 2003, the United States had accumulated about 49,000 metric tons of spent nuclear fuel from nuclear reactors. Unlike other countries, U.S. policy forbids recycling of used fuel and it is all treated as waste. After 10,000 years of radioactive decay, according to United States Environmental Protection Agency standards, the spent nuclear fuel will no longer pose a threat to public health and safety.

The safe storage and disposal of nuclear waste is a difficult challenge. Because of potential harm from radiation, spent nuclear fuel must be stored in shielded basins of water, or in dry storage vaults or dry cask storage until its radioactivity decreases naturally ("decays") to safe levels. This can take days or thousands of years, depending on the type of fuel. Most waste is currently stored in temporary storage sites, requiring constant maintenance, while suitable permanent disposal methods are discussed. Underground storage at Yucca Mountain in U.S. has been proposed as permanent storage. See the article on the nuclear fuel cycle for more information.

The nuclear industry 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. Much low-level waste releases very low levels of radioactivity and is essentially 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. 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 radioactive ash due to concentrating naturally occurring radioactive material in the coal.

In addition, the nuclear industry fuel cycle produces many tons of depleted uranium (uranium from which the easily fissile U235 element has been removed, leaving behind only U238). This material is much more concentrated than natural uranium ores, and must be disposed of. U238 is a very tough metal with several commercial uses, for example aircraft production and radiation shielding. In particular, depleted uranium is much sought after for making bullets and armor, as it has higher density than even lead. There has been some concern that this may be causing health problems in some groups exposed to this material excessively, such as tank crews.

The amounts of waste can be reduced in several ways. Both nuclear reprocessing and fast breeder reactors can reduce the amounts of waste and increase the amount of energy gained per fuel unit. Subcritical reactors or fusion reactors could greatly reduce the time the waste has to be stored [31]. Subcritical reactors may also be able to do the same to already existing waste. 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 valuable fuel in the future, particularly if it is not reprocessed, as in the U.S.

In countries with nuclear power, radioactive wastes comprise less than 1% of total industrial toxic wastes (which remains hazardous indefinitely) [32].

Economy

Opponents of nuclear power claim that any of the environmental benefits are outweighed by safety compromises and by the costs related to construction and operation of nuclear power plants, including costs for spent-fuel disposition and plant retirement. Proponents of nuclear power state 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 £0.22-0.26/kWh and coal gasification was £0.32/kWh. When carbon tax was added (up to £0.25) coal came close to onshore wind (including back-up power) at £0.54/kWh - offshore wind is £0.72/kWh. Nuclear power remained at £0.23/kWh either way, as it produces negligible amounts of CO₂. Nuclear figures included decommissioning costs. [33] (see also [34]). (See also the MIT report.)

Capital costs

Generally, a single nuclear power plant is significantly more expensive to build than a single steam-based coal-fired plant. A coal plant is itself more expensive to build than a single natural gas-fired combined-cycle plant, making it possible for a utility to build additional natural gas plants in smaller increments, and in areas of low power consumption. (However, coal is significantly more expensive than nuclear fuel, and natural gas significantly more expensive than coal - thus natural gas-generated power is the most expensive.)

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. Building gas-fired or coal-fired plants has not had these problems. Because a power plant does not yield profits during construction, longer construction times translated 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 less 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 [35].

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.

Operating costs

In the U.S. coal and nuclear power plants must operate more cheaply than natural gas plants to be built. In general, coal and nuclear plants have the same operating costs (operations and maintenance plus fuel costs). However, nuclear and coal differ in the source of those costs. Nuclear has lower fuel costs but higher operating and maintenance costs than coal. In recent times in the United States these operating costs have not been low enough for nuclear to repay its high investment costs. Thus new nuclear reactors have not been built in the United States. 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. These numbers exclude capacity expansions at existing coal and nuclear units.

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, which also have the same operating costs. 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 nuclear industry has been the reluctance of the U.S. government to tax carbon emissions which causes global warming. Only when the negative externalities of coal and gas consumption in the form of carbon emissions is taxed will nuclear industry become competitive. The U.S. government has been unwilling to join Kyoto protocol which would have ensured that the free market would dictate efficient quantities of nuclear power production but has instead been willing to ensure that the Government decides behind closed doors in an untransparent manner how subsidies are doled out.

Subsidies

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, like tax benefits and not having to pay for their pollution [36]. Renewables receive large direct production subsidies and tax breaks in many nations [37].

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 2179 to 35 million dollars between 1980 to 2000 [38] - 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 US, is subsidized [39] 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 no other resources are readily av