Nuclear power is the energy generated from nuclear reactions or decay of an atom nucleus. Introduced as a post-war olive branch by President Eisenhower in his Atoms for Peace Campaign, atomic energy held out the promise of electricity abundant enough to share and "too cheap to meter". Unfortunately the reality of nuclear energy includes a series of preventable catastrophies which have underscored the unique health consequences of nuclear incidents. Today, its continued use and expansion is a matter of heated controversy for a variety of stated reasons including: the challenge of securing radioactive waste for the thousands of years during which it remains dangerous, the uninsurable risk of severe radioactive contamination caused by willful negligence, and the gateway effect of nuclear energy on the proliferation of nuclear weapons. Because nuclear power is a demonstrated technology, it could be rapidly built out in the future if fossil fuels are depleted or restricted for environmental reasons.

History

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 in 1943, and reactors based on his research were used to produce the plutonium necessary for two of the nuclear weapons (the "Trinity" device and 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 usage for civilian electricity generation.

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 only 5 MW. The second reactor for commercial uses was Calder Hall in Sellafield, England with a capacity of 45 MW. The Shippingport Reactor (Pennsylvania) was the first commercial nuclear generator to become operational in the United States.

Falling fossil fuel prices gradually made nuclear power less economically competitive during the 1980s. A popular movement against nuclear power also gained strength in the Western world, based on the fear of a possible accident and on fears of latent radiation. This and the accident at Three Mile Island in 1979, effectively stopped new plant construction in many countries. However it still continued strongly in many other countries, notably France and the former USSR.

In 1986, a large accident at a nuclear power plant at Chernobyl, Ukraine, exposed much of Europe to nuclear fallout and greatly heightened European concerns about nuclear power and nuclear safety.

Developing countries like India and China are rapidly increasing their nuclear energy use [1][2].

Reactor Types

Current Technology

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

1. 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.

2. 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.

Future 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.

1. Subcritical reactors are designed to be safer and more stable, but pose a number of engineering and economic difficulties.

2. Controlled nuclear fusion could in principle be used in fusion power plants to produce safer, cleaner power, but significant scientific and technical obstacles remain. Despite research having started in the 1950s, no commercial fusion reactor is expected before 2050 [3]. The ITER project is currently the leading the effort to commercialize fusion power.

3. A number of advanced nuclear reactor designs could also make critical fission reactors much cleaner and safer. Typical new reactor designs have a construction time of three to four years.[4].

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, like in the production of hydrogen, desalination, or direct heating of houses.

Uranium and thorium resources

At the present use rate, there are 50 years left of low cost known uranium reserves [5]. 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. For example: extraction from seawater [6] or granite. Another alternative would be to use thorium as fission fuel. Thorium is three times more abundant in the Earth crust than uranium [7].

Current light water reactors burn the nuclear fuel poorly, leading to energy waste. Nuclear reprocessing [8] or burning the fuel better using different reactor designs would reduce the amount of waste material generated and allow better use 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 [9]. Breeder technology has been used in several reactors [10].

Economy

Critics of nuclear power assert 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 maintain 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.

In the U.S, 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. Although the cost per megawatt for a nuclear power plant is comparable to a coal-fired plant and less than a natural gas plant, the smallest nuclear power plant that can be built is much larger than the smallest natural gas power plant, making it possible for a utility to build natural gas plants in much smaller increments.

In the U.S., licensing, inspection and certification delays add large amounts of time and cost to the construction of a nuclear plant. These delays and costs are not present when building either gas-fired or coal-fired plants. Because a power plant does not earn money 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 since been standardized, to make construction of newer and inherently safer designs more attractive to utilities and their investors.

In the U.S., these charges require that coal and nuclear power plants must operate more cheaply than natural gas plants in order 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.

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 have no visible advantage in operating costs over coal plants. The burden of operating costs for nuclear power plants is also greater. Operation and maintenance costs are particularly important simply because they are a large portion of nuclear operating costs.

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, but no type license has ever been issued by a U.S. nuclear regulatory agency.

Given the financial disadvantages of nuclear power in the U.S., it is understandable that the nuclear industry also has sought to find additional benefits to using nuclear power. Because coal-fired plants produce more airborne emissions, clearly the price differential accepted between nuclear and coal based power would be greater than the acceptable difference between nuclear power and natural gas.

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 demand for baseline power has not increased as rapidly as the peak demand. Some new experimental reactors, notably pebble bed modular reactors, are specifically designed for peaking power.

Finally, any company seeking to construct a nuclear reactor around the world (but most acutely in the US) must deal with NIMBY issues. Given the high profile of both Three Mile Island and Chernobyl, few municipalities would welcome a new nuclear reactor within their borders, and many have issued local ordinances prohibiting the development of nuclear power.

In an attempt to encourage development of nuclear power, the United States Department of Energy has offered interested parties the opportunity to introduce France's model for licensing and to share 50% of the construction expenses. Several applications were made but the project is still in its infancy.

Nuclear Power plants usually tend to be most competitive in areas where no other resources are readily available. For example, 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. 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. [11]

Risks

The risks of nuclear power include the long term problems of storing radioactive waste, the potential for severe radioactive contamination by an accident, and the possibility that its use will lead to the proliferation of nuclear weapons. As a result nuclear power is the subject of significant opposition. Organisations such as Greenpeace and Friends Of The Earth actively campaign against the continued use of nuclear power.

The dangers of nuclear power must also be weighed against the dangers of other methods of electricity generation. See environmental concerns with electricity generation for discussion of this issue.

Proponents argue that the risks are small and that fear has been the single largest obstacle to the widespread use of nuclear power. They argue that nuclear power is currently the only realistic alternative large scale energy source that would be able to replace oil and natural gas after a peak in global oil and gas production has been reached (see peak oil). The only other possible solution is coal which currently contributes significantly to problems like global warming, acid rain, various diseases due to airborne pollution, and storage of large amounts of ash. Proponents of nuclear power also claim that unlike coal, nuclear power produces little airborne pollution, does not directly contribute to global warming, and pollutes to the same degree as many renewable energy sources. Future technology may both increase the efficiency and safety of alternative energy sources, including nuclear, and make them more environmentally friendly.

Accident or attack

A major disadvantage of the use of nuclear reactors is the perceived threat of an accident or terrorist attack and resulting exposure to radiation. Proponents contend that the potential for a meltdown, as in Chernobyl, is very small due to the care taken in designing adequate safety systems, and that the nuclear industry overall has quite a good safety record compared to other industries (Safety page). The accident at Chernobyl is thought to have been caused by a combination of a faulty reactor design, poorly trained operators, and a non-existent safety culture. Even in an accident such as Three Mile Island, the containment vessels were never breached, so that very little radiation was released into the environment. Historically, coal and hydropower power generation has both been the cause of more deaths per energy unit produced than nuclear power generation. Research is being done to lessen the risks by developing automated and passively safe reactors.

Opponents of nuclear power, claim that nuclear waste is not well protected, and that it can be released in the event of terrorist attack. Other energy sources like, hydropower plants and liquified natural gas tankers, are also vulnerable to accidents attacks. Proponents of nuclear power contend, however, that nuclear waste is 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 (see Resistance to terrorist attack). Spent fuel is usually housed inside reactor containment (see [Fuel Storage).

Airborne pollution

Proponents of nuclear power point out that all power sources, including renewables, contribute to global warming, for example when mining and refining raw materials. However, most life cycle analysis shows that nuclear power contribution is about equal to that of many renewables and is much less than that from fossil fuels. [12].

Fission reactors produce gases such as iodine-131 or krypton-85 which have to be stored on-site for several half-lives until they have decayed to levels officially regarded as safe. Proponents point out that the radioactive contamination released from a nuclear reactor under normal circumstances is less than the radioactive contamination from the waste of a coal-fired plant.

Health effect on population near nuclear power plants

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 US, Canada, and Europe have found no evidence of any increase in cancer mortality among people living near nuclear facilities. For example, in 1990, the National Cancer Institute (NCI) of the National Institutes of Health announced that a large-scale study, which evaluated mortality from 16 types of cancer, found no increased incidence of cancer mortality for people living near 62 nuclear installations in the United States. The study showed no increase in the incidence of childhood leukemia mortality in the study of surrounding counties after start-up of the nuclear facilities. The NCI study, the broadest of its kind ever conducted, surveyed 900,000 cancer deaths in counties near nuclear facilities.

However, in Britain there are elevated childhood leukemia levels near some industrial facilities, particularly near Sellafield, where children living locally are ten times more likely to contract the cancer. The reasons for these increases, or clusters, are unclear, but one study of those near Sellafield has ruled out any contribution from nuclear sources. Apart from anything else, the levels of radiation at these sites are orders of magnitude too low to account for the excess incidences reported. One explanation is viruses or other infectious agents being introduced into a local community by the mass movement of migrant workers. Likewise, small studies have found an increased incidence of childhood leukemia near some nuclear power plants has also been found in Germany [13] and France [14]. Nonetheless, the results of larger multi-site studies in these countries invalidate the hypothesis of an increased risk of leukaemia related to nuclear discharge. The methodology and very small samples in the studies finding an increased incidence has been criticized. [15][16][17][18].

Solid waste

Main article: 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 faciliate 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-lifes of the radioactive isotopes in the waste.

As of 2003, the United States 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 is 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. It is unclear whether this material can be safeguarded for such a long period of time.

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 containers 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. See the article on the nuclear fuel cycle for more information.

The nuclear industry produces a much greater volume of low-level radioactive waste in the form of contaminated items like clothing, hand tools, water purifier resins, and upon decomissioning the materials of which the reactor itself is built. In the United States, the NRC has repeatedly attempted to allow low-level materials to be handled as normal waste: landfilled, recycled into consumer items, etc. Much low-level waste release 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.

Nuclear power has useful additional advantages icluding the production of radioisotopes which are used in medicine and food preservation, though the demand for these products can be satisfied by a relatively small number of plants.

Proponents of nuclear power point out that the technology produces far less waste material (albeit far more hazardous) than fossil-fuel based power plants. In volume, spent fuel from nuclear power plants are roughly a million times less than waste from fossil fuel.

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 [19]. Subcritical reactors may also be able to do the same 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.

Nuclear proliferation

Main article: Nuclear proliferation

Critics of nuclear energy 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. While the enriched uranium used in most nuclear reactors is not concentrated enough to build a bomb (most nuclear reactors run on 4% enriched uranium, while a bomb requires an estimated 90% enrichment), the technology used to enrich uranium could be used to make the highly enriched uranium needed to build a bomb. In addition, breeder reactor designs such as CANDU can be used to generate plutonium for bomb making materials. It is believed that the nuclear programs of India and Pakistan used CANDU-like reactors to produce fissionable materials for their weapons.

To prevent this, safeguards on nuclear technology were imposed through the Nuclear Non-Proliferation Treaty (NPT) and monitored by the International Atomic Energy Agency (IAEA) of 1968.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.

Several states did not sign the treaty and were able to use international nuclear technology (often procured for civilian purposes) to develop nuclear weapons (India, Pakistan, Israel, and South Africa). Of those who have signed the treaty, 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.

Proponents of nuclear power argue that the risk of nuclear proliferation may be a reason to prevent nondemocratic developing nations from gaining any nuclear technology but that this is no reason for democratic developed nations to abandon their nuclear power plants. Especially since it seems that democracies never make war against each other (See the democratic peace theory). Furthermore, all power sources and technology can be used to produce and use weapons. The weapons of mass destruction used in chemical warfare and biological warfare are not dependent on nuclear power. Humans could still make war even if all technology was forbidden.

Statistics

In 2000, there were 438 commercial nuclear generating units throughout the world, with a total capacity of about 351 gigawatts.

In 2004, there were 104 (69 pressurized water reactors, 35 boiling water reactors) commercial nuclear generating units licensed to operate in the United States, 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.

The United States Navy owns and operates half of the nuclear reactors in the world. There has never been an incident in 51 years [20] of near constant naval operation of these hundreds of power plants.

In 2001, the U.S. nuclear share of electricity generation was 19%.

In France, as of 2002, 78% of all electric power was generated by nuclear reactors.

List of atomic energy groups

• American Nuclear Society (United States)
• Department of Energy (United States)
• Areva (France)
• EDF (France)
• MinAtom (Russia)
• EnergoAtom (Ukraine)
• Egyptian Atomic Energy Authority
• United Kingdom Atomic Energy Authority (UKAEA)
• EURATOM (Europe)

External Links

• World Nuclear Association
• Calendar of Nuclear Accidents
• World Information Service on Energy (WISE)

See also

• Fusion power
• Nuclear physics
• Future energy development