Nuclear power

This article is about power derived from nuclear reactions. For countries that possess nuclear weapons see: Nuclear powers .

Life cycle

A Nuclear Reactor is only a small part of the lifecycle 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.

Related Topics:
Yellowcake - Uranium hexafluoride - Enriched - Cooling pond

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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 http://www.world-nuclear.org/info/inf75.htm http://www.americanenergyindependence.com/uranium.html. Also, extraction from seawater http://www.ans.org/pubs/journals/nt/va-144-2-274-278 or granite is possible. 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 http://www.world-nuclear.org/info/inf62.htm.

Related Topics:
Uranium - Thorium

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Current light water reactors make relatively inefficient use of nuclear fuel, leading to energy waste. More efficient reactor designs or nuclear reprocessing http://www.world-nuclear.org/info/inf04.htm 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 http://www-formal.stanford.edu/jmc/progress/cohen.html. Breeder technology has been used in several reactors http://www.world-nuclear.org/info/inf08.htm.

Related Topics:
Light water reactors - Nuclear reprocessing - Uranium-235 - Fast breeder reactors - Uranium-238

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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 ouput 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. http://www.fusie-energie.nl/artikelen/ongena.pdf

Related Topics:
Fusion reactor - Deuterium - Isotope - Hydrogen - Lithium

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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. Reprocessing of civilian nuclear fuel is not done in the United States due to proliferation concerns.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Solid 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-lifes of the radioactive isotopes in the waste. Also, during reactor operation, the reaction chamber is bombarded with high-energy neutrons - this makes the decomissioning 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 http://www.world-nuclear.org/education/ne/ne5.htm.

Related Topics:
Nuclear waste - Half-life - Isotope

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.http://beheer.oprit.rug.nl/deenen/ 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.

Related Topics:
As of 2003 - United States - United States Environmental Protection Agency

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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. 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.

Related Topics:
Yucca Mountain - Nuclear fuel cycle

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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 decomissioning 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 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.

Related Topics:
Nuclear Regulatory Commission - 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.

Related Topics:
Depleted uranium - Lead

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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 http://www.world-nuclear.org/info/inf35.htm. 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.

Related Topics:
Nuclear reprocessing - Fast breeder reactor - Subcritical reactor

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In countries with nuclear power, radioactive wastes comprise less than 1% of total industrial toxic wastes (which remains hazardous indefinitely) http://www.world-nuclear.org/info/inf04.htm.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~