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Nuclear reactor

A nuclear reactor is a device in which nuclear chain reaction Nuclear chain reaction

A nuclear chain reaction occurs when on average more than one nuclear reaction [i] is caused by another ... 

s are initiated, controlled, and sustained at a steady rate . Nuclear reactors are used for many purposes. The most significant current use is for the generation of electrical power Electric power

Electric power is defined as the amount of work [i] done by an electric current [i] in a unit time [i] ... 

 . Research reactors are used for radioisotope Radionuclide

Atoms of chemical elements may have many isotopes with the same atomic numbers but different atomic weights /... 

 production and for beamline experiments with free neutron Neutron

In physics [i], the neutron is a subatomic particle [i] with no net electric charge [i] and a mass [i] o ... 

s. Historically, the first use of nuclear reactors was the production of weapons grade plutonium for nuclear weapon Nuclear weapon

A nuclear weapon derives its destructive force from nuclear reaction [i]s of fission [i] ... 

s. Another military use is submarine / ship propulsion . Currently all commercial nuclear reactors are based on nuclear fission Nuclear fission

For the generation of electrical power by fission, see Nuclear power plant [i] ... 

, and are considered problematic by some for their safety and health risks.

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Encyclopedia



A nuclear reactor is a device in which nuclear chain reaction Nuclear chain reaction

A nuclear chain reaction occurs when on average more than one nuclear reaction [i] is caused by another ... 

s are initiated, controlled, and sustained at a steady rate .

Nuclear reactors are used for many purposes. The most significant current use is for the generation of electrical power Electric power

Electric power is defined as the amount of work [i] done by an electric current [i] in a unit time [i] ... 

 . Research reactors are used for radioisotope Radionuclide

Atoms of chemical elements may have many isotopes with the same atomic numbers but different atomic weights /... 

 production and for beamline experiments with free neutron Neutron

In physics [i], the neutron is a subatomic particle [i] with no net electric charge [i] and a mass [i] o ... 

s. Historically, the first use of nuclear reactors was the production of weapons grade plutonium for nuclear weapon Nuclear weapon

A nuclear weapon derives its destructive force from nuclear reaction [i]s of fission [i] ... 

s. Another military use is submarine / ship propulsion .

Currently all commercial nuclear reactors are based on nuclear fission Nuclear fission

For the generation of electrical power by fission, see Nuclear power plant [i]
... 

, and are considered problematic by some for their safety and health risks. Conversely, some consider nuclear power to be a safe and pollution-free method of generating electricity. Fusion power Fusion power

Fusion power refers to power generated by nuclear fusion [i] reactions. ... 

 is an experimental technology based on nuclear fusion Nuclear fusion

In physics [i], nuclear fusion is the process by which multiple nuclei [i] join together ... 

 instead of fission. There are other devices in which nuclear reactions occur in a controlled fashion, including radioisotope thermoelectric generator Radioisotope thermoelectric generator

A radioisotope thermoelectric generator is a simple electrical generator [i] which obtains its power fro ... 

s and atomic batteries, which generate heat and power by exploiting passive radioactive decay, as well as Farnsworth-Hirsch fusor Fusor

The FarnsworthHirsch Fusor, or simply fusor, is an apparatus designed by Philo T. Farnsworth [i] t ... 

s, in which controlled nuclear fusion is used to produce neutron radiation.

Applications

  • Nuclear power Nuclear power

    Nuclear power is the controlled use of nuclear reactions [i] to release energy for work including propulsion [i] ... 

    :
    • Heat for electricity generation
    • Heat for domestic and industrial heating
    • Hydrogen Hydrogen

      |-

| Triple point [i] || 13.8033 K, 7.042 kPa
... 

 production
    • Desalination Desalination

      Desalination refers to any of several processes that remove the excess salt [i] and othe... 

  • Nuclear propulsion:
    • Nuclear marine propulsion
    • Proposed nuclear thermal rocket Nuclear thermal rocket

      In a nuclear thermal rocket a working fluid, usually hydrogen [i], is heated in a high temperature nuclear reactor [i] ... 

      s
    • Proposed nuclear pulse propulsion Nuclear pulse propulsion

      Nuclear pulse propulsion is a proposed method of spacecraft propulsion [i] that uses nuclear explosion [i] ... 

       rockets
  • Transmutation of elements:
    • Production of plutonium Plutonium

      Plutonium is a radioactive [i], metal [i]lic chemical element [i].... 

      , often for use in nuclear weapon Nuclear weapon

      A nuclear weapon derives its destructive force from nuclear reaction [i]s of fission [i] ... 

      s
    • Creating various radioactive isotopes, such as americium Americium

      Americium is a synthetic element [i] in the periodic table [i] that has the symbol Am and atomic number [i] ... 

       for use in smoke detector Smoke detector

      A smoke detector or smoke alarm is an active fire protection [i] device, subject to stringent bounding [i] ... 

      s, and cobalt-60, molybdenum-99 and others, used for imaging and medical treatment
  • Research applications including:
    • Providing a source of neutron and positron radiation
    • Development of nuclear technology Nuclear technology

      Nuclear technology is technology that involves the reactions [i] of atomic nuclei [i]... 



History


Although mankind has only tamed nuclear power recently, the first nuclear reactors were naturally occurring. Fifteen natural fission reactors have so far been found in three separate ore deposits at the Oklo mine in Gabon Gabon


Gabon, officially the Gabonese Republic, is a country in west central Africa [i]. ... 

, West Africa West Africa

West Africa or Western Africa is the west [i]ernmost region [i] of the Africa [i]n continent [i]. ... 

. First discovered in 1972 by French physicist Francis Perrin, they are collectively known as the Oklo Fossil Reactors Natural nuclear fission reactor

A natural nuclear fission reactor is a uranium [i] deposit where analysis of isotope ratios has shown th ... 

. These reactors ran for approximately 150 million years, averaging 100 kW of power output during that time. Also, stars rely on nuclear fusion for their output of heat, light and other radiations. The concept of a natural nuclear reactor was theorized as early as 1956 by Paul Kuroda at the University of Arkansas University of Arkansas

[i] [[land-grant]... 

 

Enrico Fermi Enrico Fermi

Enrico Fermi was an Italian [i] physicist [i] most noted for his work on beta decay [i], the deve ... 

 and Leó Szilárd Leó Szilárd

Le Szilrd was a Hungarian [i]-American [i] physicist [i] who conceived the nuclear chain reaction [i] ... 

, while both were at the University of Chicago University of Chicago

The University of Chicago is a private university [i] located principally in the Hyde Park [i]... 

, were the first to build a nuclear pile and demonstrate a controlled chain reaction on December 2, 1942. In 1955 they shared for the nuclear reactor.

The first nuclear reactors were used to generate plutonium for nuclear weapons. Additional reactors were used in the navy to propel submarine Submarine

A submarine is a specialized watercraft [i] that can operate underwater [i].... 

s and aircraft carrier Aircraft carrier

Additive synthesis is a technique of audio synthesis which creates music [i]al timbre [i].
... 

s. In the mid-1950s 1950s

The 1950s was the decade spanning the years 1950 to 1959.... 

, both the Soviet Union Soviet Union

The Union of Soviet Socialist Republics , more commonly known as the Soviet Union, was a Communist state [i] ... 

 and western countries were expanding their nuclear research to include non-military uses of the atom. However, as with the military program, much of the non-military work was done in secret.

On December 20, 1951, electric power from a nuclear powered generator was produced for the first time at Experimental Breeder Reactor-I Experimental Breeder Reactor I

Experimental Breeder Reactor I is a decomissioned research reactor [i] and U.S. [i] National Historic Landmark [i]... 

  located near Arco, Idaho Arco, Idaho

Arco is a city in Butte County [i], Idaho [i], United States [i]. ... 

. On June 26, 1954, at 5:30 pm, the world's first nuclear power plant to generate electricity began operations at Obninsk, Kaluga Oblast Kaluga Oblast

Kaluga Oblast is a federal subject [i] of Russia [i]. ... 

, USSR Soviet Union

The Union of Soviet Socialist Republics , more commonly known as the Soviet Union, was a Communist state [i] ... 

. It produced 5 megawatts, enough to power 2,000 homes. .



The world's first commercial scale nuclear power station, Calder Hall Sellafield

Sellafield is the name of a nuclear site, close to the village and railway station of
... 

, began generation on October 17, 1956 Another early power reactor was the Shippingport Reactor Shippingport Reactor

The Shippingport reactor, located near the present-day Beaver Valley Nuclear Generating Station [i] on t ... 

 in Pennsylvania Pennsylvania

The Commonwealth of Pennsylvania is a state [i] in the northeastern [i] ... 

 .

Even before the 1979 Three Mile Island Three Mile Island accident

On March 28 [i], 1979 [i], the Unit 2 nuclear power plant [i] on Three Mile Island suffered a partial co ... 

 accident, new orders for nuclear plants in the U.S. had ceased for economic reasons primarily related to greatly extended construction times. As of 2004 2004

2004 was a leap year starting on Thursday [i] of the Gregorian calendar [i].
... 

, no new nuclear plants have been ordered in the USA since 1978 , although that may change by 2010 .

Unlike the Three Mile Island accident, the 1986 Chernobyl accident Chernobyl disaster

The Chernobyl disaster occurred at 01:23 a.m.... 

 did not increase regulations affecting Western reactors. This was because the Chernobyl reactors were known to be an unsafe design, using the RBMK, without containment buildings and operated unsafely, and the West had little to learn from them . There was however political fallout: Italy Italy

Italy, officially the Italian Republic , is a Southern European [i] country. ... 

 held a referendum the next year in 1987, the results of which led to a shutdown of the country's four nuclear power plants.

In 1992 the Turkey Point Nuclear Generating Station was hit directly by Hurricane Andrew Hurricane Andrew

Hurricane Andrew was the second most destructive hurricane [i] in U.S. history [i], and the final of thr ... 

. Over $90 million of damage was done, largely to a water tank and to a smokestack of one of the fossil-fueled units on-site, but the containment buildings were undamaged .

The first organization to develop utilitarian nuclear power, the U.S. Navy United States Navy

The United States Navy is the branch of the United States armed forces [i] responsible for conducting naval [i] ... 

, is the only organization worldwide with a totally clean record. This is perhaps because of the stringent demands of Admiral Hyman G. Rickover Hyman G. Rickover

Admiral [i] Hyman George Rickover, U.S. Navy [i], was known as the "Father of the Nuclear Navy [i] ... 

, who was the driving force behind nuclear marine propulsion. The U.S. Navy has operated more nuclear reactors than any other entity, other than the Soviet Navy Soviet Navy

The Soviet Navy was the naval [i] arm of the Soviet [i] armed forces [i]. ... 

, with no publicly known major incidents. Two U.S. nuclear submarines, USS Scorpion and Thresher, have been lost at sea, though for reasons not related to their reactors, and their wrecks are situated such that the risk of nuclear pollution is considered low.

The future of the industry

As of 2006 2006

2006 is a common year starting on Sunday [i] of the Gregorian calendar [i].
... 

, Watts Bar 1, which came on-line in 1997, was the last U.S. commercial nuclear reactor to go on-line. This is often quoted as evidence of a successful worldwide campaign for nuclear power phase-out Nuclear power phase-out

A nuclear power phase-out is the discontinuation of usage of nuclear power [i] for energy production.... 

. However, political resistance to nuclear power has only ever been successful in parts of Europe, in New Zealand, in the Philippines, and in the United States. Even in the US and throughout Europe, investment in research and in the nuclear fuel cycle Nuclear fuel cycle

The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel [i] thr ... 

 has continued, and some experts predict that electricity shortages, fossil fuel price increases and concern over greenhouse gas Greenhouse gas

Greenhouse gases are gas [i]eous components of the atmosphere [i] that contribute to ... 

 emissions will renew the demand for nuclear power plants.

Many countries remain active in developing nuclear power, including Japan, China and India, all actively developing both fast and thermal technology, South Korea and the United States, developing thermal technology only, and South Africa and China, developing versions of the Pebble Bed Modular Reactor . Finland and France actively pursue nuclear programs; Finland has a new European Pressurized Reactor European Pressurized Reactor

The European Pressurized Reactor is a third generation [i] fission pressurized water reactor [i] ... 

 under construction by Areva Areva

AREVA is a France [i]-based multinational industrial conglomerate that deals in energy, especially in nuclear power [i] ... 

. Japan has an active nuclear construction program with new units brought on-line in 2005. In the U.S., three consortia responded in 2004 to the U.S. Department of Energy United States Department of Energy

The United States Department of Energy is a Cabinet [i]-level department of the United States [i] ... 

's solicitation under the Nuclear Power 2010 Program and were awarded matching funds - the Energy Policy Act of 2005 authorized subsidies for up to six new reactors, and authorized the Department of Energy United States Department of Energy

The United States Department of Energy is a Cabinet [i]-level department of the United States [i] ... 

 to build a reactor based on the Generation IV Very-High-Temperature Reactor Very high temperature reactor

The Very High Temperature Reactor is a Generation IV reactor [i] concept that uses a graphite [i]-modera ... 

 concept to produce both electricity and hydrogen Hydrogen

|-
| Triple point [i] || 13.8033 K, 7.042 kPa
... 

. As of the early 21st century, nuclear power is of particular interest to both China and India to serve their rapidly growing economies - both are developing fast breeder reactor Fast breeder reactor

The fast breeder or fast breeder reactor is a fast neutron reactor [i] designed to breed fuel ... 

s. See also future energy development Future energy development

Future energy development faces great challenges due to an increasing world population, demands for high... 

. In the energy policy of the United Kingdom Energy policy of the United Kingdom

The Energy policy of the United Kingdom is a set of official publications and activities directed at the... 

 it is recognized that there is a likely future energy supply shortfall, which may have to be filled by either new nuclear plant construction or maintaining existing plants beyond their programmed lifetime.

On September 22, 2005 it was announced that two sites in the U.S. had been selected to receive new power reactors - see Nuclear Power 2010 Program.

It is possible that the first new nuclear power plant to be built in the United States since the 1970s may be installed in the remote town of Galena, Alaska. The town's City Council approved the idea, and Toshiba Toshiba

is a multinational [i] high technology [i] electrical and electronics [i] manufact ... 

 proposed to install its model 4S "nuclear battery" in Galena free of charge as a test.

See also nuclear power phase-out Nuclear power phase-out

A nuclear power phase-out is the discontinuation of usage of nuclear power [i] for energy production.... 

, nuclear energy policy.

Types of reactors


A number of reactor technologies have been developed. Fission reactors can be divided roughly into two classes, depending on the energy of the neutrons that are used to sustain the fission chain reaction.

  • Thermal reactors use slow or thermal neutron Neutron temperature

    The neutron temperature, also called the neutron energy, indicates a free neutron's [i] ... 

    s. These are characterized by having moderating materials which are intended to slow the neutrons until they approach the average kinetic energy of the surrounding particles, that is, until they are thermalized. Thermal neutrons have a far higher probability of fissioning U-235, and a lower probability of capture by U-238 than the faster neutrons that result from fission do. As well as the moderator, thermal reactors have fuel , containments, pressure vessels, shielding, and instrumentation to monitor and control the reactor's systems. Most power reactors are of this type, and the first plutonium production reactors were thermal reactors using graphite Graphite

    Graphite is one of the allotropes of [i] carbon [i]. ... 

     as the moderator. Some thermal power reactors are more thermalised than others; Graphite and heavy water moderated plants  tend to be more thoroughly thermalised than PWR Pressurized water reactor

    Pressurised water reactors are nuclear power reactor [i]s that use water [i] under high ... 

    s and BWR Boiling water reactor

    A boiling water reactor is a light water reactor [i] is a type of nuclear reactor developed by the Gener ... 

    s, which use light water as the moderator .
  • Fast reactors Fast neutron reactor

    A fast neutron reactor or simply a fast reactor is a category of nuclear reactor [i] in which the ... 

    use fast neutrons to sustain the fission chain reaction, and are characterized by the lack of moderating material. They require highly enriched fuel , or plutonium Plutonium

    Plutonium is a radioactive [i], metal [i]lic chemical element [i].... 

     in order to reduce the amount of U-238 that would otherwise capture fast neutrons. Some are capable of producing more fuel than they consume, usually by converting U-238 to Pu-239. Some early power stations were fast reactors, as are some Russian naval propulsion units, and construction of prototypes is continuing, see fast breeder Fast breeder reactor

    The fast breeder or fast breeder reactor is a fast neutron reactor [i] designed to breed fuel ... 

    , but overall the class has not achieved the success of thermal reactors in any application. An example of this type of reactor is the Fast Breeder Reactor .


Thermal power reactors can again be divided into three types, depending on whether they use pressurised fuel channels, a large pressure vessel Pressure vessel

A pressure vessel is a closed, rigid, container designed to hold gases or liquids at a pressure [i] diff ... 

, or gas cooling.

  • Pressure vessels holding steam heated by the reactor are used by most commercial and naval reactors. This serves as a layer of shielding and containment.


  • Pressurised channels are used by the RBMK and CANDU CANDU reactor

    The CANDU reactor is a Pressurized Heavy Water Reactor [i] developed ini ... 

     reactors. Channel-type reactors can be refuelled under load, which has advantages discussed under CANDU reactor CANDU reactor

    The CANDU reactor is a Pressurized Heavy Water Reactor [i] developed ini ... 

    .


  • Gas-cooled reactors are cooled by a circulating inert gas, usually helium Helium

    |-

| 3He || 0.000137%* || colspan="4" | He is stable [i] with 1 neutron [i]
... 

, but nitrogen Nitrogen

Nitrogen is a chemical element [i] which has the symbol N and atomic number [i] 7 in the periodic table [i] ... 

 and carbon dioxide Carbon dioxide

Carbon dioxide is a chemical compound [i] composed of one carbon [i] and two oxygen [i] atoms. ... 

 have also been used. Utilisation of the heat varies, depending on the reactor. Some reactors run hot enough that the gas can directly power a gas turbine. Older designs usually run the gas through a heat exchanger to make steam for a steam turbine. The pebble bed reactor uses a gas-cooled design.

Since water serves as a moderator, it cannot be used as a coolant in a fast reactor. Most designs for fast power reactors have been cooled by liquid metal, usually molten sodium Sodium

Sodium is a chemical element [i] which has the symbol Na , atomic number 11, atomic mass 22.9898 g/mol, oxidation number [i] ... 

. They have also been of two types, called pool and loop reactors.

Further detail on the classification of Nuclear reactors can be found at Classification of Nuclear Reactors.

Current families of reactors

  • Pool type reactor
  • Pressurized water reactor Pressurized water reactor

    Pressurised water reactors are nuclear power reactor [i]s that use water [i] under high ... 

  • Boiling water reactor Boiling water reactor

    A boiling water reactor is a light water reactor [i] is a type of nuclear reactor developed by the Gener ... 

  • Fast breeder reactor Fast breeder reactor

    The fast breeder or fast breeder reactor is a fast neutron reactor [i] designed to breed fuel ... 

  • Pressurized Heavy Water Reactor  or CANDU CANDU reactor

    The CANDU reactor is a Pressurized Heavy Water Reactor [i] developed ini ... 

  • United States Naval reactor

Obsolete types still in service

  • Magnox reactor Magnox

    Magnox is a now obsolete type of nuclear power reactor [i] which was designed and used i ... 

  • Advanced gas-cooled Reactor Advanced gas-cooled reactor

    An Advanced Gas Cooled Reactor is a type of nuclear reactor [i]. ... 

  • Light water cooled graphite moderated reactor

Other types of reactors

  • Aqueous Homogeneous Reactor
  • Liquid Fluoride Reactor

Advanced reactors

More than a dozen advanced reactor designs are in various stages of development.Some are evolutionary from the PWR Pressurized water reactor

Pressurised water reactors are nuclear power reactor [i]s that use water [i] under high ... 

, BWR Boiling water reactor

A boiling water reactor is a light water reactor [i] is a type of nuclear reactor developed by the Gener ... 

 and PHWR designs above, some are more radical departures. The former include the Advanced Boiling Water Reactor , two of which are now operating with others are under construction, and the planned passively safe ESBWR and AP1000 units . The best-known radical new design is the Pebble Bed Modular Reactor , a High Temperature Gas Cooled Reactor . The Clean And Environmentally Safe Advanced Reactor  is a nuclear reactor concept that uses steam as a moderator - this design is still in development. Possible designs of subcritical reactors exist on the drawing board, notably the energy amplifier, awaiting political support and funding. Some, such as the Integral Fast Reactor , have been cancelled due to a political climate unfavorable to nuclear power.

Generation IV reactors

Even more-advanced reactors are also on the drawing boards. These are the Generation IV reactor Generation IV reactor

Generation IV reactors are a set of theoretical nuclear reactor designs currently being researched.... 

s, which are divided into six overall design classes.

  • Gas cooled fast reactor Gas-cooled fast reactor

    The Gas-Cooled Fast Reactor system is a Generation IV reactor [i] concept that features a fast-neutron spectrum [i] ... 

  • Lead cooled fast reactor Lead cooled fast reactor

    The Lead-cooled Fast Reactor is a Generation IV reactor [i] that features a fast neutron [i] spectrum,... 

  • Molten salt reactor Molten salt reactor

    A molten salt reactor is a type of nuclear reactor [i] where the primary coolant is a molten salt.

... 


  • Sodium-cooled fast reactor Sodium-cooled fast reactor

    The SFR is a project that builds on two closely related existing projects, the LMFBR [i] and the Integral Fast Reactor [i] ... 

  • Supercritical water reactor Supercritical water reactor

    The Supercritical water reactor is a Generation IV reactor [i] concept that uses supercritical water [i] ... 

  • Very high temperature reactor Very high temperature reactor

    The Very High Temperature Reactor is a Generation IV reactor [i] concept that uses a graphite [i]-modera ... 

  • Fission fragment reactor

Nuclear fuel cycle

Main article: nuclear fuel cycle Nuclear fuel cycle

The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel [i] thr ... 



Thermal reactors generally depend on refined and enriched uranium Enriched uranium

Enriched uranium is uranium [i] whose uranium-235 [i] content has been increased through the process of ... 

. Some nuclear reactors can operate with a mixture of plutonium and uranium . The process by which uranium ore is mined, processed, enriched, used, possibly reprocessed and disposed of is known as the nuclear fuel cycle Nuclear fuel cycle

The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel [i] thr ... 

.

Uranium is sampled and mined Mining

Mining is the extraction of valuable [i] mineral [i]s or other geological [i] materials f ... 

 as other metals are, via open-pit mining or leach mining. Raw uranium ore found in the United States ranges from 0.05% to 0.3% uranium oxide. Uranium ore is not rare; the largest probable resources, extractable at a cost of US$80 per kilogram or cheaper, are located in Australia Australia

Australia, officially the Commonwealth of Australia, is a country in the Southern Hemisphere [i] c ... 

, Kazakhstan Kazakhstan

Kazakhstan, also spelled Kazakstan, , officially the Republic of Kazakhstan, is a country th... 

, Canada Canada

Canada is the world's second-largest [i] country by total area, occupying most ... 

, South Africa South Africa

The Republic of South Africa is a country located at the southern tip of the Africa [i]n continent [i]. ... 

, Brazil Brazil

Brazil, officially the Federative Republic of Brazil , is the largest and most populous country [i] ... 

, Namibia Namibia

Namibia, officially the Republic of Namibia, is a country in southern Africa [i] on the Atlantic [i] ... 

, Russia Russia

Russia , also the Russian Federation , is a country [i] that stretches over a vast expanse of Eurasia [i] ... 

, and the United States United States

The United States of America, also known as the United States, the U.S., the U.S.A., a... 

.

The raw ore is then milled, where it is ground and chemically leached. The resulting powder of natural uranium oxide is called "yellowcake Yellowcake

Yellowcakes are uranium [i] concentrates obtained from leach solutions [i]. ... 

". The yellowcake powder is then converted to uranium hexafluoride Uranium hexafluoride

Uranium hexafluoride, or UF6, is a compound used in the uranium [i] enrichment [i] ... 

 to prepare for enrichment.

Under 1% of the uranium found in nature is the easily fissionable U-235 isotope and as a result most reactor designs require enriched fuel.
Enrichment involves increasing the percentage of U-235 and is usually done by means of gaseous diffusion or gas centrifuge Gas centrifuge

The gas centrifuge is a hyper-centrifuge [i] used to produce enriched uranium [i]. ... 

. The enriched result is then converted into uranium dioxide Uranium dioxide

Uranium dioxide, an oxide [i] of uranium [i], also known as urania or uranic oxide is a blac ... 

 powder, which is pressed and fired onto pellet form. These pellets are stacked into tubes which are then sealed and called fuel rod Nuclear fuel

Nuclear fuel is any material that can be consumed to derive nuclear energy [i], by analogy to chemical fuel [i] ... 

s. Many of these fuel rods are used in each nuclear reactor.

Most BWR and PWR commercial reactors use uranium enriched to about 4% U-235, many research reactors use highly enriched, or weapons grade uranium, while some commercial reactors with a high neutron economy do not require the fuel to be enriched at all.

Fueling of nuclear reactors

The amount of energy in the reservoir of nuclear fuel Nuclear fuel

Nuclear fuel is any material that can be consumed to derive nuclear energy [i], by analogy to chemical fuel [i] ... 

 is frequently expressed in terms of "full-power days," which is the number of 24-hour periods a reactor is scheduled for operation at full power output for the generation of heat energy. The number of full-power days in a reactor's operating cycle is related to the amount of fissile uranium-235 Uranium-235

Uranium-235 is an isotope [i] of uranium [i] that differs from the element's other common isotope, uranium-238 [i]... 

  contained in the fuel assemblies at the beginning of the cycle. A higher percentage of U-235 in the core at the beginning of a cycle will permit the reactor to be run for a greater number of full-power days.

At the end of the operating cycle, the fuel in some of the assemblies is "spent," and is discharged and replaced with new fuel assemblies. Although in practice, it is the buildup of reaction poisons in nuclear fuel that determines the lifetime of nuclear fuel in a reactor; long before all possible fissions have taken place, the buildup of long-lived neutron absorbing fission products damps out the chain reaction. The fraction of the reactor's fuel core replaced during refueling is typically one-fourth for a boiling-water reactor and one-third for a pressurized-water reactor.

Not all reactors need to be shut down for refueling; for example, pebble bed reactors, RBMK reactors,molten salt reactor Molten salt reactor

A molten salt reactor is a type of nuclear reactor [i] where the primary coolant is a molten salt.
... 

s, Magnox Magnox

Magnox is a now obsolete type of nuclear power reactor [i] which was designed and used i ... 

 and CANDU CANDU reactor

The CANDU reactor is a Pressurized Heavy Water Reactor [i] developed ini ... 

 reactors allow fuel to be shifted through the reactor while it is running. In a CANDU reactor, this also allows individual fuel elements to be moved about within the reactor core to places that are best suited to the amount of U-235 in the fuel element.

The amount of energy extracted from nuclear fuel is called its "burn up," which is expressed in terms of the heat energy produced per initial unit of fuel weight. Burn up is commonly expressed as megawatt days thermal per metric ton of initial heavy metal.

Waste management

The final stage of the nuclear fuel cycle is the management of the still highly radioactive, "spent" fuel, which constitutes the most problematic component of the nuclear waste Radioactive waste

Radioactive waste is waste type [i] containing radioactive [i] chemical element [i]s ... 

 stream. After fifty years of nuclear power the question of how to deal with this material remains fraught with safety concerns and technical problems, and one of the most important lines of criticism of the industry is based on the long-term risks and costs associated with dealing with the waste.

Management of the spent fuel can include various combinations of storage, reprocessing, and disposal. In practice storage has been the primary modality so far. Typically the spent fuel rods are stored in a pool of water which is usually located on-site. The water provides both cooling for the still-decaying uranium, and shielding from the continuing radioactivity. After a few decades some on-site storage involves moving the now cooler, less radioactive fuel to a dry-storage facility, where the fuel is stored in steel and concrete containers which are monitored carefully.

Another, more permanent method of disposal of high-level nuclear waste calls for the material to be buried deep underground in certain geological formations. The Canadian government, for example, is seriously considering this method of disposal, known as the Deep Geological Disposal concept. Under the current plan, a vault is to be dug 500 to 1000 meters below ground, under the Canadian Shield, one of the most stable landforms on the planet. The vaults are to be dug inside geological formations known as batholith Batholith

A batholith is a large emplacement of igneous [i] intrusive [i] rock that forms from cooled ... 

s
, formed about a billion years ago. The used fuel bundles will be encased in a corrosion-resistant container, and further surrounded by a layer of buffer material, possibly of a special kind of clay . The case itself is designed to last for thousands of years, while the clay would further slow the corrosion rates of the container. The batholiths themselves are chosen for their low ground-water movement rates, geological stability, and low economic value.

The Finnish government has already started building a vault to store nuclear waste 500 to 1000 meters below ground, not far from the nuclear plant at Olkiluoto Olkiluoto

Olkiluoto is an island located in western Finland [i] in the municipality of Eurajoki [i].
... 

.

Storing high level nuclear waste above ground for a century or so is considered appropriate by many scientists. This allows for the material to be more easily observed and any problems detected and managed, while the decay over this time period significantly reduces the level of radioactivity and the associated harmful effects to the container material. It is also considered likely that over the next century newer materials will be developed which will not break down as quickly when exposed to a high neutron flux thus increasing the longevity of the container once it is permanently buried.

Reprocessing is attractive in principle because it can recycle nuclear fuel and it can prepare the waste material for disposal. Considerable experience with reprocessing in France France

France, officially the French Republic, is a country [i] whose metropolitan territory [i] ... 

 however, has indicated that a one way fuel cycle based on extracting and processing fresh supplies of uranium and storing the spent fuel is more economical than reprocessing, not the least because in the process of plutonium extraction, the volume of high-level liquid radioactive waste increases about 17-fold.

Natural nuclear reactors

A natural nuclear fission reactor Natural nuclear fission reactor

A natural nuclear fission reactor is a uranium [i] deposit where analysis of isotope ratios has shown th ... 

 can occur under certain circumstances that mimic the conditions in a constructed reactor. The only known natural nuclear reactor formed 2 billion years ago in Oklo, Gabon, Africa.
Such reactors can no longer form on Earth: radioactive decay over this immense time span has reduced the proportion of U-235 in naturally occurring uranium to below the amount required to sustain a chain reaction.

The natural nuclear reactors formed when a uranium-rich mineral deposit became inundated with groundwater that acted as a neutron moderator, and a strong chain reaction took place. The water moderator would boil away as the reaction increased, slowing it back down again and preventing a meltdown. The fission reaction was sustained for hundreds of thousands of years.

These natural reactors are extensively studied by scientists interested in geologic radioactive waste disposal. They offer a case study of how radioactive isotopes migrate through the earth's crust. This is a significant area of controversy as opponents of geologic waste disposal fear that isotopes from stored waste could end up in water supplies or be carried into the environment.

See also

  • Electricity generation
  • Energy amplifier
  • Enrico Fermi Enrico Fermi

    Enrico Fermi was an Italian [i] physicist [i] most noted for his work on beta decay [i], the deve ... 

  • Future energy development Future energy development

    Future energy development faces great challenges due to an increasing world population, demands for high... 

  • Green Field status
  • List of nuclear accidents Nuclear and radiation accidents

    This article covers notable accidents involving nuclear devices and radioactive [i] material ... 

  • List of nuclear reactors List of nuclear reactors

    List of nuclear reactors is a comprehensive annotated list of all the nuclear reactor [i]s of the world, ... 

  • List of United States Naval reactors
  • Manhattan Project Manhattan Project

    The Manhattan Project refers to the effort to develop the first nuclear weapon [i]s during World War II [i] ... 

  • Nuclear fission Nuclear fission

    For the generation of electrical power by fission, see Nuclear power plant [i]

... 


  • Nuclear fusion Nuclear fusion

    In physics [i], nuclear fusion is the process by which multiple nuclei [i] join together ... 

  • Nuclear marine propulsion
  • Nuclear meltdown
  • Nuclear physics
  • Nuclear power plant Nuclear power plant

    A nuclear power plant is a thermal [i] power station [i] in which the heat source is one or more nuclear reactor [i] ... 

  • Nuclear power Nuclear power

    Nuclear power is the controlled use of nuclear reactions [i] to release energy for work including propulsion [i] ... 

  • Nuclear Reactor Operator Badge Nuclear Reactor Operator Badge

    The Nuclear Reactor Operator Badge is a decoration of the United States Army [i] which was issued betwee ... 

  • Nuclear reactor physics
  • Nuclear waste Radioactive waste

    Radioactive waste is waste type [i] containing radioactive [i] chemical element [i]s ... 

  • Pebble bed reactor
  • Power plant Power station

    A power station or power plant is a facility for the generation [i] of electric power [i] ... 

  • SCRAM
  • SSTAR SSTAR

    SSTAR is an acronym for the "small, sealed, transportable, autonomous reactor [i]" - bei ... 

     - LLNL Lawrence Livermore National Laboratory

    The Lawrence Livermore National Laboratory is a United States Department of Energy [i] national laboratory [i] ... 

     design for a "world" reactor
  • Technology assessment
  • United States Naval reactor

References


External links

  • publishing uranium price since 1968.
  • provides lots of statistics and information on the industry.
  • supervises the US Nuclear industry
  • The Idaho National Engineering and Environmental Laboratory developed nuclear reactor technology in the United States -
  • The International Atomic Energy Agency International Atomic Energy Agency

    The International Atomic Energy Agency/IAEA, was established as an autonomous organization on July 29 [i] ... 

      works with its Member States and multiple partners worldwide to promote safe, secure and peaceful nuclear technologies.
    • on Gas Cooled Reactors
  • [https://www.pbmr.co.za/ The Pebble Bed Modular Reactor] -
  • - A pro nuclear site
  • - An anti-nuclear site
  • by Bernard Cohen. Pro nuclear book which compares risks of nuclear power with other methods of energy generation.
  • - a very information-rich resource about Canadian CANDU reactors.
  • Online book by Albert J. Fritsch, Arthur H. Purcell, and Mary Byrd Davis
  • - Eagle and Eagle TV production about David Hahn's nuclear reactor experiment
  • What happened when teenager David Hahn tried a dangerous experiment in his back yard