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104-452: The construction of the FFTF was completed in 1978, and the first reaction took place in 1980. From April 1982 to April 1992 it operated as a national research facility to test various aspects of commercial reactor design and operation, especially relating to breeder reactors . The FFTF is not a breeder reactor itself, but rather a sodium-cooled fast neutron reactor , as the name suggests. It

208-433: A chain reaction , as well as the ratio of breeding to fission. On the other hand, a fast reactor needs no moderator to slow down the neutrons at all, taking advantage of the fast neutrons producing a greater number of neutrons per fission than slow neutrons. For this reason ordinary liquid water , being a moderator and neutron absorber , is an undesirable primary coolant for fast reactors. Because large amounts of water in

312-769: A fast neutron reactor . The leaders in national experience with PWRs, offering reactors for export, are the United States (which offers the passively safe AP1000 , a Westinghouse design, as well as several smaller, modular, passively safe PWRs, such as the Babcock & Wilcox MPower , and the NuScale MASLWR), the Russian Federation (offering both the VVER-1000 and the VVER-1200 for export),

416-435: A heavy water reactor , which uses heavy water as a neutron moderator. While ordinary water has some heavy water molecules in it, it is not enough to be important in most applications. In pressurized water reactors the coolant water is used as a moderator by letting the neutrons undergo multiple collisions with light hydrogen atoms in the water, losing speed in the process. This moderating of neutrons will happen more often when

520-702: A "National Nuclear Historic Landmark". Achievements cited include: The probable successor to the FFTF will be the Versatile Test Reactor , which will roughly have the same size and capabilities as future test reactor and which will be built at Idaho National Laboratory in Idaho or Oak Ridge National Laboratory in Tennessee in the 2020s. 46°26′07″N 119°21′36″W  /  46.435284°N 119.360061°W  / 46.435284; -119.360061 Breeder reactor A breeder reactor

624-460: A blend of uranium, plutonium, and zirconium (used because it is "transparent" to neutrons). Enriched uranium can be used on its own. Many designs surround the reactor core in a blanket of tubes that contain non-fissile uranium-238, which, by capturing fast neutrons from the reaction in the core, converts to fissile plutonium-239 (as is some of the uranium in the core), which is then reprocessed and used as nuclear fuel. Other FBR designs rely on

728-455: A breeder reactor then needs to be reprocessed to remove those neutron poisons . This step is required to fully utilize the ability to breed as much or more fuel than is consumed. All reprocessing can present a proliferation concern, since it can extract weapons-usable material from spent fuel. The most common reprocessing technique, PUREX , presents a particular concern since it was expressly designed to separate plutonium. Early proposals for

832-535: A chain reaction), fission products are viewed as nuclear 'ashes' left over from consuming fissile materials. Furthermore, only seven long-lived fission product isotopes have half-lives longer than a hundred years, which makes their geological storage or disposal less problematic than for transuranic materials. With increased concerns about nuclear waste, breeding fuel cycles came under renewed interest as they can reduce actinide wastes, particularly plutonium and minor actinides. Breeder reactors are designed to fission

936-438: A commercial pressurized water reactor assembly — and inserted into guide tubes within a fuel element. A control rod is removed from or inserted into the central core of a nuclear reactor in order to control the number of neutrons which will split further uranium atoms. This in turn affects the thermal power of the reactor, the amount of steam generated, and hence the electricity produced. The control rods are partially removed from

1040-490: A compromise of the reactor core's integrity, the resulting release of the light-water moderator will act to stop the nuclear reaction and shut the reactor down. This capability is known as a negative void coefficient of reactivity . Data from the International Atomic Energy Agency in 2009: The light-water reactor produces heat by controlled nuclear fission . The nuclear reactor core is

1144-538: A fission reactor. Breeder reactors by design have high burnup compared to a conventional reactor, as breeder reactors produce more of their waste in the form of fission products, while most or all of the actinides are meant to be fissioned and destroyed. In the past, breeder-reactor development focused on reactors with low breeding ratios, from 1.01 for the Shippingport Reactor running on thorium fuel and cooled by conventional light water to over 1.2 for

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1248-524: A grinding process to achieve a uniform pellet size. The uranium oxide is dried before inserting into the tubes to try to eliminate moisture in the ceramic fuel that can lead to corrosion and hydrogen embrittlement. The pellets are stacked, according to each nuclear core's design specifications, into tubes of corrosion-resistant metal alloy. The tubes are sealed to contain the fuel pellets: these tubes are called fuel rods. The finished fuel rods are grouped in special fuel assemblies that are then used to build up

1352-416: A half-life between 91 and 200,000 years. As a result of this physical oddity, after several hundred years in storage, the activity of the radioactive waste from an FBR would quickly drop to the low level of the long-lived fission products . However, to obtain this benefit requires the highly efficient separation of transuranics from spent fuel. If the fuel reprocessing methods used leave a large fraction of

1456-1190: A heavily moderated thermal design, evolved into the fast reactor concept, using light water in a low-density supercritical form to increase the neutron economy enough to allow breeding. Aside from water-cooled, there are many other types of breeder reactor currently envisioned as possible. These include molten-salt cooled , gas cooled , and liquid-metal cooled designs in many variations. Almost any of these basic design types may be fueled by uranium , plutonium , many minor actinides , or thorium , and they may be designed for many different goals, such as creating more fissile fuel, long-term steady-state operation, or active burning of nuclear wastes . Extant reactor designs are sometimes divided into two broad categories based upon their neutron spectrum, which generally separates those designed to use primarily uranium and transuranics from those designed to use thorium and avoid transuranics. These designs are: All current large-scale FBR power stations were liquid metal fast breeder reactors (LMFBR) cooled by liquid sodium . These have been of one of two designs: There are only two commercially operating breeder reactors as of 2017 :

1560-457: A light-water reactor for longer than 100,000 years, the transuranics would be the main source of radioactivity. Eliminating them would eliminate much of the long-term radioactivity from the spent fuel. In principle, breeder fuel cycles can recycle and consume all actinides, leaving only fission products. As the graphic in this section indicates, fission products have a peculiar "gap" in their aggregate half-lives, such that no fission products have

1664-483: A lightly enriched uranium, criticality could be reached. This experiment was the first practical step toward the light-water reactor. After World War II and with the availability of enriched uranium, new reactor concepts became feasible. In 1946, Eugene Wigner and Alvin Weinberg proposed and developed the concept of a reactor using enriched uranium as a fuel, and light water as a moderator and coolant. This concept

1768-632: A material full of atoms with light nuclei which do not easily absorb neutrons. The neutrons strike the nuclei and bounce off. After sufficient impacts, the velocity of the neutron will be comparable to the thermal velocities of the nuclei; this neutron is then called a thermal neutron. The light-water reactor uses ordinary water , also called light water, as its neutron moderator. The light water absorbs too many neutrons to be used with unenriched natural uranium, and therefore uranium enrichment or nuclear reprocessing becomes necessary to operate such reactors, increasing overall costs. This differentiates it from

1872-475: A moderator. By the end of the war , following an idea of Alvin Weinberg , natural uranium fuel elements were arranged in a lattice in ordinary water at the top of the X10 reactor to evaluate the neutron multiplication factor. The purpose of this experiment was to determine the feasibility of a nuclear reactor using light water as a moderator and coolant, and clad solid uranium as fuel. The results showed that, with

1976-479: A prototype. Light-water reactor The light-water reactor ( LWR ) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water , as both its coolant and neutron moderator ; furthermore a solid form of fissile elements is used as fuel. Thermal-neutron reactors are the most common type of nuclear reactor , and light-water reactors are the most common type of thermal-neutron reactor. There are three varieties of light-water reactors:

2080-432: A reactor moderator and coolant, but the vast majority of Russian nuclear-powered boats and ships use light-water reactors exclusively. The reason for near exclusive LWR use aboard nuclear naval vessels is the level of inherent safety built into these types of reactors. Since light water is used as both a coolant and a neutron moderator in these reactors, if one of these reactors suffers damage due to military action, leading to

2184-419: A reactor's performance is the "conversion ratio", defined as the ratio of new fissile atoms produced to fissile atoms consumed. All proposed nuclear reactors except specially designed and operated actinide burners experience some degree of conversion. As long as there is any amount of a fertile material within the neutron flux of the reactor, some new fissile material is always created. When the conversion ratio

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2288-592: A third of the world's thorium reserves are in India, which lacks significant uranium reserves. The third and final core of the Shippingport Atomic Power Station 60 MWe reactor was a light water thorium breeder, which began operating in 1977. It used pellets made of thorium dioxide and uranium-233 oxide; initially, the U-233 content of the pellets was 5–6% in the seed region, 1.5–3% in

2392-566: A thorium thermal breeder. Liquid-fluoride reactors may have attractive features, such as inherent safety, no need to manufacture fuel rods, and possibly simpler reprocessing of the liquid fuel. This concept was first investigated at the Oak Ridge National Laboratory Molten-Salt Reactor Experiment in the 1960s. From 2012 it became the subject of renewed interest worldwide. Breeder reactors could, in principle, extract almost all of

2496-465: Is a nuclear reactor that generates more fissile material than it consumes. These reactors can be fueled with more-commonly available isotopes of uranium and thorium , such as uranium-238 and thorium-232 , as opposed to the rare uranium-235 which is used in conventional reactors. These materials are called fertile materials since they can be bred into fuel by these breeder reactors. Breeder reactors achieve this because their neutron economy

2600-527: Is an unpressurized area, and the reactor core has not yet been breached (as of June 2006). The reason for renewed interest in the FFTF is that the global atmosphere with regard to nuclear energy has changed , and the US is pursuing nuclear power once again. To build a similar facility would cost an estimated $ 2–5 billion. In April, 2006, the FFTF was honored by the American Nuclear Society as

2704-450: Is boiled directly by the reactor core, for example the boiling-water reactor. Many other reactors are also light-water cooled, notably the RBMK and some military plutonium -production reactors. These are not regarded as LWRs, as they are moderated by graphite , and as a result their nuclear characteristics are very different. Although the coolant flow rate in commercial PWRs is constant, it

2808-400: Is circulated past the reactor core to absorb the heat that it generates. The heat is carried away from the reactor and is then used to generate steam. Most reactor systems employ a cooling system that is physically separate from the water that will be boiled to produce pressurized steam for the turbines , like the pressurized-water reactor. But in some reactors the water for the steam turbines

2912-418: Is consumed in the reactor. Light-water reactors are generally refueled every 12 to 18 months, at which time, about 25 percent of the fuel is replaced. The enriched UF 6 is converted into uranium dioxide powder that is then processed into pellet form. The pellets are then fired in a high-temperature, sintering furnace to create hard, ceramic pellets of enriched uranium . The cylindrical pellets then undergo

3016-564: Is due to the nation's large reserves, though known worldwide reserves of thorium are four times those of uranium. India's Department of Atomic Energy said in 2007 that it would simultaneously construct four more breeder reactors of 500 MWe each including two at Kalpakkam . BHAVINI , an Indian nuclear power company, was established in 2003 to construct, commission, and operate all stage II fast breeder reactors outlined in India's three-stage nuclear power programme . To advance these plans,

3120-403: Is enough fuel for breeder reactors to satisfy the world's energy needs for 5 billion years at 1983's total energy consumption rate, thus making nuclear energy effectively a renewable energy . In addition to seawater, the average crustal granite rocks contain significant quantities of uranium and thorium that with breeder reactors can supply abundant energy for the remaining lifespan of the sun on

3224-691: Is formed into pellets and inserted into zirconium alloy tubes that are bundled together. The zirconium alloy tubes are about 1 cm in diameter, and the fuel cladding gap is filled with helium gas to improve the conduction of heat from the fuel to the cladding. There are about 179-264 fuel rods per fuel bundle and about 121 to 193 fuel bundles are loaded into a reactor core . Generally, the fuel bundles consist of fuel rods bundled 14x14 to 17x17. PWR fuel bundles are about 4 meters in length. The zirconium alloy tubes are pressurized with helium to try to minimize pellet cladding interaction which can lead to fuel rod failure over long periods. In boiling water reactors,

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3328-457: Is greater than 1, it is often called the "breeding ratio". For example, commonly used light water reactors have a conversion ratio of approximately 0.6. Pressurized heavy-water reactors running on natural uranium have a conversion ratio of 0.8. In a breeder reactor, the conversion ratio is higher than 1. "Break-even" is achieved when the conversion ratio reaches 1.0 and the reactor produces as much fissile material as it uses. The doubling time

3432-438: Is high enough to create more fissile fuel than they use. These extra neutrons are absorbed by the fertile material that is loaded into the reactor along with fissile fuel. This irradiated fertile material in turn transmutes into fissile material which can undergo fission reactions . Breeders were at first found attractive because they made more complete use of uranium fuel than light-water reactors , but interest declined after

3536-469: Is not in nuclear reactors used on U.S. Navy ships. The use of ordinary water makes it necessary to do a certain amount of enrichment of the uranium fuel before the necessary criticality of the reactor can be maintained. The light-water reactor uses uranium 235 as a fuel, enriched to approximately 3 percent. Although this is its major fuel, the uranium 238 atoms also contribute to the fission process by converting to plutonium 239 ; about one-half of which

3640-640: Is stated on the site dedicated to the FFTF, that it tested "advanced nuclear fuels , materials, components , nuclear power plant operations and maintenance protocols, and reactor safety designs." By 1993, the number of uses to which the reactor could be put was diminishing, so the decision was taken in December of that year to deactivate it. Over the next three years, the active parts of the facility were gradually halted, fuel rods removed and stored in above-ground dry storage vessels . However, in January 1997,

3744-440: Is the amount of time it would take for a breeder reactor to produce enough new fissile material to replace the original fuel and additionally produce an equivalent amount of fuel for another nuclear reactor. This was considered an important measure of breeder performance in early years, when uranium was thought to be scarce. However, since uranium is more abundant than thought in the early days of nuclear reactor development, and given

3848-445: Is transuranics (atoms heavier than uranium), which are generated from uranium or heavier atoms in the fuel when they absorb neutrons but do not undergo fission. All transuranic isotopes fall within the actinide series on the periodic table , and so they are frequently referred to as the actinides. The largest component is the remaining uranium which is around 98.25% uranium-238, 1.1% uranium-235, and 0.65% uranium-236. The U-236 comes from

3952-400: The activity of the waste is about the same as that produced by a light-water reactor. Waste from a breeder reactor has a different decay behavior because it is made up of different materials. Breeder reactor waste is mostly fission products, while light-water reactor waste is mostly unused uranium isotopes and a large quantity of transuranics. After spent nuclear fuel has been removed from

4056-531: The BN-600 reactor , at 560 MWe, and the BN-800 reactor , at 880 MWe. Both are Russian sodium-cooled reactors. The designs use liquid metal as the primary coolant, to transfer heat from the core to steam used to power the electricity generating turbines. FBRs have been built cooled by liquid metals other than sodium—some early FBRs used mercury ; other experimental reactors have used a sodium-potassium alloy . Both have

4160-476: The Chinese Academy of Sciences annual conference in 2011. Its ultimate target was to investigate and develop a thorium-based molten salt nuclear system over about 20 years. South Korea is developing a design for a standardized modular FBR for export, to complement the standardized pressurized water reactor and CANDU designs they have already developed and built, but has not yet committed to building

4264-482: The Energy Impact Center announced publication of an open-sourced engineering design of a pressurized water reactor capable of producing 300 MWth/100 MWe of energy called OPEN100 . The family of nuclear reactors known as light-water reactors (LWR), cooled and moderated using ordinary water, tend to be simpler and cheaper to build than other types of nuclear reactors ; due to these factors, they make up

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4368-453: The FBR-600 is a pool-type sodium-cooled reactor with a rating of 600 MWe. The China Experimental Fast Reactor is a 25 MW(e) prototype for the planned China Prototype Fast Reactor. It started generating power in 2011. China initiated a research and development project in thorium molten-salt thermal breeder-reactor technology (liquid fluoride thorium reactor), formally announced at

4472-607: The Idaho National Laboratory ) in a series of tests called the BORAX experiments . PIUS, standing for Process Inherent Ultimate Safety , was a Swedish design designed by ASEA-ATOM. It is a concept for a light-water reactor system. Along with the SECURE reactor, it relied on passive measures, not requiring operator actions or external energy supplies, to provide safe operation. No units were ever built. In 2020,

4576-630: The International Panel on Fissile Materials said "After six decades and the expenditure of the equivalent of tens of billions of dollars, the promise of breeder reactors remains largely unfulfilled and efforts to commercialize them have been steadily cut back in most countries". In Germany, the United Kingdom, and the United States, breeder reactor development programs have been abandoned. The rationale for pursuing breeder reactors—sometimes explicit and sometimes implicit—was based on

4680-406: The boiling water reactor , the heat generated by fission turns the water into steam, which directly drives the power-generating turbines. But in the pressurized water reactor , the heat generated by fission is transferred to a secondary loop via a heat exchanger. Steam is produced in the secondary loop, and the secondary loop drives the power-generating turbines. In either case, after flowing through

4784-417: The pressurized water reactor (PWR), the boiling water reactor (BWR), and (most designs of) the supercritical water reactor (SCWR). After the discoveries of fission , moderation and of the theoretical possibility of a nuclear chain reaction , early experimental results rapidly showed that natural uranium could only undergo a sustained chain reaction using graphite or heavy water as a moderator. While

4888-479: The supercritical water reactor (SCWR) has sufficient heat capacity to allow adequate cooling with less water, making a fast-spectrum water-cooled reactor a practical possibility. The type of coolants, temperatures, and fast neutron spectrum puts the fuel cladding material (normally austenitic stainless or ferritic-martensitic steels) under extreme conditions. The understanding of the radiation damage, coolant interactions, stresses, and temperatures are necessary for

4992-407: The 1960s as more uranium reserves were found and new methods of uranium enrichment reduced fuel costs. Many types of breeder reactor are possible: A "breeder" is simply a nuclear reactor designed for very high neutron economy with an associated conversion rate higher than 1.0. In principle, almost any reactor design could be tweaked to become a breeder. For example, the light-water reactor ,

5096-551: The DOE ordered that the reactor be maintained in a standby condition, pending a decision as to whether to incorporate it into the US Government's tritium production program, for both medical and fusion research. Since then, due to legal wrangling, decommissioning has been stopped and restarted at intervals. In December 2001, the deactivation was continued, after the DOE found that it was not needed for tritium production. Work

5200-865: The Koreans currently designing and constructing their second generation of indigenous designs. The leaders in national experience with BWRs, offering reactors for export, are the United States and Japan, with the alliance of General Electric (of the US) and Hitachi (of Japan), offering both the Advanced Boiling Water Reactor (ABWR) and the Economic Simplified Boiling Water Reactor (ESBWR) for construction and export; in addition, Toshiba offers an ABWR variant for construction in Japan, as well. West Germany

5304-559: The Low Intensity Test Reactor (LITR), reached criticality on February 4, 1950 and was the world's first light-water reactor. Immediately after the end of World War II the United States Navy started a program under the direction of Captain (later Admiral) Hyman Rickover , with the goal of nuclear propulsion for ships. It developed the first pressurized water reactors in the early 1950s, and led to

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5408-786: The Republic of France (offering the AREVA EPR for export), and Japan (offering the Mitsubishi Advanced Pressurized Water Reactor for export); in addition, both the People's Republic of China and the Republic of Korea are both noted to be rapidly ascending into the front rank of PWR-constructing nations as well, with the Chinese being engaged in a massive program of nuclear power expansion, and

5512-480: The Russian Federation and former Soviet states. Though electricity generation capabilities are comparable between all these types of reactor, due to the aforementioned features, and the extensive experience with operations of the LWR, it is favored in the vast majority of new nuclear power plants. In addition, light-water reactors make up the vast majority of reactors that power naval nuclear-powered vessels . Four out of

5616-548: The Soviet BN-350 liquid-metal-cooled reactor. Theoretical models of breeders with liquid sodium coolant flowing through tubes inside fuel elements ("tube-in-shell" construction) suggest breeding ratios of at least 1.8 are possible on an industrial scale. The Soviet BR-1 test reactor achieved a breeding ratio of 2.5 under non-commercial conditions. Fission of the nuclear fuel in any reactor unavoidably produces neutron-absorbing fission products . The fertile material from

5720-458: The actinide wastes as fuel and thus convert them to more fission products. After spent nuclear fuel is removed from a light water reactor, it undergoes a complex decay profile as each nuclide decays at a different rate. There is a large gap in the decay half-lives of fission products compared to transuranic isotopes. If the transuranics are left in the spent fuel, after 1,000 to 100,000 years the slow decay of these transuranics would generate most of

5824-406: The advantage that they are liquids at room temperature, which is convenient for experimental rigs but less important for pilot or full-scale power stations. Three of the proposed generation IV reactor types are FBRs: FBRs usually use a mixed oxide fuel core of up to 20% plutonium dioxide (PuO 2 ) and at least 80% uranium dioxide (UO 2 ). Another fuel option is metal alloys , typically

5928-428: The amount of plutonium available in spent reactor fuel, doubling time has become a less important metric in modern breeder-reactor design. " Burnup " is a measure of how much energy has been extracted from a given mass of heavy metal in fuel, often expressed (for power reactors) in terms of gigawatt-days per ton of heavy metal. Burnup is an important factor in determining the types and abundances of isotopes produced by

6032-414: The blanket region, and none in the reflector region. It operated at 236 MWt, generating 60 MWe, and ultimately produced over 2.1 billion kilowatt hours of electricity. After five years, the core was removed and found to contain nearly 1.4% more fissile material than when it was installed, demonstrating that breeding from thorium had occurred. A liquid fluoride thorium reactor is also planned as

6136-497: The breeder-reactor fuel cycle posed an even greater proliferation concern because they would use PUREX to separate plutonium in a highly attractive isotopic form for use in nuclear weapons. Several countries are developing reprocessing methods that do not separate the plutonium from the other actinides. For instance, the non-water-based pyrometallurgical electrowinning process, when used to reprocess fuel from an integral fast reactor , leaves large amounts of radioactive actinides in

6240-469: The chain reaction to slow down, producing less heat. This property, known as the negative temperature coefficient of reactivity, makes PWRs very stable. In event of a loss-of-coolant accident , the moderator is also lost and the active fission reaction will stop. Heat is still produced after the chain reaction stops from the radioactive byproducts of fission, at about 5% of rated power. This "decay heat" will continue for 1 to 3 years after shut down, whereupon

6344-415: The control rods are lowered into the core, they absorb neutrons, which thus cannot take part in the chain reaction . On the converse, when the control rods are lifted out of the way, more neutrons strike the fissile uranium-235 or plutonium-239 nuclei in nearby fuel rods, and the chain reaction intensifies. All of this is enclosed in a water-filled steel pressure vessel , called the reactor vessel . In

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6448-424: The core are required to cool the reactor, the yield of neutrons and therefore breeding of Pu are strongly affected. Theoretical work has been done on reduced moderation water reactors , which may have a sufficiently fast spectrum to provide a breeding ratio slightly over 1. This would likely result in an unacceptable power derating and high costs in a liquid-water-cooled reactor, but the supercritical water coolant of

6552-532: The core to allow a chain reaction to occur. The number of control rods inserted and the distance by which they are inserted can be varied to control the reactivity of the reactor. Usually there are also other means of controlling reactivity. In the PWR design a soluble neutron absorber, usually boric acid , is added to the reactor coolant allowing the complete extraction of the control rods during stationary power operation ensuring an even power and flux distribution over

6656-493: The energy contained in uranium or thorium, decreasing fuel requirements by a factor of 100 compared to widely used once-through light water reactors, which extract less than 1% of the energy in the actinide metal (uranium or thorium) mined from the earth. The high fuel-efficiency of breeder reactors could greatly reduce concerns about fuel supply, energy used in mining, and storage of radioactive waste. With seawater uranium extraction (currently too expensive to be economical), there

6760-500: The entire core. Operators of the BWR design use the coolant flow through the core to control reactivity by varying the speed of the reactor recirculation pumps. An increase in the coolant flow through the core improves the removal of steam bubbles, thus increasing the density of the coolant/moderator with the result of decreasing power. The light-water reactor also uses ordinary water to keep the reactor cooled. The cooling source, light water,

6864-426: The fertile material in the uranium fuel cycle has an atomic weight of 238. That mass difference means that thorium-232 requires six more neutron capture events per nucleus before the transuranic elements can be produced. In addition to this simple mass difference, the reactor gets two chances to fission the nuclei as the mass increases: First as the effective fuel nuclei U233, and as it absorbs two more neutrons, again as

6968-748: The five great powers with nuclear naval propulsion capacity use light-water reactors exclusively: the British Royal Navy , the Chinese People's Liberation Army Navy , the French Marine nationale , and the United States Navy . Only the Russian Federation's Navy has used a relative handful of liquid-metal cooled reactors in production vessels, specifically the Alfa class submarine , which used lead-bismuth eutectic as

7072-428: The following key assumptions: Some past anti-nuclear advocates have become pro-nuclear power as a clean source of electricity since breeder reactors effectively recycle most of their waste. This solves one of the most-important negative issues of nuclear power. In the documentary Pandora's Promise , a case is made for breeder reactors because they provide a real high-kW alternative to fossil fuel energy. According to

7176-423: The fuel is similar to PWR fuel except that the bundles are "canned"; that is, there is a thin tube surrounding each bundle. This is primarily done to prevent local density variations from affecting neutronics and thermal hydraulics of the nuclear core on a global scale. In modern BWR fuel bundles, there are either 91, 92, or 96 fuel rods per assembly depending on the manufacturer. A range between 368 assemblies for

7280-474: The fuel nuclei U235. A reactor whose main purpose is to destroy actinides rather than increasing fissile fuel-stocks is sometimes known as a burner reactor . Both breeding and burning depend on good neutron economy, and many designs can do either. Breeding designs surround the core by a breeding blanket of fertile material. Waste burners surround the core with non-fertile wastes to be destroyed. Some designs add neutron reflectors or absorbers. One measure of

7384-573: The fuel such a 1 gigawatt reactor would need. Such self-contained breeders are currently envisioned as the final self-contained and self-supporting ultimate goal of nuclear reactor designers. The project was canceled in 1994 by United States Secretary of Energy Hazel O'Leary . The first fast reactor built and operated was the Los Alamos Plutonium Fast Reactor (" Clementine ") in Los Alamos, NM. Clementine

7488-447: The geometry of the fuel (which also contains uranium-238), arranged to attain sufficient fast neutron capture. The plutonium-239 (or the fissile uranium-235) fissile cross-section is much smaller in a fast spectrum than in a thermal spectrum, as is the ratio between the Pu/ U fission cross-section and the U absorption cross-section. This increases the concentration of Pu/ U needed to sustain

7592-426: The long term. Germany, in contrast, abandoned the technology due to safety concerns. The SNR-300 fast breeder reactor was finished after 19 years despite cost overruns summing up to a total of € 3.6 billion, only to then be abandoned. The advanced heavy-water reactor is one of the few proposed large-scale uses of thorium. India is developing this technology, motivated by substantial thorium reserves; almost

7696-490: The main sequence of stellar evolution. No fission products have a half-life in the range of 100 a–210 ka ... ... nor beyond 15.7 Ma In broad terms, spent nuclear fuel has three main components. The first consists of fission products , the leftover fragments of fuel atoms after they have been split to release energy. Fission products come in dozens of elements and hundreds of isotopes, all of them lighter than uranium. The second main component of spent fuel

7800-416: The minor actinides (neptunium, americium, curium, etc.). Since breeder reactors on a closed fuel cycle would use nearly all of the isotopes of these actinides fed into them as fuel, their fuel requirements would be reduced by a factor of about 100. The volume of waste they generate would be reduced by a factor of about 100 as well. While there is a huge reduction in the volume of waste from a breeder reactor,

7904-403: The movie, one pound of uranium provides as much energy as 5,000 barrels of oil . The Soviet Union constructed a series of fast reactors, the first being mercury-cooled and fueled with plutonium metal, and the later plants sodium-cooled and fueled with plutonium oxide. BR-1 (1955) was 100W (thermal) was followed by BR-2 at 100 kW and then the 5 MW BR-5. BOR-60 (first criticality 1969)

8008-448: The non-fission capture reaction where U-235 absorbs a neutron but releases only a high energy gamma ray instead of undergoing fission. The physical behavior of the fission products is markedly different from that of the actinides. In particular, fission products do not undergo fission and therefore cannot be used as nuclear fuel. Indeed, because fission products are often neutron poisons (absorbing neutrons that could be used to sustain

8112-564: The nuclear fuel core of a power reactor. The metal used for the tubes depends on the design of the reactor – stainless steel was used in the past, but most reactors now use a zirconium alloy . For the most common types of reactors the tubes are assembled into bundles with the tubes spaced precise distances apart. These bundles are then given a unique identification number, which enables them to be tracked from manufacture through use and into disposal. Pressurized water reactor fuel consists of cylindrical rods put into bundles. A uranium oxide ceramic

8216-513: The portion of a nuclear reactor where the nuclear reactions take place. It mainly consists of nuclear fuel and control elements . The pencil-thin nuclear fuel rods, each about 12 feet (3.7 m) long, are grouped by the hundreds in bundles called fuel assemblies. Inside each fuel rod, pellets of uranium , or more commonly uranium oxide , are stacked end to end. The control elements, called control rods, are filled with pellets of substances like hafnium or cadmium that readily capture neutrons. When

8320-507: The power produced by commercial nuclear reactors comes from fission of plutonium generated within the fuel. Even with this level of plutonium consumption, light water reactors consume only part of the plutonium and minor actinides they produce, and nonfissile isotopes of plutonium build up, along with significant quantities of other minor actinides. Breeding fuel cycles attracted renewed interest because of their potential to reduce actinide wastes, particularly various isotopes of plutonium and

8424-529: The protactinium remains in the reactor, small amounts of uranium-232 are also produced, which has the strong gamma emitter thallium-208 in its decay chain. Similar to uranium-fueled designs, the longer the fuel and fertile material remain in the reactor, the more of these undesirable elements build up. In the envisioned commercial thorium reactors , high levels of uranium-232 would be allowed to accumulate, leading to extremely high gamma-radiation doses from any uranium derived from thorium. These gamma rays complicate

8528-453: The radioactivity in that spent fuel. Thus, removing the transuranics from the waste eliminates much of the long-term radioactivity of spent nuclear fuel. Today's commercial light-water reactors do breed some new fissile material, mostly in the form of plutonium. Because commercial reactors were never designed as breeders, they do not convert enough uranium-238 into plutonium to replace the uranium-235 consumed. Nonetheless, at least one-third of

8632-434: The reactor finally reaches "full cold shutdown". Decay heat, while dangerous and strong enough to melt the core, is not nearly as intense as an active fission reaction. During the post shutdown period the reactor requires cooling water to be pumped or the reactor will overheat. If the temperature exceeds 2200 °C, cooling water will break down into hydrogen and oxygen, which can form a (chemically) explosive mixture. Decay heat

8736-418: The reactor fuel. More conventional water-based reprocessing systems include SANEX, UNEX, DIAMEX, COEX, and TRUEX, and proposals to combine PUREX with those and other co-processes. All these systems have moderately better proliferation resistance than PUREX, though their adoption rate is low. In the thorium cycle, thorium-232 breeds by converting first to protactinium-233, which then decays to uranium-233. If

8840-501: The reactor. This process is an obvious chemical operation which is not required for normal operation of these reactor designs, but it could feasibly happen beyond the oversight of organizations such as the International Atomic Energy Agency (IAEA), and thus must be safeguarded against. Like many aspects of nuclear power, fast breeder reactors have been subject to much controversy over the years. In 2010

8944-508: The safe handling of a weapon and the design of its electronics; this explains why uranium-233 has never been pursued for weapons beyond proof-of-concept demonstrations. While the thorium cycle may be proliferation-resistant with regard to uranium-233 extraction from fuel (because of the presence of uranium-232), it poses a proliferation risk from an alternate route of uranium-233 extraction, which involves chemically extracting protactinium-233 and allowing it to decay to pure uranium-233 outside of

9048-408: The safe operation of any reactor core. All materials used to date in sodium-cooled fast reactors have known limits. Oxide dispersion-strengthened alloy steel is viewed as the long-term radiation resistant fuel-cladding material that can overcome the shortcomings of today's material choices. One design of fast neutron reactor, specifically conceived to address the waste disposal and plutonium issues,

9152-519: The salt carrier with heavier metal chlorides (e.g., KCl, RbCl, ZrCl 4 ). Several prototype FBRs have been built, ranging in electrical output from a few light bulbs' equivalent ( EBR-I , 1951) to over 1,000  MWe . As of 2006, the technology is not economically competitive to thermal reactor technology, but India , Japan, China, South Korea, and Russia are all committing substantial research funds to further development of fast breeder reactors, anticipating that rising uranium prices will change this in

9256-431: The site of the breeder reactor. Breeder reactors incorporating such technology would most likely be designed with breeding ratios very close to 1.00, so that after an initial loading of enriched uranium and/or plutonium fuel, the reactor would then be refueled only with small deliveries of natural uranium . A quantity of natural uranium equivalent to a block about the size of a milk crate delivered once per month would be all

9360-401: The smallest and 800 assemblies for the largest U.S. BWR forms the reactor core. Each BWR fuel rod is back filled with helium to a pressure of about three atmospheres (300 kPa). A neutron moderator is a medium which reduces the velocity of fast neutrons , thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235. A good neutron moderator is

9464-647: The successful deployment of the first nuclear submarine, the USS ; Nautilus  (SSN-571) . The Soviet Union independently developed a version of the PWR in the late 1950s, under the name of VVER . While functionally very similar to the American effort, it also has certain design distinctions from Western PWRs. Researcher Samuel Untermyer II led the effort to develop the BWR at the US National Reactor Testing Station (now

9568-498: The transuranics in the final waste stream, this advantage would be greatly reduced. The FBR's fast neutrons can fission actinide nuclei with even numbers of both protons and neutrons. Such nuclei usually lack the low-speed "thermal neutron" resonances of fissile fuels used in LWRs. The thorium fuel cycle inherently produces lower levels of heavy actinides. The fertile material in the thorium fuel cycle has an atomic weight of 232, while

9672-557: The turbines, the steam turns back into water in the condenser. The water required to cool the condenser is taken from a nearby river or ocean. It is then pumped back into the river or ocean, in warmed condition. The heat can also be dissipated via a cooling tower into the atmosphere. The United States uses LWR reactors for electric power production, in comparison to the heavy water reactors used in Canada. Control rods are usually combined into control rod assemblies — typically 20 rods for

9776-477: The vast majority of civil nuclear reactors and naval propulsion reactors in service throughout the world as of 2009. LWRs can be subdivided into three categories – pressurized water reactors (PWRs), boiling water reactors (BWRs), and supercritical water reactors ( SCWRs ). The SCWR remains hypothetical as of 2009; it is a Generation IV design that is still a light-water reactor, but it is only partially moderated by light water and exhibits certain characteristics of

9880-479: The waste. Some of these fission products could later be separated for industrial or medical uses and the rest sent to a waste repository. The IFR pyroprocessing system uses molten cadmium cathodes and electrorefiners to reprocess metallic fuel directly on-site at the reactor. Such systems co-mingle all the minor actinides with both uranium and plutonium. The systems are compact and self-contained, so that no plutonium-containing material needs to be transported away from

9984-419: The water is denser, because more collisions will occur. The use of water as a moderator is an important safety feature of PWRs, as any increase in temperature causes the water to expand and become less dense; thereby reducing the extent to which neutrons are slowed down and hence reducing the reactivity in the reactor. Therefore, if reactivity increases beyond normal, the reduced moderation of neutrons will cause

10088-473: The world's first reactors ( CP-1 , X10 etc.) were successfully reaching criticality , uranium enrichment began to develop from theoretical concept to practical applications in order to meet the goal of the Manhattan Project , to build a nuclear explosive . In May 1944, the first grams of enriched uranium ever produced reached criticality in the low power (LOPO) reactor at Los Alamos , which

10192-506: Was 60 MW, with construction started in 1965. India has been trying to develop fast breeder reactors for decades but suffered repeated delays. By December 2024 the Prototype Fast Breeder Reactor is due to be completed and commissioned. The program is intended to use fertile thorium-232 to breed fissile uranium-233. India is also pursuing thorium thermal breeder reactor technology. India's focus on thorium

10296-477: Was also once a major player with BWRs. The other types of nuclear reactor in use for power generation are the heavy water moderated reactor , built by Canada ( CANDU ) and the Republic of India (AHWR), the advanced gas cooled reactor (AGCR), built by the United Kingdom, the liquid metal cooled reactor (LMFBR), built by the Russian Federation, the Republic of France, and Japan, and the graphite-moderated, water-cooled reactor (RBMK or LWGR), found exclusively within

10400-424: Was fueled by Ga-stabilized delta-phase Pu and cooled with mercury. It contained a 'window' of Th-232 in anticipation of breeding experiments, but no reports were made available regarding this feature. Another proposed fast reactor is a fast molten salt reactor , in which the molten salt's moderating properties are insignificant. This is typically achieved by replacing the light metal fluorides (e.g. LiF, BeF 2 ) in

10504-475: Was halted in 2002 when court action was begun. As of May 2003, deactivation has continued, and it is currently in a state of cold standby . In May 2005 the core support basket was drilled to drain the remaining sodium coolant, which effectively made the reactor unusable. However, a technical study is being pursued with regard to repairing the reactor. As the coolant was drained, the system was filled with high purity argon gas to prevent corrosion. The support basket

10608-645: Was proposed for a reactor whose purpose was to test the behavior of materials under neutron flux . This reactor, the Material Testing Reactor (MTR) , was built in Idaho at INL and reached criticality on March 31, 1952. For the design of this reactor, experiments were necessary, so a mock-up of the MTR was built at ORNL , to assess the hydraulic performances of the primary circuit and then to test its neutronic characteristics. This MTR mock-up, later called

10712-477: Was the integral fast reactor (IFR, also known as an integral fast breeder reactor, although the original reactor was designed to not breed a net surplus of fissile material). To solve the waste disposal problem, the IFR had an on-site electrowinning fuel-reprocessing unit that recycled the uranium and all the transuranics (not just plutonium) via electroplating , leaving just short- half-life fission products in

10816-421: Was used to estimate the critical mass of U235 to produce the atomic bomb. LOPO cannot be considered as the first light-water reactor because its fuel was not a solid uranium compound cladded with corrosion-resistant material, but was composed of uranyl sulfate salt dissolved in water. It is however the first aqueous homogeneous reactor and the first reactor using enriched uranium as fuel and ordinary water as

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