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85-484: Before SRP can begin, the vessel's nuclear fuel must be removed, and defueling usually coincides with decommissioning . Until the fuel is removed, the vessel is referred to as "USS Name ," but afterward, the "USS" prefix is dropped and it is referred to as "ex- Name ." Reusable equipment is removed at the same time as the fuel. Spent nuclear fuel is shipped by rail to the Naval Reactor Facility in

170-589: A commercial shipyard. As of November 2024, the hull remains stored at Hampton Roads . † A dagger after a completion date indicates that portions of the hull were preserved as memorials. See the individual articles for details. (note) ex- Long Beach has been partially dismantled and remains moored in Puget Sound Naval Shipyard in 2018. Some of these submarines (the George Washington class) were fleet ballistic missile boats for

255-422: A completion date indicates that portions of the hull were preserved as memorials. See the individual articles for details. Because the program is underway, this list is almost certainly incomplete. Note for ships marked with refit : Sam Rayburn (SSBN-635) was converted into a training platform – Moored Training Ship (MTS-635). Sam Rayburn arrived for conversion on 1 February 1986, and on 29 July 1989

340-406: A dense solid which has few pores. The thermal conductivity of uranium dioxide is very low compared with that of zirconium metal, and it goes down as the temperature goes up. Corrosion of uranium dioxide in water is controlled by similar electrochemical processes to the galvanic corrosion of a metal surface. While exposed to the neutron flux during normal operation in the core environment,

425-432: A fuel would be so expensive it is likely that the fuel would require pyroprocessing to enable recovery of the N. It is likely that if the fuel was processed and dissolved in nitric acid that the nitrogen enriched with N would be diluted with the common N. Fluoride volatility is a method of reprocessing that does not rely on nitric acid, but it has only been demonstrated in relatively small scale installations whereas

510-453: A kernel of UO X fuel (sometimes UC or UCO), which has been coated with four layers of three isotropic materials deposited through fluidized chemical vapor deposition (FCVD). The four layers are a porous buffer layer made of carbon that absorbs fission product recoils, followed by a dense inner layer of protective pyrolytic carbon (PyC), followed by a ceramic layer of SiC to retain fission products at elevated temperatures and to give

595-624: A properly designed reactor. Two such reactor designs are the prismatic-block gas-cooled reactor (such as the GT-MHR ) and the pebble-bed reactor (PBR). Both of these reactor designs are high temperature gas reactors (HTGRs). These are also the basic reactor designs of very-high-temperature reactors (VHTRs), one of the six classes of reactor designs in the Generation IV initiative that is attempting to reach even higher HTGR outlet temperatures. TRISO fuel particles were originally developed in

680-768: A reactor is plutonium, and some two thirds of this is fissile (c. 50% Pu , 15% Pu ). Metal fuels have the advantage of a much higher heat conductivity than oxide fuels but cannot survive equally high temperatures. Metal fuels have a long history of use, stretching from the Clementine reactor in 1946 to many test and research reactors. Metal fuels have the potential for the highest fissile atom density. Metal fuels are normally alloyed, but some metal fuels have been made with pure uranium metal. Uranium alloys that have been used include uranium aluminum, uranium zirconium , uranium silicon, uranium molybdenum, uranium zirconium hydride (UZrH), and uranium zirconium carbonitride. Any of

765-867: A similar design to the CANDU but built by German KWU was originally designed for non-enriched fuel but since switched to slightly enriched fuel with a U content about 0.1 percentage points higher than in natural uranium. Various other nuclear fuel forms find use in specific applications, but lack the widespread use of those found in BWRs, PWRs, and CANDU power plants. Many of these fuel forms are only found in research reactors, or have military applications. Magnox (magnesium non-oxidising) reactors are pressurised, carbon dioxide –cooled, graphite - moderated reactors using natural uranium (i.e. unenriched) as fuel and Magnox alloy as fuel cladding. Working pressure varies from 6.9 to 19.35 bars (100.1 to 280.6 psi) for

850-452: A small percentage of the U in the fuel absorbs excess neutrons and is transmuted into U . U rapidly decays into Np which in turn rapidly decays into Pu . The small percentage of Pu has a higher neutron cross section than U . As the Pu accumulates the chain reaction shifts from pure U at initiation of the fuel use to a ratio of about 70% U and 30% Pu at the end of

935-409: A solid called ammonium diuranate , (NH 4 ) 2 U 2 O 7 . This is then heated ( calcined ) to form UO 3 and U 3 O 8 which is then converted by heating with hydrogen or ammonia to form UO 2 . The UO 2 is mixed with an organic binder and pressed into pellets. The pellets are then fired at a much higher temperature (in hydrogen or argon) to sinter the solid. The aim is to form

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1020-476: A typical core loading is on the order of 4500–6500 bundles, depending on the design. Modern types typically have 37 identical fuel pins radially arranged about the long axis of the bundle, but in the past several different configurations and numbers of pins have been used. The CANFLEX bundle has 43 fuel elements, with two element sizes. It is also about 10 cm (4 inches) in diameter, 0.5 m (20 in) long and weighs about 20 kg (44 lb) and replaces

1105-399: A typical spent fuel assembly still exceeds 10,000 rem/hour, resulting in a fatal dose in just minutes. Two main modes of release exist, the fission products can be vaporised or small particles of the fuel can be dispersed. Post-Irradiation Examination (PIE) is the study of used nuclear materials such as nuclear fuel. It has several purposes. It is known that by examination of used fuel that

1190-404: A way as to ensure low contamination with non-radioactive carbon (not a common fission product and absent in nuclear reactors that don't use it as a moderator ) then fluoride volatility could be used to separate the C produced by producing carbon tetrafluoride . C is proposed for use in particularly long lived low power nuclear batteries called diamond batteries . Much of what

1275-730: Is a means to dispose of surplus plutonium by transmutation . Reprocessing of commercial nuclear fuel to make MOX was done in the Sellafield MOX Plant (England). As of 2015, MOX fuel is made in France at the Marcoule Nuclear Site , and to a lesser extent in Russia at the Mining and Chemical Combine , India and Japan. China plans to develop fast breeder reactors and reprocessing. The Global Nuclear Energy Partnership

1360-475: Is able to release xenon gas, which normally acts as a neutron absorber ( Xe is the strongest known neutron poison and is produced both directly and as a decay product of I as a fission product ) and causes structural occlusions in solid fuel elements (leading to the early replacement of solid fuel rods with over 98% of the nuclear fuel unburned, including many long-lived actinides). In contrast, molten-salt reactors are capable of retaining

1445-498: Is commonly composed of enriched uranium sandwiched between metal cladding. Plate-type fuel is used in several research reactors where a high neutron flux is desired, for uses such as material irradiation studies or isotope production, without the high temperatures seen in ceramic, cylindrical fuel. It is currently used in the Advanced Test Reactor (ATR) at Idaho National Laboratory , and the nuclear research reactor at

1530-410: Is compacted to cylindrical pellets and sintered at high temperatures to produce ceramic nuclear fuel pellets with a high density and well defined physical properties and chemical composition. A grinding process is used to achieve a uniform cylindrical geometry with narrow tolerances. Such fuel pellets are then stacked and filled into the metallic tubes. The metal used for the tubes depends on the design of

1615-596: Is done is the ITU which is the EU centre for the study of highly radioactive materials. Materials in a high-radiation environment (such as a reactor) can undergo unique behaviors such as swelling and non-thermal creep. If there are nuclear reactions within the material (such as what happens in the fuel), the stoichiometry will also change slowly over time. These behaviors can lead to new material properties, cracking, and fission gas release. The thermal conductivity of uranium dioxide

1700-566: Is formed into pellets and inserted into Zircaloy tubes that are bundled together. The Zircaloy tubes are about 1 centimetre (0.4 in) in diameter, and the fuel cladding gap is filled with helium gas to improve heat conduction 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 14×14 to 17×17. PWR fuel bundles are about 4 m (13 ft) long. In PWR fuel bundles, control rods are inserted through

1785-450: Is known about uranium carbide is in the form of pin-type fuel elements for liquid metal fast reactors during their intense study in the 1960s and 1970s. Recently there has been a revived interest in uranium carbide in the form of plate fuel and most notably, micro fuel particles (such as tristructural-isotropic particles). The high thermal conductivity and high melting point makes uranium carbide an attractive fuel. In addition, because of

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1870-413: Is low; it is affected by porosity and burn-up. The burn-up results in fission products being dissolved in the lattice (such as lanthanides ), the precipitation of fission products such as palladium , the formation of fission gas bubbles due to fission products such as xenon and krypton and radiation damage of the lattice. The low thermal conductivity can lead to overheating of the center part of

1955-921: Is not profitable, but does provide some cost relief. Disposal of submarines by the SRP costs the Navy US$ 25–50 million per submarine. Once the de-fueled reactor compartment is removed, it is sealed at both ends and shipped by barge and multiple-wheel high-capacity trailers to the Department of Energy 's Hanford Nuclear Reservation in Washington state , where they are currently, as of 2016, kept in open dry storage and slated to be eventually buried. Russian submarine reactor compartments are stored in similar fashion at Sayda-Guba (Sayda Bay) in northwestern Russia and Chazhma Bay near Vladivostok . The burial trenches have been evaluated to be secure for at least 600 years before

2040-593: Is official date used to secure FY2004 funding; work did not begin until 19 October. La Jolla (SSN-701) is currently undergoing conversion to a moored training ship at Norfolk Naval Shipyard. San Francisco (SSN-711) will be converted after decommissioning. Some of these submarines (the Lafayette class) were fleet ballistic missile boats for the vast majority of their careers. However, they were converted to SSNs for use as moored training platforms and are not currently scheduled for recycling. † A dagger after

2125-428: Is scheduled to operate as an MTS until 2014 while undergoing shipyard availabilities at four-year intervals. Nuclear fuel Nuclear fuel refers to any substance, typically fissile material, which is used by nuclear power stations or other nuclear devices to generate energy. For fission reactors, the fuel (typically based on uranium ) is usually based on the metal oxide ; the oxides are used rather than

2210-529: The C concentration will be too low for use in nuclear batteries without enrichment. Nuclear graphite discharged from reactors where it was used as a moderator presents the same issue. Liquid fuels contain dissolved nuclear fuel and have been shown to offer numerous operational advantages compared to traditional solid fuel approaches. Liquid-fuel reactors offer significant safety advantages due to their inherently stable "self-adjusting" reactor dynamics. This provides two major benefits: virtually eliminating

2295-523: The George Washington , Ethan Allen , Lafayette , James Madison , and Benjamin Franklin classes . All of these submarines were commissioned 1959–1967, as the goal was to create a credible, survivable sea-based deterrent as quickly as possible. These submarines were nicknamed "41 for Freedom" once the goal of 41 nuclear-powered ballistic missile submarines (SSBNs) was established in

2380-564: The Environmental Protection Agency and United States Coast Guard , requiring their removal. Since then, and to help reduce costs, the remaining submarine sections are recycled, returning reusable materials to production. In the process of submarine recycling, all hazardous and toxic wastes are identified and removed, and reusable equipment is removed and put into inventory. Scrap metals and all other materials are sold to private companies or reused. The overall process

2465-494: The Idaho National Laboratory (INL), located 42 miles (68 km) northwest of Idaho Falls, Idaho , where it is stored in special canisters. At PSNS, the SRP proper begins. The salvage workers cut the submarine into three or four pieces: the aft section, the reactor compartment, the missile compartment if one exists, and the forward section. Missile compartments are dismantled according to the provisions of

2550-489: The London Dumping Convention restricted ocean disposal of radioactive waste and in 1993, ocean disposal of radioactive waste was completely banned. The US Navy began a study on scrapping nuclear submarines; two years later shallow land burial of reactor compartments was selected as the most suitable option. In 1990, USS  Scamp was the first US nuclear-powered submarine to be scrapped . By

2635-537: The Puget Sound Naval Shipyard and Intermediate Maintenance Facility , the Navy is looking at other, commercial or private sector options for Enterprise in an effort to reduce both the cost of the work and the time taken to dismantle such a large vessel, as well as negating the difficulty of towing the hulk all the way from Newport News, where it is stored, to Puget Sound. Enterprise will be used as

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2720-590: The SSM-N-8 Regulus cruise missile . However, this was intended to act merely as a stop-gap, as the Regulus was limited both by its size – the greatest number of missiles capable of being taken to sea was five aboard USS  Halibut – range and speed, as well as the fact that the submarine was required to surface to launch a missile. The intention was that the main element of the US Navy's contribution to

2805-535: The Strategic Arms Reductions Treaty . Until 1991, the forward and aft sections of the submarines were rejoined and placed in floating storage. Various proposals for disposal of those hulls were considered, including sinking them at sea, but none proved economically practical. Some submarines built prior to the 1978 banning of polychlorinated biphenyl products (PCBs) had the chemicals on board, which are considered hazardous materials by

2890-570: The University of Massachusetts Lowell Radiation Laboratory . Sodium-bonded fuel consists of fuel that has liquid sodium in the gap between the fuel slug (or pellet) and the cladding. This fuel type is often used for sodium-cooled liquid metal fast reactors. It has been used in EBR-I, EBR-II, and the FFTF. The fuel slug may be metallic or ceramic. The sodium bonding is used to reduce the temperature of

2975-404: The liquid fluoride thorium reactor (LFTR), this fuel salt is also the coolant; in other designs, such as the stable salt reactor , the fuel salt is contained in fuel pins and the coolant is a separate, non-radioactive salt. There is a further category of molten salt-cooled reactors in which the fuel is not in molten salt form, but a molten salt is used for cooling. Molten salt fuels were used in

3060-482: The "41 for Freedom" submarines to be completed was USS  George Washington , which was commissioned on 30 December 1959. The final boat to enter service was USS  Will Rogers , which was commissioned on 1 April 1967. The 41 submarines were ultimately superseded in service by the Ohio class , the first of which was commissioned in 1981. USS  Kamehameha , operating as a SEAL platform in her later years,

3145-509: The 18 to 24 month fuel exposure period. Mixed oxide , or MOX fuel , is a blend of plutonium and natural or depleted uranium which behaves similarly (though not identically) to the enriched uranium feed for which most nuclear reactors were designed. MOX fuel is an alternative to low enriched uranium (LEU) fuel used in the light water reactors which predominate nuclear power generation. Some concern has been expressed that used MOX cores will introduce new disposal challenges, though MOX

3230-504: The 37-pin standard bundle. It has been designed specifically to increase fuel performance by utilizing two different pin diameters. Current CANDU designs do not need enriched uranium to achieve criticality (due to the lower neutron absorption in their heavy water moderator compared to light water), however, some newer concepts call for low enrichment to help reduce the size of the reactors. The Atucha nuclear power plant in Argentina,

3315-537: The LFTR known as the Molten Salt Reactor Experiment, as well as other liquid core reactor experiments. The liquid fuel for the molten salt reactor was a mixture of lithium, beryllium, thorium and uranium fluorides: LiF-BeF 2 -ThF 4 -UF 4 (72-16-12-0.4 mol%). It had a peak operating temperature of 705 °C in the experiment, but could have operated at much higher temperatures since

3400-479: The TRISO particle more structural integrity, followed by a dense outer layer of PyC. TRISO particles are then encapsulated into cylindrical or spherical graphite pellets. TRISO fuel particles are designed not to crack due to the stresses from processes (such as differential thermal expansion or fission gas pressure) at temperatures up to 1600 °C, and therefore can contain the fuel in the worst of accident scenarios in

3485-526: The US and an additional 35 in other countries. In a fast-neutron reactor , the minor actinides produced by neutron capture of uranium and plutonium can be used as fuel. Metal actinide fuel is typically an alloy of zirconium, uranium, plutonium, and minor actinides . It can be made inherently safe as thermal expansion of the metal alloy will increase neutron leakage. Molten plutonium, alloyed with other metals to lower its melting point and encapsulated in tantalum ,

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3570-856: The United Kingdom as part of the Dragon reactor project. The inclusion of the SiC as diffusion barrier was first suggested by D. T. Livey. The first nuclear reactor to use TRISO fuels was the Dragon reactor and the first powerplant was the THTR-300 . Currently, TRISO fuel compacts are being used in some experimental reactors, such as the HTR-10 in China and the high-temperature engineering test reactor in Japan. In

3655-519: The United States, spherical fuel elements utilizing a TRISO particle with a UO 2 and UC solid solution kernel are being used in the Xe-100 , and Kairos Power is developing a 140 MWE nuclear reactor that uses TRISO. In QUADRISO particles a burnable neutron poison ( europium oxide or erbium oxide or carbide ) layer surrounds the fuel kernel of ordinary TRISO particles to better manage

3740-401: The absence of oxygen in this fuel (during the course of irradiation, excess gas pressure can build from the formation of O 2 or other gases) as well as the ability to complement a ceramic coating (a ceramic-ceramic interface has structural and chemical advantages), uranium carbide could be the ideal fuel candidate for certain Generation IV reactors such as the gas-cooled fast reactor . While

3825-519: The aforementioned fuels can be made with plutonium and other actinides as part of a closed nuclear fuel cycle. Metal fuels have been used in light-water reactors and liquid metal fast breeder reactors , such as Experimental Breeder Reactor II . TRIGA fuel is used in TRIGA (Training, Research, Isotopes, General Atomics ) reactors. The TRIGA reactor uses UZrH fuel, which has a prompt negative fuel temperature coefficient of reactivity , meaning that as

3910-424: The application of the new fuel-cladding material systems for various types of ATF materials. The aim of the research is to develop nuclear fuels that can tolerate loss of active cooling for a considerably longer period than the existing fuel designs and prevent or delay the release of radionuclides during an accident. This research is focused on reconsidering the design of fuel pellets and cladding, as well as

3995-420: The boiling point of the molten salt was in excess of 1400 °C. The aqueous homogeneous reactors (AHRs) use a solution of uranyl sulfate or other uranium salt in water. Historically, AHRs have all been small research reactors, not large power reactors. The dual fluid reactor (DFR) has a variant DFR/m which works with eutectic liquid metal alloys, e.g. U-Cr or U-Fe. Uranium dioxide (UO 2 ) powder

4080-420: The chain-reaction. This mechanism compensates for the accumulation of undesirable neutron poisons which are an unavoidable part of the fission products, as well as normal fissile fuel "burn up" or depletion. In the generalized QUADRISO fuel concept the poison can eventually be mixed with the fuel kernel or the outer pyrocarbon. The QUADRISO concept was conceived at Argonne National Laboratory . RBMK reactor fuel

4165-510: The coolant and contaminating it. Besides the prevention of radioactive leaks this also serves to keep the coolant as non-corrosive as feasible and to prevent reactions between chemically aggressive fission products and the coolant. For example, the highly reactive alkali metal caesium which reacts strongly with water, producing hydrogen, and which is among the more common fission products. Pressurized water reactor (PWR) fuel consists of cylindrical rods put into bundles. A uranium oxide ceramic

4250-404: The early 1960s. The 1972 SALT I Treaty limited the number of American submarine-launched ballistic missile tubes to 656, based on the total missile tubes of the forty-one submarines, in line with the treaty's goal of limiting strategic nuclear weapons to the number already existing. The United States had deployed nuclear weapons aboard submarines for the purpose of deterrence since 1959, using

4335-539: The end of 2005, 195 nuclear submarines had been ordered or built in the US (including the NR-1 Deep Submergence Craft and Virginia , but none of the later Virginia class ). The last of the regular Sturgeon attack boats, L. Mendel Rivers , was decommissioned in 2001, and Parche , a highly modified Sturgeon , was decommissioned in 2004. The last of the initial " 41 for Freedom " fleet ballistic missile (FBM) submarines, Kamehameha ,

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4420-434: The established PUREX process is used commercially for about a third of all spent nuclear fuel (the rest being largely subject to a "once through fuel cycle"). All nitrogen-fluoride compounds are volatile or gaseous at room temperature and could be fractionally distilled from the other gaseous products (including recovered uranium hexafluoride ) to recover the initially used nitrogen. If the fuel could be processed in such

4505-496: The excess of reactivity. If the core is equipped both with TRISO and QUADRISO fuels, at beginning of life neutrons do not reach the fuel of the QUADRISO particles because they are stopped by the burnable poison. During reactor operation, neutron irradiation of the poison causes it to "burn up" or progressively transmute to non-poison isotopes, depleting this poison effect and leaving progressively more neutrons available for sustaining

4590-417: The existing Nimitz class ships, the US Navy was looking to extend the service life of Nimitz beyond 2026, and Dwight D. Eisenhower , which was planned to decommission in 2027. Hulls waiting or already processed by the recycling program are listed below. In September 2023, it was announced that, once any remaining radioactive and hazardous material had been removed, ex- Enterprise would be broken up at

4675-407: The fact that the used fuel can be cracked, it is very insoluble in water, and is able to retain the vast majority of the actinides and fission products within the uranium dioxide crystal lattice . The radiation hazard from spent nuclear fuel declines as its radioactive components decay, but remains high for many years. For example 10 years after removal from a reactor, the surface dose rate for

4760-412: The failure modes which occur during normal use (and the manner in which the fuel will behave during an accident) can be studied. In addition information is gained which enables the users of fuel to assure themselves of its quality and it also assists in the development of new fuels. After major accidents the core (or what is left of it) is normally subject to PIE to find out what happened. One site where PIE

4845-479: The first moored training ship achieved initial criticality. Modifications included special mooring arrangements including a mechanism to absorb power generated by the main propulsion shaft. Daniel Webster (SSBN-626) was converted to the second Moored Training Ship (MTS-2 / MTS-626) in 1993. The Moored Training Ship Site is located at Naval Weapons Station Charleston in Goose Creek, South Carolina . Sam Rayburn

4930-507: The first pinhole penetration of some lead containment areas of the reactor compartment packages occurs, and several thousand years before leakage becomes possible. In 1959 the US Navy removed a nuclear reactor from the submarine USS  Seawolf and replaced it with a new type. The removed reactor was scuttled in the Atlantic Ocean , 200 km (108 nmi) east of Delaware , at a depth of 2,700 m (8,858 ft). In 1972,

5015-403: The fuel being changed every three years or so, about half of the Pu is 'burned' in the reactor, providing about one third of the total energy. It behaves like U and its fission releases a similar amount of energy. The higher the burnup , the more plutonium is present in the spent fuel, but the available fissile plutonium is lower. Typically about one percent of the used fuel discharged from

5100-403: 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 reactor core. 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

5185-853: The fuel mixture for significantly extended periods, which increases fuel efficiency dramatically and incinerates the vast majority of its own waste as part of the normal operational characteristics. A downside to letting the Xe escape instead of allowing it to capture neutrons converting it to the basically stable and chemically inert Xe , is that it will quickly decay to the highly chemically reactive, long lived radioactive Cs , which behaves similar to other alkali metals and can be taken up by organisms in their metabolism. Molten salt fuels are mixtures of actinide salts (e.g. thorium/uranium fluoride/chloride) with other salts, used in liquid form above their typical melting points of several hundred degrees C. In some molten salt-fueled reactor designs, such as

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5270-408: The fuel of choice for reactor designs that NASA produces. One advantage is that uranium nitride has a better thermal conductivity than UO 2 . Uranium nitride has a very high melting point. This fuel has the disadvantage that unless N was used (in place of the more common N ), a large amount of C would be generated from the nitrogen by the (n,p) reaction . As the nitrogen needed for such

5355-406: The fuel rods, standing between the coolant and the nuclear fuel. It is made of a corrosion -resistant material with low absorption cross section for thermal neutrons , usually Zircaloy or steel in modern constructions, or magnesium with small amount of aluminium and other metals for the now-obsolete Magnox reactors . Cladding prevents radioactive fission fragments from escaping the fuel into

5440-540: The fuel. Accident tolerant fuels (ATF) are a series of new nuclear fuel concepts, researched in order to improve fuel performance under accident conditions, such as loss-of-coolant accident (LOCA) or reaction-initiated accidents (RIA). These concerns became more prominent after the Fukushima Daiichi nuclear disaster in Japan, in particular regarding light-water reactor (LWR) fuels performance under accident conditions. Neutronics analyses were performed for

5525-468: The interactions between the two. Used nuclear fuel is a complex mixture of the fission products , uranium , plutonium , and the transplutonium metals . In fuel which has been used at high temperature in power reactors it is common for the fuel to be heterogeneous ; often the fuel will contain nanoparticles of platinum group metals such as palladium . Also the fuel may well have cracked, swollen, and been heated close to its melting point. Despite

5610-473: The introduction of additional absorbers. CerMet fuel consists of ceramic fuel particles (usually uranium oxide) embedded in a metal matrix. It is hypothesized that this type of fuel is what is used in United States Navy reactors. This fuel has high heat transport characteristics and can withstand a large amount of expansion. Plate-type fuel has fallen out of favor over the years. Plate-type fuel

5695-437: The metals themselves because the oxide melting point is much higher than that of the metal and because it cannot burn, being already in the oxidized state. Uranium dioxide is a black semiconducting solid. It can be made by heating uranyl nitrate to form UO 2 . This is then converted by heating with hydrogen to form UO 2 . It can be made from enriched uranium hexafluoride by reacting with ammonia to form

5780-420: The neutron cross section of carbon is low, during years of burnup, the predominantly C will undergo neutron capture to produce stable C as well as radioactive C . Unlike the C produced by using uranium nitrate, the C will make up only a small isotopic impurity in the overall carbon content and thus make the entirety of the carbon content unsuitable for non-nuclear uses but

5865-612: The pellets during use. The porosity results in a decrease in both the thermal conductivity of the fuel and the swelling which occurs during use. According to the International Nuclear Safety Center the thermal conductivity of uranium dioxide can be predicted under different conditions by a series of equations. 41 for Freedom 41 for Freedom refers to the US Navy Fleet Ballistic Missile (FBM) submarines from

5950-570: The pilot project to look at the disposal of nuclear-powered aircraft carriers, with the lessons learned from the ship's eventual scrapping to be incorporated into the plans for the upcoming disposal of the first Nimitz -class ships. To this end, in 2024, the US Navy established the CVN Inactivation and Disposal Program Office, under the oversight of the Program Executive Office, Aircraft Carriers . In December 2020, it

6035-486: The possibility of a runaway reactor meltdown, and providing an automatic load-following capability which is well suited to electricity generation and high-temperature industrial heat applications. In some liquid core designs, the fuel can be drained rapidly into a passively safe dump-tank. This advantage was conclusively demonstrated repeatedly as part of a weekly shutdown procedure during the highly successful Molten-Salt Reactor Experiment from 1965 to 1969. A liquid core

6120-410: The reactor. Stainless steel was used in the past, but most reactors now use a zirconium alloy which, in addition to being highly corrosion-resistant, has low neutron absorption. The tubes containing the fuel pellets are sealed: these tubes are called fuel rods . The finished fuel rods are grouped into fuel assemblies that are used to build up the core of a power reactor. Cladding is the outer layer of

6205-496: The smallest and 800 assemblies for the largest BWR in the U.S. form the reactor core. Each BWR fuel rod is backfilled with helium to a pressure of about 3 standard atmospheres (300 kPa). Canada deuterium uranium fuel (CANDU) fuel bundles are about 0.5 metres (20 in) long and 10 centimetres (4 in) in diameter. They consist of sintered (UO 2 ) pellets in zirconium alloy tubes, welded to zirconium alloy end plates. Each bundle weighs roughly 20 kilograms (44 lb), and

6290-587: The steel pressure vessels, and the two reinforced concrete designs operated at 24.8 and 27 bars (24.5 and 26.6 atm). Magnox alloy consists mainly of magnesium with small amounts of aluminium and other metals—used in cladding unenriched uranium metal fuel with a non-oxidising covering to contain fission products. This material has the advantage of a low neutron capture cross-section, but has two major disadvantages: Magnox fuel incorporated cooling fins to provide maximum heat transfer despite low operating temperatures, making it expensive to produce. While

6375-503: The strategic nuclear deterrent be a ballistic missile armed submarine. The "41 for Freedom" nuclear-powered ballistic missile submarines (SSBNs) were armed with submarine-launched ballistic missiles (SLBMs) to create a deterrent force against the threat of nuclear war with any foreign power threatening the United States during the Cold War . The US Navy created a new submarine classification for these boats: SSBN. The first of

6460-560: The temperature of the core increases, the reactivity decreases—so it is highly unlikely for a meltdown to occur. Most cores that use this fuel are "high leakage" cores where the excess leaked neutrons can be utilized for research. That is, they can be used as a neutron source . TRIGA fuel was originally designed to use highly enriched uranium, however in 1978 the U.S. Department of Energy launched its Reduced Enrichment for Research Test Reactors program, which promoted reactor conversion to low-enriched uranium fuel. There are 35 TRIGA reactors in

6545-449: The top directly into the fuel bundle. The fuel bundles usually are enriched several percent in U. 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 Zircaloy 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 (BWR),

6630-407: The use of uranium metal rather than oxide made nuclear reprocessing more straightforward and therefore cheaper, the need to reprocess fuel a short time after removal from the reactor meant that the fission product hazard was severe. Expensive remote handling facilities were required to address this issue. Tristructural-isotropic (TRISO) fuel is a type of micro-particle fuel. A particle consists of

6715-424: The vast majority of their careers. However, they were briefly converted to SSNs before decommissioning and arrival at PSNS, and so are listed under that designation here. The nuclear-powered research submersible NR-1 is also included in this list. † A dagger after a completion date indicates that portions of the hull were preserved as memorials. See the individual articles for details. ‡ Date given for ex- Parche

6800-564: Was a U.S. proposal in the George W. Bush administration to form an international partnership to see spent nuclear fuel reprocessed in a way that renders the plutonium in it usable for nuclear fuel but not for nuclear weapons. Reprocessing of spent commercial-reactor nuclear fuel has not been permitted in the United States due to nonproliferation considerations . All other reprocessing nations have long had nuclear weapons from military-focused research reactor fuels except for Japan. Normally, with

6885-578: Was announced that a further nine Los Angeles -class attack submarines, two Ohio -class guided missile submarines, and the aircraft carrier Nimitz would be decommissioned and enter the recycling program by 2026. However, in November 2023, a further announcement was made that, owing to delays in both the construction of ships of the Gerald R. Ford class and the Refueling and Complex Overhaul work on

6970-516: Was decommissioned in 2002. Decommissioning of the Los Angeles boats began in 1995 with Baton Rouge . Additionally, a handful of nuclear-powered cruisers have entered the program, and their dismantling is ongoing. The first aircraft carrier due for decommissioning that would enter the SRP is planned to be Enterprise , which was withdrawn in 2013. Unlike the disposal of other nuclear powered surface ships, all of which have been recycled at

7055-528: Was decommissioned on 2 April 2002, the last boat of the original "41 for Freedom" submarines in commission, and the oldest submarine in the US Navy. Almost 37 years old, she held the record for the longest service lifetime of any nuclear-powered submarine. As of 2014, two boats, USS  Daniel Webster and USS  Sam Rayburn , though decommissioned, continue to serve as moored training ships , attached to Naval Nuclear Power School at Charleston , South Carolina . * Preserved as training vessels From

7140-400: Was tested in two experimental reactors, LAMPRE I and LAMPRE II, at Los Alamos National Laboratory in the 1960s. LAMPRE experienced three separate fuel failures during operation. Ceramic fuels other than oxides have the advantage of high heat conductivities and melting points, but they are more prone to swelling than oxide fuels and are not understood as well. Uranium nitride is often

7225-557: Was used in Soviet -designed and built RBMK -type reactors. This is a low-enriched uranium oxide fuel. The fuel elements in an RBMK are 3 m long each, and two of these sit back-to-back on each fuel channel, pressure tube. Reprocessed uranium from Russian VVER reactor spent fuel is used to fabricate RBMK fuel. Following the Chernobyl accident, the enrichment of fuel was changed from 2.0% to 2.4%, to compensate for control rod modifications and

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