Fuel elements, nuclear

SiHcon carbide s relatively low neutron cross section and good resistance to radiation damage make it useful in some of its new forms in nuclear reactors (qv). SiHcon carbide temperature-sensing devices and stmctural shapes fabricated from the new dense types are expected to have increased stabiHty. SiHcon carbide coatings (qv) may be appHed to nuclear fuel elements, especially those of pebble-bed reactors, or siHcon carbide may be incorporated as a matrix in these elements (153,154). 

B.R.T. Erost. Nuclear Fuel Elements. Pergamon Piess, Oxford (1982). 

SEALED SOURCE A soui ce Containing any radioactive substance whose structure is such as to prevent, under normal conditions of use, any dispersion of radioactive substances into the envu onment, but it does not include any radioactive substance inside a nuclear reactor or any nuclear fuel element. 

In 1976 the Swedish government stipulated that no new nuclear reactors should be charged until it had been shown how the radioactive waste products could be taken care of in an "absolutely safe manner" (8). Consequently, the nuclear power industry (through their joint Nuclear Fuel Supply Co, SKBF) embarked on a program referred to as the Nuclear Fuel Safety (KBS) Project (8). In one of the schemes (9) a repository for spent nuclear fuel elements in envisaged at a depth of 500 m in granitic bedrock. The repository will ultimately contain 6000 tonnes of uranium and 45 tonnes of plutonium. The spent fuel elements will be stored in copper cylinders (0.8 m in diameter and 4.7 m in length) with a wall thickness of 200 mm the void will be filled with lead. 

Rowe, D. S, 1970, COBRA II Digital Computer Program for Thermal Hydraulic Subchannel Analysis of Rod Bundle Nuclear Fuel Elements, BNWL 1229, Battelle Northwest Laboratory, Richland,... 

Nuclear and magneto-hydrodynamic electric power generation systems have been produced on a scale which could lead to industrial production, but to-date technical problems, mainly connected with corrosion of the containing materials, has hampered full-scale development. In the case of nuclear power, the proposed fast reactor, which uses fast neutron fission in a small nuclear fuel element, by comparison with fuel rods in thermal neutron reactors, requires a more rapid heat removal than is possible by water cooling, and a liquid sodium-potassium alloy has been used in the development of a near-industrial generator. The fuel container is a vanadium sheath with a niobium outer cladding, since this has a low fast neutron capture cross-section and a low rate of corrosion by the liquid metal coolant. The liquid metal coolant is transported from the fuel to the turbine generating the electric power in stainless steel... 

Purex [Plutonium and uranium recovery by extraction] A process for the solvent extraction of plutonium from solutions of uranium and fission products, obtained by dissolving spent nuclear fuel elements in nitric acid. The solvent is tri-n-butyl phosphate (TBP) in... 

Ball, C. I, Buykx, W. J. et al. 1989. Titanate ceramics for the stabilization of partially reprocessed nuclear fuel elements. Journal of the American Ceramic Society, 72, 404-414. 

Later studies by investigators (Alberts ei al 1979) have shown lhai 1 >7Cs introduced into a watershed is attached to soil panicles, which arc removed by erosion and runoff. Some of the eroded soil panicles comprise he sediments of the catchment basins in the watersheds and act as "sinks for, 7Cs. Other investigators have reponed an almost irreversible fixation of this clement in clay imerlattice sites in freshwater environments, and. that it is unlikely that this nuclide will he removed from these sediments under normal environmental conditions other than by exposure to solutions ol high ionic strength, such as may occur in estuarine environments. Studies of 15 Cs have been important because ihe element can be introduced into a water system from a leak in a nuclear fuel element. These findings are reported in some detail by Alberts ct al. in Science, 203. 649-651 (1979). 

Zirconium hydride, ZrH2, finds application as an antioxidant for rubber, in addition to being a moderator for nuclear fuel elements, and as a hydrogenation catalyst. Zirconium hydroxide, best formulated as Zr02 hH20 because of its variable water content, is used as a drying agent and absorbent and also has deodorant properties.19... 

Purex [Plutonium and uranium recovery by extraction] A process for the solvent extraction of plutonium from solutions of uranium and fission products, obtained by dissolving spent nuclear fuel elements in nitric acid. The solvent is tri- -butyl phosphate (TBP) in kerosene. First operated by the U.S. Atomic Energy Commission at its Savannah River plant, SC, in 1954 and at Hanford, WA, in 1956. Now in operation, with modifications, in several countries. Sites include Savannah River (SC), Cap de la Hague (France), Marcoule (France), Sellafield (England), Karlsruhe (Germany), and Trombay (India). See also Recuplex. 

In a repository of the type planned to be used in Sweden and Einland, the spent nuclear fuel elements will be placed in copper canisters with an iron insert. The canisters will be embedded in bentonite clay in the bedrock at a depth of about 500 m. In the event of a complete barrier failure, groundwater can enter the canister. At this depth groundwater (containing approximately 2 mM HCOg")... 

Suripto, A., Yuwono, I., Badruzzaman, M., Nasution, H., Kusnowo, A., and Amini, S.S., Proceedings of the Second Scientific Presentation on Nuclear Fuel Cycle Nuclear Fuel Element Development Centre, National Atomic Energy Agency, 1998 89-94. 

The performance requirements for ceramic nuclear fuel elements include the following dimensional stability to high fuel burnups, fission product retention, corrosion resistance, high thermal performance, fabricability, economic advantage, inspectability, and chemical reprocessing and recycling. 

Graphite is used as cladding for nuclear fuel elements because of its low neutron-absorption cross section and good moderating properties, as well as its high temperature properties and high heat capacity. 

The first attention given to actinide photochemistry was for the purpose of identifying any photochemical activity which might alter the efficiency of the extraction or exchange processes. Subsequently, the identification of photochemically active species of uranium and plutonium gave some indication that the photoreactions could be turned to a useful end and, perhaps, offer a cleaner way to separate actinides from each other and from the other elements accompanying them in nuclear fuel elements. 

Use Gas turbines rocketmotorparts turbojet engine components nuclear fuel elements coatings for high-temperature resistance sensing elements in instruments seals bearings, etc. in special pumps and other equipment. 

The array of nuclear fuel elements and moderator in a nuclear reactor. 

Use Cladding for nuclear fuel elements and other reactor applications. 

Many hydrometallurgical processes or process steps are used to upgrade concentrates, process recycled scrap metal, or purify aqueous process steams. Examples are (I) the leaching of molybdenite concentrate to remove Knpurities ,ft (2) leaching of tungsten carbide and molybdenum scrap-, (3) removal of copper impurities in nickel anolyte by cementation on metallic ruckel and (4) various methods for treating nuclear fuel elements. 

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