Reactor fuel element

Results of uranium weight determination in nuclear reactor fuel elements. 

Carbide-based cermets have particles of carbides of tungsten, chromium, and titanium. Tungsten carbide in a cobalt matrix is used in machine parts requiring very high hardness such as wire-drawing dies, valves, etc. Chromium carbide in a cobalt matrix has high corrosion and abrasion resistance it also has a coefficient of thermal expansion close to that of steel, so is well-suited for use in valves. Titanium carbide in either a nickel or a cobalt matrix is often used in high-temperature applications such as turbine parts. Cermets are also used as nuclear reactor fuel elements and control rods. Fuel elements can be uranium oxide particles in stainless steel ceramic, whereas boron carbide in stainless steel is used for control rods. 

Except for large scale accidental releases (e.g. nuclear explosions or catastrophic accidents at nuclear plants), water will be the main transport medium of plutonium to man. Therefore the size and location of plutonium sources, its pathways to man and its behaviour in natural waters are essential knowledge required for the evaluation of its ecological impact. That information, combined with radiological health standards, allows an assessment of the overall risk to the public from plutonium e.g. from a waste repository for spent unreprocessed reactor fuel elements in deep granite bedrock (8, 9). ... 

Development efforts in the nuclear industry are focusing on the fuel cycle (Figure 6.12). The front end of the cycle includes mining, milling, and conversion of ore to uranium hexafluoride enrichment of the uranium-235 isotope conversion of the enriched product to uranium oxides and fabrication into reactor fuel elements. Because there is at present a moratorium on reprocessing spent fuel, the back end of the cycle consists only of management and disposal of spent fuel. 

The maximum heat flux achievable with nucleate boiling is known as the critical heat flux. In a system where the surface temperature is not self-limiting, such as a nuclear reactor fuel element, operation above the critical flux will result in a rapid increase in the surface temperature, and in the extreme situation the surface will melt. This phenomenon is known as burn-out . The heating media used for process plant are normally self-limiting for example, with steam the surface temperature can never exceed the saturation temperature. Care must be taken in the design of electrically heated vaporisers to ensure that the critical flux can never be exceeded. 

Kjellstrom, B., and A. E. Larson, 1967, Improvement of Reactor Fuel Element Heat Transfer by Surface Roughness, Rep. AE-R-271, A B Atomenergi, Nykoting, Sweden. (5)... 

C. D. Hylton, R. E. Leuze, W. H. Lewis and W. R. Whitson ORNL Metal Recovery Plant Processing Clementine Reactor Fuel Elements. Terminal Report. Report ORNL-1941 (7. Sept. 1955) [Deklassifiziert mit Loschungen als ORNL-1941 (Del.)]. 

Hcit, W., Huschka, H, Rind, W., and Kaiser, G.G., Status of qualification of high-temperature reactor fuel element spheres, Nuclear Technology, 1985, 69, 44 54. 

Robertson, J.A.L. "Introductory Survey on Swelling and Gas Release" Physical Metallurgy of Reactor Fuel Elements Metals Society, London, 1975... 

D. R. Odander, Fundamental Aspects of Nuclear Reactor Fuel Elements, National Technical Information Service, Springfield, Va., 1976, Chapt. 17. 

Reactor fuel elements are contained in cans. In early British reactors, these were made of aluminium or aluminium/magnesium alloy to minimise capture of neutrons in the canning material. Nowadays, uranium fuel is enriched with respect to the 235U content, and the extra reactivity enables steel or zirconium cans to be used. In the original... 

Accumulated activities of actinoids and fissions products in the cores as well as the mean activity in individual reactor fuel elements of stands 27A T (the first and the second lifetimes) and KM-1 have been estimated as of the turn of 2003 and 2010. 

Fabrication of Water Reactor Fuel Elements, Proc. Symp., Prague, Nov. 6-10,1978 International Atomic Energy Agency, Vienna, 1979. 

R. Farmakes, ed.. Fast Reactor Fuel Element Technology, Proc. Int. Conf, April 13-15, 1971, New Orleans American Nuclear Society, La Grange, IL, 1971. 

Irradiation. Samples were irradiated in the Argonne high level gamma irradiation facility. y-Rays, from spent reactor fuel elements, ranged in energy from 0.22 to 2.5 Mev., with an average of about 0.75 Mev. The dose rates for various samples varied from 1 X 104 to 4 X 104 rads per minute. The temperature of the samples was about 30 °C. 

Enriched UF is shipped to the plant for fabricating reactor fuel elements in monel cylinders whose size is determined from the content, so as to prevent accumulation of a critical mass. At the fuel fabrication plant UF is converted to UO or other chemical form used in reactor fuel. For light-water reactors the UOj is pressed into pellets, which are sintered, ground to size, and loaded into zircaloy tubing, which is filled with helium and closed with welded zircaloy end plugs. These individual fuel rods are assembled into bundles, constituting the fuel elements shipped to the reactor. Conversion of UFj to UO2 is described in Chap. 5. Extraction of zirconium from its ores and separation of zirconium from its companion element hafnium is described in Chap. 7. 

The work required to enrich uranium in increases rapidly with the content of the product. Because of varying domestic prices on natural uranium, as well as varying content of in uranium obtained from used reactor fuel elements, so-called toll enrichment has been introduced. In this case, the purchaser himself provides the uranium feed into the separation plant and pays for the separative work required to make his desired product out of the uranium feed provided. Separative work is defined as... 

The absorption of radiation leads to an increase in die tenqierature of the absorber. An exanqile of this is the absorption of the kinetic energy of fission products in nuclear reactor fuel elements which is a main source of the heat production in reactors. The absorption of decay energy of radioactive nuclides in appropriate absorbing material can be used in a similar - albeit more modest - way as an energy source. 

The reprocessing of used reactor fuel elements involves solvent extraction processes with organic solvents. In these processes the solvents are subjected to high radiation fields with subsequent decomposition of the organic solvent. The design of chemical reprocessing systems must take into account any interference by the radiolytic products (Ch. 20). 

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