GB1330031A - High temperature gas cooled reactor fuel elements - Google Patents

Abstract

1330031 Fuel elements UNITED KING- DOM ATOMIC ENERGY AUTHORITY 17 March 1972 [22 March 1971] 7507/71 Heading G6C A nuclear reactor fuel element, particularly for a high temperature gas-cooled reactor, comprises a tubular member composed of a stack of nuclear fuel-containing annular discs 2 with provision for coolant to flow between adjacent discs. The discs 2 each have a central hole of uniform bore while their outer diameters gradually increase from the lower end to the upper end of the stack. The discs 2 are centred on a porous ceramic or wire mesh sleeve 3, and the resultant stack is enclosed peripherally by a similar but gradually tapered outer sleeve 4. Each disc 2 is composed of a double layer of coated fissile fuel particles 2a embedded in a graphite matrix, and moulded in graphite on the underside of each disc are three radial ribs 5 which act as spacers. These ribs 5 coincide with three unfuelled radial zones in the adjacent discs 2 of the stack. Coolant gas flows from a pressure gas supply plenum 7 to an outlet plenum 8, passing in turn through the outer sleeve 4, the coolant spaces between adjacent discs 2, the inner sleeve 3, and the centre bore of the stack. The upper and lower regions A and B are occupied by unfuelled graphite to act as a reflector for operation in a thermal reactor, or by fertile material for operation in a fast reactor. In either use, the material in these regions may be formed as ribbed discs so as to be cooled in a similar manner to the fissile fuel. Alternative matrix materials are silicon carbide and pyrocarbon. Where the discs may be subjected to such thermal gradients as will set up unaccept- ably high thermal stresses, radial gaps are formed in the discs to prevent their fracture. In a modified form, part conical annular discs are employed instead of flat annular discs. In either case, the coolant flow direction may be the reverse of that described above.