GB1121979A - An annular fuel element for a nuclear reactor - Google Patents

Abstract

1,121,979. Fuel elements. COMMISSARIAT A L'ENERGIE ATOMIQUE. 26 May, 1967 [27 May, 1966], No. 24502/67. Heading G6C. An annular fuel element for a natural uranium reactor cooled by circulation of CO 2 gas in the same direction inside and outside the element comprises a tubular slug of nuclear fuel covered with external and internal cladding, both of which have fins arranged in chevrons and are connected by annular plugs, the external cladding and plugs being made from a Mg-based alloy and the internal cladding from Zr or a Zr-based alloy having a higher hot strength than the Mg alloy. Suitable Zr alloys are Zircaloy ATR (containing, by wt., 0À5% Cu and 0À5% Mo), Zircaloy AJR (containing, by wt., 1% Cu and 1À5% Mo) and Zircaloy-2 (containing, by wt., 1À5% Sn and small additions of Ni, Cr and Fe). The fins on the internal cladding are preferably shallower than those on the external cladding. The external cladding may also have longitudinal partitions for centering the fuel element in a coolant duct. An annular disc of thermally insulating material resistant to creep when hot (e.g. a ceramic) is interposed between each plug and the fuel. The fuel is covered with the cladding members which are then forced against the fuel by any suitable method, e.g. hydraulic cladding after temporary plugging. The permanent plugs are then attached. The cladding members are preferably anchored on circular grooves in the fuel to prevent a ratchet effect during thermal cycling. The plugs are joined to the external cladding by arc-welding in an argon atmosphere or by electron beam welding and to the internal cladding by a process similar to that described in Specification 1,099,025.