GB1256701A - - Google Patents

Abstract

1,256,701. Reactors. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. 7 Feb., 1969 [7 Feb., 1968 (2); 25 March, 1968 (3); 29 April, 1968 (2)], Nos. 6167/68, 6168/68, 14343/68, 14344/68, 14345/68, 20264/68 and 20265/68. Heading G6C. In a gas-cooled fast reactor employing porous fuel in the form of coated fuel particles bonded together to form tubular fuel elements, the coolant gas flowing radially across the fuel between the inner and outer surfaces of the elements, means are provided to ensure that the gas pressure drop between the inner and outer surfaces is uniform along the length of the elements. One example of fuel element 1, Figs. 2, 3, which, in use, is mounted vertically in spaced relationship with other similar elements to form the reactor core, comprises a stack of annular cartridges 6a of porous fuel arranged between lower and upper end fittings 3, 5, respectively. The outer surfaces of the cartridges 6a are bounded by overlapping sleeves 7 of stainless steel mesh and the inner surfaces are bounded by overlapping tubes 8a of ceramic having gas ports 11 leading to annular grooves 10. The coolant gas enters the core through holes in the bottom grid 18 in which the fuel elements 1 are held by latches 17, the gas flowing through the spaces between the elements and entering the space 2 within the elements by flowing radially inwards through the fuel cartridges 6a, the heated gas leaving through the divergent passages 4 in the end fittings 5. The upper ends of the elements 1 are sealed by rings 20 in an upper grid (not shown). Graphite bushes 15, 19 serve as neutron reflectors. The gas pressure drop in the radial direction is made uniform along the length of the fuel element by gradually increasing the diameter of the space 2 in the direction from the upstream to the downstream end. In another embodiment, Fig. 5, the tubular fuel elements 31 are provided at their downstream ends 36 with conical baffles 38 which cause the coolant to take a longer path in passing through the porous fuel and thus cause an increase in gas pressure drop in this region. In another embodiment, Fig. 6, the coolant gas flows through the inlet spaces 43 between the tubular fuel elements 41 in a direction opposite to that in which it leaves through the spaces 44 in the fuel elements, whereby the gas pressure drop is kept uniform along the length of the elements. In a further embodiment, Fig. 7, the fuel elements 51a, 51b, are in the form of truncated hollow cones, the coolant gas entering through holes 55 and leaving through holes 58. The gas pressure drop is determined by the slope of the cones and also by the thickness of the cone walls which increases upwardly from the cone base.