GB918644A - Improvements relating to thermal nuclear reactors - Google Patents

Abstract

918,644. Moderator structures. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Nov. 21, 1961 [Nov. 30, 1960], No. 41154/60. Class 39 (4). A supporting framework for a solid moderator material comprises a grid with a layer of overlaid plates, the plates being positively located relative to the grid by sliding keying means directed radially from the plate centres and there being gaps between the plate edges so as to allow differential thermal expansion movements between the grid and the plates. As shown in Fig. 2, the keying means comprises two keys 14 with a reduced thickness joining piece between them welded to a grid bar 11 so as to project into keyways 15 machined in the undersides of adjacent plates. The keying means in this case are provided at the middle points of all four sides of each plate. Alternatively, the keying means may be provided at all four corners of each plate in which case, as shown in Fig. 4, upstanding keys 16 are grouped in a cruciform cluster of four and welded on an octagonal plate 17 let into the grid bars 11 to project into keyways 18 at the adjacent corners of four plates. Should differential thermal expansion movements occur between the grid and the plates, the latter will expand or contract individually relative to the grid, but by virtue of the keying this expansion or contraction is controlled so as to radiate from the plate centres; consequently the positions of these centres relative to the grid remain unchanged and large differentials at the periphery are obviated.