GB985969A - Improvements relating to nuclear reactors - Google Patents

Abstract

985, 969. Moderator structures. ENGLISH ELECTRIC CO. Ltd. July 20, 1961 [July 20, 1960], No.25282/60. Heading G6C. A moderator core structure for a nuclear reactor comprises a plurality of layers of prismatic graphite blocks 30, 31 with longitudinally extending fuel channels 18 and arranged in a square lattice with transverse clearance spaces between adjacent blocks in each layer, wherein the blocks of at least some of the layers, e.g. blocks 30 of alternate layers, are provided with longitudinally extending locating faces 35 which are in overlapping sliding relationship with the corresponding faces of the transversely adjacent blocks so as to maintain the blocks in their correct position in the lattice without hindering either contraction or expansion of individual blocks transversely. In the embodiment shown in Fig. 2, each block 30 has on each face two diagonally opposed projections 34 which provide two oppositely directed, longitudinally spaced locating faces 35. Recesses 36 are provided in the blocks 31 so as to accommodate the projections 34 should relative vertical movement of adjacent columns occur. The end faces of each block 30, 31 are formed with castellations 32 having chamfered edges 33 which interlock when the columns are assembled so as to prevent relative rotation of the blocks and to maintain them in axial alignment. The castellations 32 on the blocks of the bottom layer engage locating pads secured to a support plate so as to prevent rotation of the blocks of this layer and hence of all other layers. As seen in Fig. 5, peripheral locating blocks 30<SP>1</SP>, 31<SP>1</SP> are disposed between circumferentially-extending locating rings, 40, 41 spaced by vertical webs 48. The rings 40, 41 are located with respect to eight vertical box beams 49 spaced around the core by means of radial key structures 50. Each structure 50 comprises a vertical web 52 and a pair of horizontal webs 53 secured to one of the beams 49, the vertical web 52 being engaged by pads 54 secured by screws 55 to the vertical webs 48. The rotation of groups of core blocks is prevented by the vertical webs 52 whilst a certain amount of lateral movement of the core is permitted by the sliding action of the pads 54 on the webs 52. Specification 963, 145 is referred to.