nuclear reactor core with prismatic blocks of nuclear reactor core with the moderator and

摘要

1397463 Moderator structures UNITED KINGDOM ATOMIC ENERGY AUTHORITY 2 May 1973 [19 June 1972] 28684/72 Heading G6C A prismatic block 1 of moderator material, e.g. graphite, for use with similar blocks in forming a core for a high temperature gascooled reactor, has end faces shaped as irregular hexagons with three long sides a of equal length and three short sides b also of equal length, one short side being disposed between each pair of adjacent long sides, which long sides are inclined at 60 degrees to one another, the block 1 defining a plurality of coolant channels 7 disposed parrallel to the sides of the block. Nuclear fuel in the form of fuel pins or fuel compacts (not shown) is disposed in at least some of the channels 7. Alternatively, the fuel may be disposed in bores formed between adjacent channels 7. The reactor core comprises a plurality of vertical columns composed of prismatic blocks 1 arranged in groups of six each surrounding a smaller moderator block 2 which is hexagonal in plan and is pierced by a single axial hole 3 for receiving a reactor control rod. Protuberances 5 on the flanks of the blocks 2 engage in recesses 6 in the shorter sides of the six blocks 1 which surround it. A central hole 8 is provided in each block 1 for engagement by a remote handling tool . Closable refuelling standpipes 9 are positioned coaxial over one third of the control rod columns formed by the blocks 2. These standpipes are disposed on a triangular lattice and when projected on to the core, overlap a part of each of the six blocks 1 contiguous with the adjacent control rod column. Through each standpipe 9 the underlying control rod blocks 2 can be lifted to be replaced, and the blocks 1 from any one of six columns can also be replaced by means of a rigid cranked shaft carrying a grapple adapted to engage in a hole 8. The control rod columns which do not coincide with refuelling standpipes 9 lie beneath further, smaller diameter standpipes 10.