Cooling structure for the lower surface of reactor core support plate

In a HTGR type reactor in which the lower surface of a reactor support plate is cooled by supplying coolants between the reactor core support plate and a cover plate, gap between the reactor support plate and the cover plate is partitioned horizontally. In this case, a rectification plate having a gap is disposed at the periphery of a main coolant pipe which passes through the reactor core support plate and no gap at the periphery of an auxiliary coolant pipe which passes through the reactor core support plate is disposed. By such a constitution, since the coolants do not flow to the lower surface of the reactor core support plate from periphery of the auxiliary coolant pipe but all of them are flow to the lower surface of the reactor support plate from the periphery of the main coolant pipe radially and uniformly, the entire reactor core support plate can be cooled uniformly. (T.M.)