Cooling structure for reactor container

Purpose: To eliminate thermal shocks to the incore structures and the reactor container walls at the upper end of a cold plenum. Constitution: Coolants in the high pressure plenum are distributed in the circumferential direction of the reactor container through distribution tubes or the like and entered into an uprising channel. The coolants, after cooling the reactor container walls, are introduced by way of a descending channel and a returning pipeway through the cold plenum and then to an exit of an intermediate heat exchanger or the suction port for the main recycling pump. In this way, the high temperature coolants, after cooling the reactor container walls, are mixed with coolants discharged from the intermediate heat exchanger or a low temperature coolants in the cold plenum sucked into the main recycling pump, so that the high temperature coolants stay does not stay in the upper end of the cold plenum. (Sekiya, K.)