PURPOSE:To plan the reduction of thermal stress by forming a circular space between the inner circumference of a reactor vessel and a cylindrical partition wall, starting an electromagnetic pump and flowing the coolant in a cold pool into the circular space through a flowing opening. CONSTITUTION:A reactor core 11 is submerged in coolant 10, and an intermediate heat exchanger 13 and a coolant circulating pump 14 are arranged while the coolant 10 is stored in a reactor vessel 1. Further, the circumferential end of a partition wall 16 provided in the vessel 1 is jointed liquidtight with the inner circumference of a cylindrical partition wall 17, the inner part of the vessel 1 is divided into an upper hot pool 18A and a lower cold pool 18B by the wall 16, and an communicating opening 19 is provided in the lower end of the wall 17. An electromagnetic pump 24 is started, the coolant 10 in the pool 18B is flowed in a circular space 22 through the opening 19 to ascend in the space 22, and absorbed by the pump 24. Therefore, thermal stress produced in the vessel can surely be reduced.
展开▼
