Method and device for preventing generation of thermal stress in lmfbr type reactors

Purpose: To provide the subject method and device wherein even when a part of the main cooling system is in trouble, the safe operation of the reactor can be continued by other sound main cooling system without generating thermal stress at the outlet nozzle and the like of the reactor container. Method: The lmfbr type reactor comprises a reactor container, a plurality of primary main cooling systems and each having a check valve and an intermediate heat exchanger, and an overflow tank controlling the liquid surface level of the coolant within the container. Between the hot leg and the tank of the primary main cooling system there is connected a branched piping having a flow adjusting valve and having a flow quantity greater than the counterflow leakage quantity of the check valve. In a case where the operation of the reactor is continued in a state where the operation of a part of the primary main cooling system is stopped, the coolants within the hot legs are caused to flow in the tank and thermal stresses generated in the container and the primary main cooling system are removed by the coolants leaking and counter flowing from the check valve. (Aizawa, K.)