Patent ID: 6026138
Filing Date: 2000-02-15
Classification: G21C,Y02E

Abstract:
In a method for safeguarding the discharge of residual heat from a reactor of a nuclear power station in the case of a lowered filling level in a primary circuit of a reactor cooling system, the improvement which comprises:a) shutting down the reactor and running through an initial cooling and pressure reduction phase in the primary circuit of the cooling system;b) switching in an aftercooling system for taking over heat discharge from the primary circuit, in a state in which the heat discharge is no longer carried out by a steam generator plant;c) completing pressure relief and lowering of a filling level of the primary circuit to about a mid-loop level of a main coolant conduit;d) providing a coolant reservoir for a required refilling of at least one of the primary circuit of the reactor and the aftercooling system;e) connecting the coolant reservoir to a suction-side connecting conduit of the aftercooling system through an additional safety flood conduit provided with a shut-off valve and with a non-return valve controlled by a pilot valve;f) opening the shut-off valve during the lowering of the filling level according to step c);f.sub.1) passing coolant from the coolant reservoir into the suction conduit, by opening the non-return valve, as a function of geodetic head ratios and of a normal closing force of the non-return valve, when the filling level in the suction conduit falls below a predeterminable threshold value, in the case of a pressureless reactor cooling system; andf.sub.2) actuating the pilot valve to increase and thereby adapt the closing force of the non-return valve to modified pressure conditions in the evacuated reactor cooling system, when the reactor cooling system is evacuated for coolant degassing.