Suppression of malfunction under water-solid conditions

摘要

Malfunction under water-solid conditions responsive either to increase in mass flow or increase in heat flow into the reactor coolant is suppressed. The power-actuable reactor-coolant relief valve is opened for increase in reactor-coolant mass influx if the rate of change of coolant pressure exceeds a setpoint during a predetermined interval, if, during this interval, the coolant temperature is less than a setpoint and if the level of the fluid in the pressurizer is above a predetermined setpoint (water-solid state). The interval is set to preclude opening of the relief valve for transients. The relief valve is opened responsive to increased influx of heat to the reactor coolant only while the coolant pump operates for a predetermined interval after it starts, if the level of the fluid in the pressurizer is above a setpoint, if either the difference between the temperature of the secondary fluid in the steam generator and the temperature of the coolant is above a predetermined setpoint or the difference between the temperature of the coolant and of the coolant in the loop seal is greater than a predetermined setpoint and if the coolant temperature is less than the setpoint.