Valve control for low temperature overpressure protection in a nuclear power plant

摘要

A control system for overpressure protection of the reactor coolant boundary (14) in a nuclear power plant, comprising a pressure relief line (18a) having a power operated relief valve (24a) controlled by a circuit responsive to the condition of the reactor coolant and a control logic. The circuit includes a mode selector switch (80) having a NORMAL position (82) for establishing a full power overpressure relief valve setpoint (62) and a LTOP position (84) for establishing a low temperature overpressure relief setpoint (58). The control system logic opens the relief valve (24a) when (a) the mode switch is in the NORMAL position and the coolant pressure exceeds the full power setpoint (62), or (b) when the mode switch is in the LTOP position, the coolant temperature is less than a preselected value (52) and the coolant pressure exceeds the LTOP setpoint (58).