In a nuclear reactor, pressure is maintained in the primary circuit by heating water with resistors or by spraying water inside the pressuriser which is connected to the primary circuit.
The Rolls-Royce Pressuriser Heater Controller includes the variable heating unit that adapts its heating power when pressure in the pressuriser differs from the pressure set-point. The variable heating unit is powered by two identical regulation cabinets (heating selectors) on each unit. The heating selectors increase and decrease the applied power if the pressure drops or rises. They are activated by the powering-up time control for the resistors or heaters.