The Pressure Vessel Cooling Water (PVCW) system at Hinkley Point B is a critical safety function of the nuclear plant. It removes heat from the concrete reactor pressure vessel via a number of primary and backup cooling water pumps, all driven by 100HP electric motors.
The site licence holder at the time, British Energy, required an alternate – and also diverse – arrangement to keep the cooling pumps running in the event of electrical power loss. Diesel backup motors were ruled out as an option, due to the operational location of the pumps.
Denley Hydraulics devised a solution to provide power to the pumps via hydraulic motors mounted next to each pump, connected with a high-power toothed belt. The hydraulic motors were driven by a 125kW diesel power unit, located in a safe area over 100 metres away.
The hydraulic power units were fitted with an auto-start controller linked to pressure sensors in the cooling circuit. On detection of a fault in the electrically-powered pumps, the diesel engine starts automatically, driving the hydraulic motors and keeping the coolant pumps running.