Depressurisation valve

A nuclear reactor having a pressurized cooling circuit comprising a depressurization valve, the depressurization valve comprising:

• an inlet;
• an outlet;
• a main valve configured to move between an open position and a closed position, the closed position preventing fluid flow through the main valve from the inlet to the outlet;
• a pilot line fluidically coupled to the inlet and closable by a first control valve, the first control valve controlled by pressure at the inlet to open above a low pressure threshold;
• a second control valve controlled by pressure at the inlet and configured to open above a high pressure threshold, the high pressure threshold being greater than the low pressure threshold;
• and
• a valve dome containing a first piston coupled to the main valve, the valve dome being fluidically coupled to the pilot line, wherein:
• in normal operation, the pilot line is operable to transmit fluid pressure from the inlet into the valve dome to apply pressure on a first face of the first piston, the first piston thereby applying a first force to the main valve urging it into the closed position, and
• when in operation the pressure in the pressurized cooling circuit is lower than the low pressure threshold, the first control valve is configured to close and remove the pressure from the first face of the first piston and allow the main valve to open,
• when in operation the pressure in the pressurized cooling circuit is higher than the high pressure threshold, the second control valve is configured to open and fluidically couple the valve dome to a bleed line, to reduce the pressure in the valve dome by releasing fluid from the valve dome through the bleed line, the bleed line having a lower fluid resistance than the pilot line when the second control valve is open.