Simulation of Phts Overpressure Protection Capability Under Severe Accident Conditions at Wolsong

Abstract

The over-pressure protection in a typical CANDU reactor is provided through two separate series of twin valves (liquid relief valves (LRVs) and liquid relief valves (DCRVs)), and is not a direct and unobstructed pathway for energy release from the main heat transport system. Therefore, under certain accident conditions when energy relief must become the sole or dominant heat sink, the steam and surge relief must occur through two series of valves (four LRVs and two DCRVs), separated by long piping and a degasser or bleed condenser tank. The upstream LRVs are larger, less resistive valves with typically double the flow capacity of that by the DCRVs, which is needed to increase their steam relief capacity in order to avoid limiting the discharge flow by themselves.