QUASI-STATIC CORE LIQUID-LEVEL DEPRESSION AND LONG-TERM CORE UNCOVERYDURING A PWR LOCA

The possibility exists that the core liquid level can be depressed qua si-statically during long-term plant cooldown following a cold-leg-bre ak loss-of-coolant accident in a pressurized-water reactor. Such a lev el depression can take place if the core steaming rate is almost balan ced with the steam condensation rate in the reactor coolant system (RC S). Integral experiments simulating three steam condensation modes in the RCS have shown that quasi-static level depressions can happen and thus have the potential for causing a prolonged uncovery and heatup of the core upper regions.