COUNTERCURRENT GAS-LIQUID FLOW IN A BOILING WATER REACTOR CORE DURING POSTULATED LOSS-OF-COOLANT ACCIDENTS

Countercurrent gas-liquid flow in parallel vertical channels is theoretically and experimentally evaluated for a boiling system simulating a BWR core. The parallel channel models are applied to the LOCA analysis program, SAFER, and verified by Two Bundle Loop test analysis. Applying the parallel channel effects to the fuel bundle, water drain tubes with the restricted bottom ends are developed in order to mitigate CCFL at the core outlet.