Analysis of a Typical BWR/4 MSIV Closure ATWS Using RAMONA-3B and TRAC-BD1 Codes

摘要

Analysis of a typical BWR/4 Anticipated Transient Without Scram (ATWS) has been performed using two advanced, best-estimate computer codes, namely, RAMONA-3B and TRAC-BD1. The transient was initiated by an inadvertant closure of all Main Steam Isolation Valves (MSIVs) with subsequent failure to scram the reactor. However, all other safety features namely, the safety and relief valves, recirculation pump trip, high pressure coolant injection and the standby liquid (boron) control system were assumed to work as designed. No other operator action was assumed. It has been found that both RAMONA-3B (with three-dimensional neutron kinetics) and TRAC-BD1 (with point kinetics) yielded similar results for the global parameters such as reactor power, system pressure and the suppression pool temperature. Both calculations showed that the reactor can be brought to hot shutdown in approximately twenty to twenty-five minutes with borated water mass flow rate of 2.78 kg/s (43 gpm) with 23800 ppM of boron. The suppression pool water temperature (assuming no pool cooling) at this time could be in the range of 170 to 205 exp 0 F. An additional TRAC-BD1 calculation with RAMONA-3B reactor power indicates that the thermal-hydraulic models in RAMONA-3B, although simpler than those in TRAC-BD1, can adequately represent the system behavior during the ATWS-type transient. (ERA citation 09:037662)