稳压器卸压阀卸压效果研究

Study on Depressurization Efficiency of Pressurizer Relief Valves

基于国际上模拟严重事故瞬态过程最详细的机理性程序SCDAP/RELAP5/MOD3.1,主要分析研究了核电站未紧急停堆的预期瞬变(ATWS)初因(失去主给水、失去厂外电和控制棒失控提升)叠加辅助给水失效导致的堆芯熔化严重事故进程,并验证阻止ATWS导致堆芯熔化进程的一次侧卸压缓解措施的充分性和有效性。计算分析结果显示,一列稳压器卸压阀不足以充分降低一回路压力,压力仍然停留在10MPa以上,存在很大高压熔堆的风险。增加一列卸压阀可把一回路压力降低到3MPa左右,安注系统得以投入,及时有效地阻止堆芯熔化进程,降低了高压熔堆风险。分析结果还显示高压安注系统的投入对一回路卸压具有重要影响。

Based on SCDAP/RELAP5/MOD3.1,which may simulate the detail severe accident transient mechanism,this paper analyzes the progression and depressurization efficiency of postulated ATWS accident,initiated by the loss of main feed water(LOFW),the loss of off-site power(LOOP) and uncontrolled rod cluster control assembly(RCCA) bank withdrawal.The results show that one train of pressurizer relief valves(PRV) is not sufficient to depressurize reactor coolant system(RCS),and the primary pressure still remains above 10MPa;it brings a great potential risk of high-pressure core melt.The case adding one more train of PRV is analyzed and the results show that two trains of PRV could adequately reduce the primary pressure to about 3MPa,and the safety injection starts up and arrests the core melt progression,and thus reduce the risk of high-pressure core melt.It is also showed that the high pressure injection system has important contribu-tion to RCS depressurization.