堆芯晚期注水对一回路压力的影响分析

Analysis of Effect of Late Water Injection on RCS Repressurization

分析典型的1000 MW级压水堆核电厂在高压严重事故序列下,堆芯晚期注水对压力容器失效时一回路压力的影响。分析结果表明,在开启1列稳压器卸压阀的情况下,稳压器波动管可能会在压力容器失效之前发生蠕变失效使一回路被动卸压,堆芯晚期注水不会造成一回路压力大幅增大,但波动管失效的时间和尺寸存在较大的不确定性。在开启2列或3列卸压阀的情况下不会发生一回路被动卸压,堆芯晚期注水会增大压力容器失效时一回路的压力,增大熔融物高压喷射的风险;开启3列卸压阀可以将一回路的压力降到较低水平。投入2列安全注入的情况下,压力容器失效时一回路压力比投入1列安全注入的情况略高,但压力容器的失效时间被明显推迟。为了保证充足的衰变热移出能力、减小一回路卸压的不确定性、减小熔融物高压喷射的风险及延缓压力容器失效,较佳的做法是同时开启3列卸压阀并投入2列安全注入。

Effect of late water injection on RCS repressurization during high pressure severe accident sequence in a typical PWR was analyzed.As the results shown,late water injection could increase RCS pres-sure when RPV failed without RCS passive depressurization.Especially in the condition of opening one PORV,RCS pressure could reach high pressure limit when RPV failed and the risk of HPME and DCH was dramatically increased.Integrity of containment could be threatened.However,in the condition of RCS pas-sive depressurization induced by pressurizer surge line creep failure,RCS pressure could be decreased to very low level even only one PORV was opened and two trains of emergency core cooling were implemented.The risk of HPME and DCH was eliminated.The more PORVs were opened,the faster accident progression was and the earlier RPV failed.RCS pressure was a little higher when PRV failed if two trains of emergency core cooling was implemented comparing with the condition with only one train of emergency core cooling.However the time of RPV failure was obviously delayed.From the point of delaying RPV failure and pre-venting containment early failure of view,the optimized late water injection was opening threc PORVs and implementing two trains of emergency core cooling.