严重事故下小型安全壳内氢气风险分析

Analysis of Hydrogen Risk in Containment under Severe Accident

采用三维计算流体力学分析程序GASFLOW对小堆大破口冷却剂丧失事故(LBLOCA)叠加应急堆芯冷却系统失效导致的严重事故期间安全壳内的氢气风险进行分析。结果表明,当发生LBLOCA时,大量的高温高压水/蒸汽喷入小型安全壳引起安全壳压力快速上升,迅速充满蒸汽,并将安全壳内的大部分空气迅速排出,形成蒸汽惰化;在对流较弱区域(如角落),存在氢气积聚现象;当事故进程发展到大量氢气产生时,由于安全壳内空气已经被蒸汽排出并惰化,虽然氢气浓度可以达到较高水平,但是混合气体处于可燃极限外,不存在氢气燃爆的风险。

In this paper,a three dimension computational fluid dynamics analysis program,GASFLOW,is applied to analyze the hydrogen risk in the containment in the severe accident caused by the large break loss of coolant accident(LBLOCA)combined with the failure of the emergency core cooling system(ECCS).The results show that a large amount of high temperature and pressure water/vapor is injected into the containment,which rapidly increases the pressure of the containment.In the weak convective regions,such as the corners,the phenomenon of hydrogen accumulation exists.After the accident evolves to the stage that a large amount of hydrogen is produced,the mixture is beyond the flammability limit because the air has been removed by the steam and formed an inert environment,although the hydrogen concentration could reach a high level.Consequently,there is no risk of hydrogen combustion or explosion in the LBLOCA sequence.