【摘要】 现有概率安全评价指出，常规轻水堆的堆芯熔化频率及安全壳失效，放射性大量释放的频率都是很低的。但这些风险对于下一代先进轻水堆来说是不能忽略的。近年来西方对下一代先进轻水堆的安全目标作了更高的要求，即在严重事故的条件下，仍然能保证安全壳的完整性，而无需采取应急措施。这就要求对严重事故现象有足够的认识，以便对严重事故设置相应的缓解措施。本文简述了严重事故的物理现象、机理及可能的缓解策略，综述了这方面的研究进展。更多还原

【Abstract】 The available probabilistic safety analysis study shows that both the occurrence of core meltdown and the frequency of occurrence of outer containment failure are low.However,such risk can not be neglected for next generation advanced light water reactor.In recent years the high level safety objective,that is in case of severe accident there will be no need of off site emergency actions is presented.Thus the mechanical phenomena related to severe accident should be better understood so as to settle the possible mitigation solutions.This paper is to provide such synthesis in this filed.更多还原