全厂断电引发的严重事故下蒸汽发生器传热管蠕变失效风险研究

全厂断电引发的严重事故若处置不当，可能发展为长期、高压的严重事故进程，此时堆芯冷却系统中的自然循环在导出部分堆芯余热的同时，也增加了蒸汽发生器（SG）传热管、稳压器波动管以及热管段出现蠕变失效的风险。本文基于两环路设计的秦山二期核电厂设计特点，结合蠕变失效风险模型，对全厂断电引发的严重事故后未能执行“严重事故管理导则中向蒸汽发生器注水（SAG-1）”时SG传热管的蠕变失效风险进行了研究，从而为全厂断电引发的严重事故的负面影响提供量化结果，为技术支持中心（TSC）最终决策提供参考依据。分析结果表明，全厂断电引发的严重事故后16 361 s可能出现蠕变失效；自事故后16 610 s，SG传热管出现蠕变失效的可能性均远低于稳压器波动管与热管段，秦山二期核电厂全厂断电引发的严重事故下因SG传热管蠕变失效而导致安全壳旁通的风险很小。

Risk Analysis for Steam Generator Tube Creep Rupture-Under Severe Accident Induced by Station Blackout

The severe accident induced by station blackout (SBO) could lead to a long-term and high pressure sequence with inappropriate mitigation and the risk of creep rupture of steam generator (SG) tubes, pressurizer surge line and hotleg would be significant due to natural circulation inside reactor coolant system. Based on the two-loop design of Qinshan Ⅱ NPP, together with a probabilistic creep rupture model, this paper performed detailed evaluation for risk of creep rupture of SG tubes without implementing the action of injection water into SG in severe accident management guide (SAMG) (SAG-1) following severe accident induced by SBO. Therefore, quantitative results of negative impact of severe accident induced by SBO are supported to TSC which is in charge of making the final decision for reference. It is concluded that the risk of creep rupture rises around 16 361 s since SBO. The risk of SG tube creep rupture is much lower than that of pressurizer surge line and hotleg after 16 610 s since SBO. The probability of containment bypass due to SG tube creep rupture is negligible during the severe accident induced by SBO for Qinshan Ⅱ NPP.