严重事故下蠕变诱发RCS破裂的概率评估

Probabilistic Assessment of Creep Induced RCS Rupture in Severe Accident

严重事故下一回路管道可能会发生蠕变失效,若出现蠕变诱发的蒸汽发生器传热管破裂(SGTR),则会导致安全壳旁路失效;若出现蠕变诱发热段或波动管的失效,则产生的破口将会使一回路迅速卸压。因此,评估严重事故下蠕变诱发反应堆冷却剂系统(RCS)破裂的可能性是开展严重事故分析、特别是二级概率安全分析(PSA)的重要基础。本工作基于蠕变失效模型,考虑传热管的缺陷,建立了评价蠕变诱发RCS破裂的确定论模型。在此基础上,运用拉丁超立方体抽样方法,考虑重要参数的不确定性,开发了严重事故下蠕变诱发RCS破裂的概率评估程序。随后对典型的事故序列进行了蠕变诱发RCS破裂的概率评估。结果表明,对于高压事故序列,存在一定的蠕变诱发SGTR概率,也存在较高的蠕变诱发热段或波动管失效概率。

The creep induced rupture of the reactor coolant system（RCS）may arise in severe accident,which may bypass the containment for creep induced steam generator tube rupture（SGTR）or depressurize the RCS quickly for creep induced hot leg or surge line break.Therefore,it is essential for severe accident analysis and especially for level2 probabilistic safety analysis（PSA）to evaluate the probability of creep induced RCS rupture in severe accident.In this paper,the deterministic model for creep induced RCS rupture was constructed based on creep rupture model,considering steam generator tube flaws.On the basis of the deterministic model,the probabilistic program was developed to evaluate creep induced RCS rupture in severe accident using Latin hypercube samplingmethod to consider the uncertainties for important parameters.Then the probabilities of creep induced RCS rupture for representative accident sequences were assessed.It is concluded that there are certain probabilities for creep induced SGTR and high probabilities for creep induced hot leg or surge line failures for high pressure accident sequences.