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On the effect of accident conditions on the molten core debris relocation into lower head of a PWR vessel.

机译：事故条件对熔融岩心碎屑迁移至压水堆容器下部的影响。

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摘要

From 1975 to present, it has been found that the primary risk to the public health and safety from nuclear power reactors lies in "beyond design basis" accidents. During such severe accidents, melting of the reactor core may lead to a loss of primary system integrity, or even containment failure, which will allow escape of significant amounts of radioactive material to the environment. It is very important to understand the mechanism of reactor core degradation during a severe accident.; In this study, the damage progression of the reactor core and the slumping mechanism of molten material to the lower head of the reactor vessel were examined through simulation of severe accident scenarios that lead to large-scale core damage. The calculations were carried out using the computer code SCDAP/RELAP5.; Different modeling parameters or models were used in calculations by version MOD3.2. The cladding oxidation shell "durability" parameter, which can control the timing of fuel clad failure, was varied. The heat flux model of steady-state natural convection of the molten pool was changed. The ultimate strength of the crust supporting the molten pool was doubled. These changes were made to examine the effects on the calculated core damage, and the molten pool expansion and its slumping.; Different accident scenarios were simulated. The HPI/makeup flow rates were changed. The timing of opening and closing the PORV was considered. Reflood by restart of coolant pump 2B was also studied. Finally, the size of the PORV opening was also changed. The effects of these accident scenarios on accident progression and core damage process were studied.; From the calculated results, it was concluded that the accurate modeling of core damage phenomena was very important to the prediction of the later stage of an accident. According to code MOD3.2, the molten material in a pool slumped to the lower head of the reactor vessel when the juncture of the top and side crusts failed after the molten pool had reached the periphery of the core. The changes of reactor coolant system pressure contributed to the crust failure.
机译：从1975年至今，已经发现核动力反应堆对公众健康和安全的主要风险在于“超出设计基准”事故。在此类严重事故中，反应堆堆芯的熔化可能导致一次系统完整性丧失，甚至导致安全壳失效，这将使大量放射性物质逃逸到环境中。了解严重事故期间反应堆堆芯退化的机理非常重要。在这项研究中，通过模拟导致大规模堆芯损坏的严重事故场景，研究了反应堆芯的损坏进程和熔融材料向反应堆容器下端的塌落机理。使用计算机代码SCDAP / RELAP5进行计算。 MOD3.2版本在计算中使用了不同的建模参数或模型。可以控制燃料包层失效时间的包层氧化壳的“耐久性”参数是变化的。改变了熔池稳态自然对流的热通量模型。支撑熔池的地壳的极限强度增加了一倍。进行这些更改是为了检查对计算出的岩心损伤，熔池膨胀及其塌落的影响。模拟了不同的事故场景。 HPI /补充流速已更改。考虑了打开和关闭PORV的时间。还研究了由冷却剂泵2B重新启动引起的回油。最后，PORV开口的尺寸也发生了变化。研究了这些事故情景对事故进展和核心破坏过程的影响。从计算结果可以得出结论，核心损坏现象的准确建模对于预测事故的后期非常重要。根据代码MOD3.2，当熔池到达堆芯外围后，顶部和侧面结壳的接合处破裂时，熔池中的熔融材料会塌落到反应堆容器的下端。反应堆冷却剂系统压力的变化导致结壳故障。

著录项

  • 作者

    An, Xuegao.;

  • 作者单位

    University of California, Los Angeles.;

  • 授予单位 University of California, Los Angeles.;
  • 学科 Engineering Nuclear.; Chemistry Nuclear.; Physics Nuclear.
  • 学位 Ph.D.
  • 年度 1999
  • 页码 160 p.
  • 总页数 160
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 原子能技术;无机化学;原子核物理学、高能物理学;
  • 关键词

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