Abstract Although there are still controversial opinions and uncertainty on application of SiCf/SiC composite cladding as next-generation cladding material for its great oxidation resistance in high temperature steam environment and other outstanding advantages, it cannot deny that SiCf/SiC cladding is a potential accident tolerant fuel (ATF) cladding with high research priority and still in the engineering design stage for now. However, considering its disadvantages, such as low irradiated thermal conductivity, ductility that barely not exist, further evaluations of its in-pile behaviors are still necessary. Based on the self-developed code we recently updated, relevant thermohydraulic and mechanical models in FROBA-ATF were applied to simulate the cladding behaviors under normal and accident conditions in this paper. Even through steady-state performance analysis revealed that this kind of cladding material could greatly reduce the oxidation thickness, the thermal performance of UO2–SiC was poor due to its low in-pile thermal conductivity and creep rate. Besides, the risk of failure exists when reactor power decreased. With geometry optimization and dopant addition in pellets, the steady-state performance of UO2–SiC was enhanced and the failure risk was reduced. The thermal and mechanical performance of the improved UO2–SiC was further evaluated under Loss of coolant accident (LOCA) and Reactivity Initiated Accident (RIA) conditions. Transient results showed that the optimized ATF had better thermal performance, lower cladding hoop stress, and could provide more coping time under accident conditions.

中文翻译：

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使用更新的 FROBA-ATF 代码对正常和事故条件下 SiCf/SiC 覆层的堆内行为进行评估

摘要 尽管 SiCf/SiC 复合包覆层由于其在高温蒸汽环境下抗氧化能力强等突出优点，作为下一代包覆材料的应用仍存在争议和不确定性，但不能否认 SiCf/SiC 复合包覆层是一种潜在的事故。具有高度研究优先级且目前仍处于工程设计阶段的耐燃料 (ATF) 包层。然而，考虑到其辐射热导率低、延展性几乎不存在等缺点，仍需要对其堆内行为进行进一步评估。本文基于我们最近更新的自主开发代码，应用 FROBA-ATF 中的相关热工水力和力学模型来模拟正常和事故工况下的熔覆行为。即使通过稳态性能分析表明这种包覆材料可以大大降低氧化厚度，但由于堆内热导率和蠕变率低，UO2-SiC的热性能很差。此外，反应堆功率下降时存在失效风险。通过几何优化和在颗粒中添加掺杂剂，UO2-SiC 的稳态性能得到增强，失效风险降低。在冷却剂损失事故 (LOCA) 和反应性引发事故 (RIA) 条件下，进一步评估了改进的 UO2-SiC 的热和机械性能。瞬态结果表明，优化后的 ATF 具有更好的热性能、更低的包层环向应力，并且可以在事故工况下提供更多的应对时间。