Abstract

The U.S. Nuclear Regulatory Commission (NRC) staff often performs confirmatory analysis to support regulatory decision making. In the current work the TRAC/RELAP Advanced Computational Engine (TRACE) code was used to study the transient system response for the NuScale power module to a beyond-design-basis event where the control rods fail to insert. The regulatory purpose of the current work was to confirm the results of analyses provided by the applicant as part of their probabilistic risk assessment analysis that demonstrates that the core is not damaged under certain conditions when the control rods fail to insert. The NRC staff performed calculations using a TRACE model of the NuScale power module that includes both the primary and secondary systems that simulates a loss of alternating-current power and complete failure of the module protection system to insert control rods. The NRC staff analyses demonstrate that under these conditions the reactor stabilizes at a new stable condition with minor power and pressure oscillations where core power is balanced by passive heat removal.

摘要

美国核监管委员会（NRC）的工作人员经常进行确认分析，以支持监管决策。在当前工作中，TRAC / RELAP高级计算引擎（TRACE）代码用于研究NuScale功率模块对超出控制杆无法插入的超设计基准事件的瞬态系统响应。当前工作的监管目的是确认申请人提供的分析结果，作为其概率风险评估分析的一部分，该结果表明，在某些情况下，当控制棒无法插入时，岩心没有损坏。NRC人员使用NuScale功率模块的TRACE模型进行了计算，该模型包括一次和二次系统，该系统模拟交流功率的损失以及模块保护系统插入控制杆的完全故障。NRC的工作人员分析表明，在这些条件下，反应堆稳定在新的稳定条件下，功率和压力波动较小，而堆芯功率通过被动排热得到平衡。