Abstract

In a companion paper, the U.S. Nuclear Regulatory Commission (NRC) staff has described analyses performed using the TRAC/RELAP Advanced Computational Engine (TRACE) code to study the transient system response of the NuScale power module to a postulated beyond-design-basis loss of alternating-current (LOAC) power transient where the module protection system completely fails to insert the control rods. The subject paper studies the sensitivity of the event progression and consequences to variation in the initial reactor coolant system (RCS) temperature. These studies were performed by varying the effective steam generator heat transfer surface area between 100% and 50% of the nominal area. The results of the NRC staff analyses show that at increased initial temperatures, it is possible for the NuScale primary side to remain critical for an extended period of time, leading to a sustained loss of primary-side inventory through pressure relief until the natural circulation flow pattern in the RCS becomes broken. After the flow loop is broken, reactor power decreases significantly, and the primary figures of merit important to safety are met with substantial margin.

摘要

在随附的论文中，美国核监管委员会（NRC）的工作人员描述了使用TRAC / RELAP高级计算引擎（TRACE）代码执行的分析，以研究NuScale电源模块对假定的超出设计基准的损耗的瞬态系统响应。其中模块保护系统完全无法插入控制杆的交流电（LOAC）功率瞬变。该主题文件研究了事件进展的敏感性以及对初始反应堆冷却剂系统（RCS）温度变化的后果。这些研究是通过在有效蒸汽发生器的传热表面积在标称面积的100％到50％之间变化来进行的。NRC人员分析的结果表明，在初始温度升高的情况下，NuScale初级侧可能会在很长一段时间内保持关键状态，从而通过泄压导致初级侧存量的持续损失，直到RCS中的自然循环流模式被破坏为止。流动回路中断后，反应堆功率将显着下降，并且对安全重要的主要性能指标将获得可观的利润。