Abstract The purpose of this study is to define an envelope of possible transient conditions during two reactivity-initiated accidents (RIAs) in a modular high-temperature gas-cooled reactor (mHTGR). The accident scenarios studied were a group control rod withdrawal (CRW), a design basis accident, and a control rod ejection (CRE), a beyond design basis accident. Variance-based sensitivity analysis methods were employed to obtain realistic bounds on the reactor power and maximum temperature, energy deposition, and heating rate in the fuel during these accidents. Key reactor kinetic parameters and the heat transfer properties of the fuel and moderator were varied in a RELAP computer model of a 350-megawatt mHTGR to obtain these bounds. Sobol sensitivity indices were calculated to highlight which inputs account for the most variance in the outputs. Results showed that the kinetic properties and reactivity temperature coefficients were the most dominant inputs, while thermal properties had little impact on the outputs. Compared to previous experimental work, the fuel particle energy deposition from the simulated RIAs would not be expected to cause fuel failure in any design basis or beyond design basis reactivity accident we investigated. The predicted energy deposition in fuel kernels ranged from 98 to 331 J/g-fuel, significantly less than the expected failure threshold of approximately 1500 J/g-fuel. However, the power pulse widths and heating rates used in previous fuel safety experiments were different from the values predicted in this study for both accident scenarios. Regardless of these differences, this analysis shows that the safety margins in graphite-moderated mHTGRs for reactivity accidents are very large, and additional fuel safety tests are not expected to be necessary for this application.

中文翻译：

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定义高温气冷堆反应性引发事故的性能包线

摘要 本研究的目的是定义模块化高温气冷堆 (mHTGR) 中两次反应性引发事故 (RIA) 期间可能出现的瞬态条件的范围。研究的事故情景是控制棒退出（CRW）、设计基准事故和控制棒弹出（CRE）、超出设计基准事故。使用基于方差的灵敏度分析方法来获得这些事故期间反应堆功率和最高温度、能量沉积和燃料加热速率的实际界限。在 350 兆瓦 mHTGR 的 RELAP 计算机模型中改变关键反应器动力学参数以及燃料和慢化剂的传热特性以获得这些界限。计算 Sobol 敏感性指数以突出显示哪些输入导致输出中的最大差异。结果表明，动力学性质和反应温度系数是最主要的输入，而热性质对输出的影响很小。与之前的实验工作相比，在我们调查的任何设计基准或超出设计基准的反应性事故中，来自模拟 RIA 的燃料粒子能量沉积预计不会导致燃料失效。燃料内核中预测的能量沉积范围为 98 到 331 J/g-fuel，明显低于大约 1500 J/g-fuel 的预期失效阈值。然而，先前燃料安全实验中使用的功率脉冲宽度和加热速率与本研究中预测的两种事故情景的值不同。不管这些差异，