The maximum fuel temperature under accident condition is the most important parameter of inherently safe characteristics of HTR-PM, and the DLOFC accident may lead to a peak accident fuel temperature. And there are a variety of uncertainty sources in the maximum fuel temperature calculations, and thus the contributions of these uncertainty sources to the final calculated maximum fuel temperature should be quantified to check whether the peak value exceed the technological limit of 1620°C or not. Eight uncertainty input parameters are selected for inclusion in this uncertainty study, and their associated 2 standard deviation uncertainties and probability density functions are specified. Then, the DLOFC thermal analyses and uncertainty analysis are performed with the home-developed ATHENA and CUSA. The numerical results indicate that the pebble-bed effective conductivity and the decay heat contribute the most of the uncertainty in the DLOFC maximum fuel temperature while this peak fuel temperature is most sensitive to the initial reactor power and the decay heat. In short, uncertainties in these selected eight parameters lead to the two standard deviation (2σ) uncertainty of ±77.6°C (or 5.2%) around the mean value of 1493°C for the maximum fuel temperature under DLOFC accident of HTR-PM. At the same time, the LHS-SVDC method of CUSA is recommended to propagate uncertainties in inputs and 100–200 model simulations seem to be sufficient to get an uncertainty prediction with full confidence.

中文翻译：

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HTR-PM事故工况下最高燃油温度的灵敏度和不确定度分析

事故条件下的最高燃油温度是HTR-PM本质安全特性的最重要参数，而DLOFC事故可能会导致事故燃油温度达到峰值。最高燃料温度计算中存在多种不确定性来源，因此应量化这些不确定性来源对最终计算出的最高燃料温度的贡献，以检查峰值是否超过1620°C的技术极限。选择了八个不确定性输入参数以包含在此不确定性研究中，并指定了它们相关的2个标准偏差不确定性和概率密度函数。然后，使用自制的ATHENA和CUSA进行DLOFC热分析和不确定性分析。数值结果表明，卵石床有效电导率和衰减热是DLOFC最高燃料温度的最大不确定因素，而峰值燃料温度对初始反应堆功率和衰减热最为敏感。简而言之，这8个选定参数的不确定性导致两个标准差（2σ）在HTR-PM的DLOFC事故下最高燃油温度的1493°C平均值附近，不确定性为±77.6°C（或5.2％）。同时，建议使用CUSA的LHS-SVDC方法在输入中传播不确定性，并且100–200模型仿真似乎足以完全确定不确定性。