The “best-estimate plus uncertainty” (BEPU) methodology is the term used in the nuclear engineering community when dealing with uncertainty quantification issues in realistic numerical simulation models. One of the most critical hypothesis in these studies is the choice of the probability distributions of uncertain input variables which are propagated through the model. Bringing stringent justifications to the BEPU approach, especially in a safety study, requires quantifying the impact of potential uncertainty on the input variable distribution. To solve this problem, this paper deepens the robustness analysis based on the “Perturbed Law-based sensitivity Indices” (PLI). The PLI quantifies the impact of a perturbation of an input distribution on the quantity of interest (as a quantile of a model output or a safety margin) in the BEPU study. The mathematical formalism of the PLI is applied to two particular quantities of interest: the quantile and the superquantile. For both quantities, the PLI can be easily computed using a unique Monte-Carlo sample containing model inputs and output. Numerical tests are developed in order to define validity criteria of a PLI-based robustness analysis. The practical use of the method is illustrated on thermal-hydraulic computer experiments, simulating a cold leg Intermediate Break Loss Of Coolant Accident (IBLOCA) in a pressurized water nuclear reactor.

“最佳估计加不确定性”(BEPU) 方法是核工程界在处理现实数值模拟模型中的不确定性量化问题时使用的术语。这些研究中最关键的假设之一是选择通过模型传播的不确定输入变量的概率分布。为 BEPU 方法提供严格的理由，尤其是在安全研究中，需要量化潜在不确定性对输入变量分布的影响。针对这一问题，本文基于“扰动法敏感性指数”（PLI）深化了稳健性分析。PLI 量化了输入分布的扰动对 BEPU 研究中感兴趣的数量（作为模型输出的分位数或安全裕度）的影响。PLI 的数学形式适用于两个特定的感兴趣的量：分位数和超分位数。对于这两个数量，可以使用包含模型输入和输出的独特蒙特卡罗样本轻松计算 PLI。开发数值测试是为了定义基于 PLI 的稳健性分析的有效性标准。该方法的实际应用在热工水力计算机实验中得到了说明，模拟了压水核反应堆中的冷段中间断流冷却剂事故 (IBLOCA)。开发数值测试是为了定义基于 PLI 的稳健性分析的有效性标准。该方法的实际应用在热工水力计算机实验中得到了说明，模拟了压水核反应堆中的冷段中间断流冷却剂事故 (IBLOCA)。开发数值测试是为了定义基于 PLI 的稳健性分析的有效性标准。该方法的实际应用在热工水力计算机实验中得到了说明，模拟了压水核反应堆中的冷段中间断流冷却剂事故 (IBLOCA)。