Abstract Usually, simulation tools are validated based on experimental data considering a best estimate simulation case; however, there is no quantification of this validation, which remains based on rough expert judgment. This technical note presents advanced validation treatment of the simulation tool OCARINa devoted to unprotected transient overpower (UTOP) accidents on two CABRI tests considering this time a Best Estimate Plus Uncertainty (BEPU) approach. The output results of interest are both scalar physical data such as the time and location of the pin failure and associated molten mass and vector data such as temperature axial distribution or temperature evolution versus time. This approach is a first step in quantifying the degree of agreement between the calculation results and the experimental results. It is of great interest for the verification, validation, and uncertainty quantification approach, which leads to the qualification of scientific calculation tools. Within the framework of the Generation IV Sodium-cooled Fast Reactor (SFR) research and development project in which the CEA is involved, OCARINa is a physical tool, relevant for performing preconceptual design studies and devoted to simulation of UTOP accidents on heterogeneous cores. Such accidents could not be simulated with mechanistic calculation tools such as SAS4A or SIMMER with their current capabilities; the thermomechanical models are not finalized in the SIMMER tool, and the SAS4A tool is validated only for homogeneous cores. The final objective aims at deriving the variability of the main results of interest to quantify the safety margins. The final use of the OCARINa tool being to perform sensitivity studies on the various possible sodium fast nuclear preconceptual core designs, the validation of this tool is first discussed at the pin scale (where separate-effects test measurements are available) based on statistical treatment. This enables one to determine the lacks and uncertainties of this tool. The modeling is then extended from local pin behavior to global core behavior adding a point-kinetics neutronic model. Final simulations of UTOP accidents caused by a uniform space reactivity ramp on an SFR core are realized taking into account the specificities of the pins of the various assemblies. The orders of magnitude of mechanical energy released are derived.

中文翻译：

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无保护瞬态超功率事故期间钠冷快堆销故障的高级研究和统计处理

摘要 通常，模拟工具的验证基于实验数据，考虑最佳估计模拟情况；然而，这种验证没有量化，它仍然基于粗略的专家判断。本技术说明介绍了模拟工具 OCARINa 的高级验证处理，该工具专门针对两次 CABRI 测试中的无保护​​瞬态过功率 (UTOP) 事故，同时考虑了最佳估计加不确定性 (BEPU) 方法。感兴趣的输出结果是标量物理数据，例如销故障的时间和位置以及相关的熔融质量和矢量数据，例如温度轴向分布或温度随时间的演变。这种方法是量化计算结果和实验结果之间的一致性程度的第一步。验证、确认和不确定性量化方法具有重要意义，这导致科学计算工具的资格。在 CEA 参与的第四代钠冷快堆 (SFR) 研究和开发项目的框架内，OCARINa 是一种物理工具，与执行概念前设计研究相关，并致力于模拟异构堆芯上的 UTOP 事故。此类事故无法使用 SAS4A 或 SIMMER 等机械计算工具以目前的能力进行模拟；热机械模型未在 SIMMER 工具中最终确定，SAS4A 工具仅针对同质核心进行验证。最终目标旨在推导出感兴趣的主要结果的可变性，以量化安全裕度。OCARINa 工具的最终用途是对各种可能的钠快核概念前核心设计进行敏感性研究，首先在基于统计处理的引脚规模（其中可以使用单独效应测试测量）讨论该工具的验证。这使人们能够确定该工具的不足和不确定性。然后将建模从局部引脚行为扩展到全局核心行为，添加点动力学中子模型。考虑到各种组件的引脚的特性，实现了由 SFR 核心上的均匀空间反应性斜坡引起的 UTOP 事故的最终模拟。推导出所释放机械能的数量级。该工具的验证首先在基于统计处理的引脚规模（其中单独效应测试测量可用）进行讨论。这使人们能够确定该工具的不足和不确定性。然后将建模从局部引脚行为扩展到全局核心行为，添加点动力学中子模型。考虑到各种组件的引脚的特性，实现了由 SFR 核心上的均匀空间反应性斜坡引起的 UTOP 事故的最终模拟。推导出所释放机械能的数量级。该工具的验证首先在基于统计处理的引脚规模（其中单独效应测试测量可用）进行讨论。这使人们能够确定该工具的不足和不确定性。然后将建模从局部引脚行为扩展到全局核心行为，添加点动力学中子模型。考虑到各种组件的引脚的特性，实现了由 SFR 核心上的均匀空间反应性斜坡引起的 UTOP 事故的最终模拟。推导出所释放机械能的数量级。然后将建模从局部引脚行为扩展到全局核心行为，添加点动力学中子模型。考虑到各种组件的引脚的特性，实现了由 SFR 核心上的均匀空间反应性斜坡引起的 UTOP 事故的最终模拟。推导出所释放机械能的数量级。然后将建模从局部引脚行为扩展到全局核心行为，添加点动力学中子模型。考虑到各种组件的引脚的特性，实现了由 SFR 核心上的均匀空间反应性斜坡引起的 UTOP 事故的最终模拟。推导出所释放机械能的数量级。