Tremendous work has been done in the Light Water Reactor (LWR) Modelling and Simulation (M&S) uncertainty quantification (UQ) within the framework of the Organization for Economic Cooperation and Development (OECD)/Nuclear Energy Agency (NEA) LWR Uncertainty Analysis in Modelling (UAM) benchmark, which aims to investigate the uncertainty propagation in all M&S stages of the LWRs and to guide uncertainty and sensitivity analysis methodology development. The Best-Estimate Plus Uncertainty (BEPU) methodologies have been developed and implemented within the framework of the LWR UAM benchmark to provide a realistic predictive simulation capability without compromising the safety margins. This paper describes the current status of the methodological development, assessment, and integration of the BEPU methodology to facilitate the multiscale, multiphysics LWR core analysis. The comparative analysis of the results in the stand-alone multiscale neutronics phase (Phase I) is first reported for understanding the general trend of the uncertainty of core parameters due to the nuclear data uncertainty. It was found that the predicted uncertainty of the system eigenvalue is highly dependent on the choice of the covariance libraries used in the UQ process and is less sensitive to the solution method, nuclear data library, and UQ method. High-to-Low (Hi2Lo) model information approaches for multiscale M&S are introduced for the core single physics phase (Phase II). In this phase, the other physics (fuel and moderator), providing feedback to neutronics M&S in a LWR core, and time-dependent phenomena are considered. Phase II is focused on uncertainty propagation in single physics models which are components of the LWR core coupled multiphysics calculations. The paper discusses the link and interactions between Phase II to the multiphysics core and system phase (Phase III), that is, the link between uncertainty propagation in single physics on local scale and multiphysics uncertainty propagation on the core scale. Particularly, the consistency in uncertainty assessment between higher-fidelity models implemented in fuel performance codes and the rather simplified models implemented in thermal-hydraulics codes, to be used for coupling with neutronics in Phase III is presented. Similarly, the uncertainty quantification on thermal-hydraulic models is established on a relatively small scale, while these results will be used in Phase III at the core scale, sometimes with different codes or models. Lastly, the up-to-date UQ method for the coupled multiphysics core calculation in Phase III is presented, focusing on the core equilibrium cycle depletion calculation with associated uncertainties.

中文翻译：

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用于多尺度，多物理场轻水反应堆堆芯分析的最佳估计加上不确定性框架

在经济合作与发展组织（OECD）/核能机构（NEA）的框架内，轻水反应堆（LWR）建模和模拟（M＆S）不确定性量化（UQ）方面已进行了大量工作。LWR建模中的不确定性分析（UAM）基准，旨在研究轻水堆所有M＆S阶段的不确定性传播，并指导不确定性和敏感性分析方法的开发。最佳估计加不确定度（BEPU）方法已在LWR UAM基准框架内开发和实施，以提供现实的预测模拟功能，而不会损害安全裕度。本文介绍了BEPU方法论的方法学开发，评估和集成的现状，以促进多尺度，多物理场LWR核心分析。首次报道了对独立多尺度中子学阶段（第一阶段）的结果进行比较分析，以了解由于核数据不确定性而导致核心参数不确定性的总体趋势。发现系统特征值的预测不确定性高度依赖于UQ过程中使用的协方差库的选择，并且对求解方法，核数据库和UQ方法不那么敏感。针对核心单物理阶段（第二阶段）引入了用于多尺度M＆S的高到低（Hi2Lo）模型信息方法。在这个阶段，考虑了其他物理（燃料和慢化剂），它们向轻水堆堆芯中的中子学M＆S提供反馈，并考虑了与时间有关的现象。第二阶段的重点是单一物理模型中的不确定性传播，这些模型是LWR核心耦合多物理场计算的组成部分。本文讨论了第二阶段到多物理场核心与系统阶段（第三阶段）之间的联系和相互作用，即局部物理学中的单个物理学的不确定性传播与核心领域的多物理场的不确定性传播之间的联系。特别是，提出了在燃料性能规范中实施的高保真模型与在热工规范中实施的相当简化的模型之间不确定性评估的一致性，该模型将用于与中子学在第三阶段进行耦合。同样，热工液压模型的不确定性量化建立在相对较小的规模上，而这些结果将在核心规模的第三阶段中使用，有时使用不同的代码或型号。最后，提出了第三阶段耦合多物理场核心计算的最新UQ方法，重点是具有相关不确定性的核心平衡循环耗竭计算。