Abstract The Virtual Environment for Reactor Applications (VERA) Core Physics Benchmark Progression problems #1 to #10 based on the 17 × 17 Pressurized Water Reactor (PWR) Watts Bar Unit 1 designed by Westinghouse have been proposed by the Consortium for Advanced Simulations of Light Water Reactors (CASL) as core physics benchmarks. These problems were selected to assist nuclear software and methods developers to develop the capabilities needed to accurately model nuclear power reactors. These problems have 10 different conditions ranging from a simple 2D pin cell to the full core time-dependent depletion. VERA Problem #8, Physical Reactor Flux Maps, describes the first 48 h of a reactor startup with the power gradually increasing from 0% to 100% including the control rod movements which must be considered. This problem was solved in this study using the continuous energy Monte Carlo code RMC coupled with the subchannel thermal-hydraulics code CTF in a hybrid computational strategy. The effects of axial-layering on the solutions were studied with the model divided into 10 layers in the axial direction with the analyses considering both the cost and the accuracy with VERA Problem #8 simulated on the Tianhe II supercomputer. A large number of particles was simulated to get a reliable solution with the mean uncertainty in the power distribution reduced to about 2.6% for all the 526,640 burnup regions for each iteration between RMC and CTF. The eigenvalue trajectory of the critical boron concentration during the startup was provided with the predicted k eff which differs from the common continuous decline. The RMC/CTF code also gives a 3D view of the relative power density distribution and the relative uncertainty distribution at three typical time points and the subchannel outlet temperatures whose peak locations are consistent with the radial power distribution. The RMC/CTF solution is the first published coupled Monte Carlo neutronics/subchannel thermal hydraulics solutions for Problem #8.

中文翻译：

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RMC/CTF 多物理场解决方案 VERA 核心物理基准问题 #8

摘要 The Virtual Environment for Reactor Applications (VERA) Core Physics Benchmark Progression questions #1 to #10 基于由 Westinghouse 设计的 17 × 17 压水反应堆 (PWR) Watts Bar Unit 1 已由 Consortium for Advanced Simulations of Light 提出水反应堆 (CASL) 作为核心物理基准。选择这些问题是为了帮助核软件和方法开发人员开发准确模拟核动力反应堆所需的能力。这些问题有 10 种不同的条件，从简单的 2D pin cell 到完整的内核时间相关耗尽。VERA 问题 #8，物理反应堆通量图，描述了反应堆启动的前 48 小时，功率从 0% 逐渐增加到 100%，包括必须考虑的控制棒运动。在本研究中，使用连续能量蒙特卡罗代码 RMC 与子通道热工水力代码 CTF 结合在混合计算策略中解决了这个问题。研究了轴向分层对解的影响，模型在轴向上分为 10 层，并在天河 II 超级计算机上模拟了 VERA 问题 #8，同时考虑了成本和精度。模拟大量粒子以获得可靠的解决方案，对于 RMC 和 CTF 之间的每次迭代，所有 526,640 个燃尽区域的功率分布的平均不确定性降低到约 2.6%。启动过程中临界硼浓度的特征值轨迹提供了与常见的连续下降不同的预测 k eff 。RMC/CTF 代码还给出了三个典型时间点的相对功率密度分布和相对不确定度分布的 3D 视图，以及峰值位置与径向功率分布一致的子通道出口温度。RMC/CTF 解决方案是第一个发布的针对问题 #8 的耦合蒙特卡罗中子学/子通道热液压解决方案。