Abstract

Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was a prototype for the U.S. National Aeronautics and Space Administration’s Kilopower Program. KRUSTY has a highly enriched uranium–molybdenum alloy (with 7.65 wt% molybdenum) annular core reflected by beryllium oxide with an outer stainless steel shield. Five configurations from the experimental campaign were chosen to be evaluated as benchmark cases. Uncertainties were evaluated in five categories: (1) criticality measurement, (2) mass and density, (3) dimensions, (4) material compositions, and (5) positioning. The largest contribution to the overall uncertainty in each case was from the radial alignment of the movable platen. A simplified model was created to increase computational efficiency, and an average bias of –16 pcm was calculated due to the simplifications. Sample calculations were completed for each case using MCNP6.2, COG, and MC21, all with ENDF/B-VIII.0 nuclear data. For MCNP6.2, the average difference (absolute value) between the calculated and experimental k_eff for the five configurations was 14 pcm for both the detailed and the simplified models. The k_eff results from all three codes are within 1σ of the benchmark values. KRUSTY’s value as a benchmark is due to its sensitivity to beryllium and molybdenum. For beryllium, KRUSTY adds an 18th benchmark with a total cross-section sensitivity greater than 0.05%/%/(unit lethargy). For molybdenum, KRUSTY adds a 9th benchmark with a total cross-section sensitivity greater than 0.004%/%/(unit lethargy).

摘要

使用斯特林技术的千瓦级反应堆 (KRUSTY) 是美国国家航空航天局千功率计划的原型。KRUSTY 有一个高浓缩铀钼合金（含 7.65 wt% 钼）环形核心，由氧化铍反射，外部不锈钢护罩。选择来自实验活动的五种配置作为基准案例进行评估。在五个类别中评估不确定性：（1）临界测量，（2）质量和密度，（3）尺寸，（4）材料成分和（5）定位。在每种情况下，对整体不确定性的最大贡献来自可移动压板的径向对齐。创建了一个简化模型以提高计算效率，由于简化，计算出的平均偏差为 –16 pcm。使用 MCNP6.2、COG 和 MC21 完成每个案例的样本计算，所有这些都使用 ENDF/B-VIII.0 核数据。对于 MCNP6.2，计算和实验 k 之间的平均差值（绝对值）_{对于详细模型和简化模型，五种配置的eff}均为 14 pcm。所有三个代码的 k _eff结果都在基准值的 1σ 以内。KRUSTY 作为基准的价值在于它对铍和钼的敏感性。对于铍，KRUSTY 添加了第 18 个基准，总横截面灵敏度大于 0.05%/%/（单位嗜睡）。对于钼，KRUSTY 增加了第 9 个基准，总横截面灵敏度大于 0.004%/%/（单位嗜睡）。