PWR核电厂乏燃料贮存临界计算重要核素的选取

信用核素选取是基于燃耗信用制乏燃料贮存临界安全分析的关键一步。通过对不同富集度、燃耗深度及停堆冷却时间下典型PWR燃料组件分析,以核素中子吸收份额大小排序为依据,筛选出对总的中子吸收起主要贡献的核素。结果显示,47个核素即可包络停堆后0~20a内影响乏燃料贮存系统反应性的所有核素中的99%。通过核素敏感性因子分析证明依据中子吸收份额排序选取重要核素的方法是合理的,与基准算例的结果对比证明所筛选出的核素能足够代表影响系统反应性的所有重要核素。

Important Nuclide Selection Based on Spent Fuel Storage Criticality Calculation for PWR Nuclear Power Plant

The credit nuclide selection is the key step in burnup credit for spent fuel storage criticality safety analysis. Based on typical PWR fuel assembly with different enrichment, burnup and cooling time combinations, important nuclides in criticality safety analysis were selected according to nuclide importance ranking in terms of their fractional neutron absorptions. The results show that 47 nuclides can bound 99% nuclides which affect the spent fuel storage system reactivity during 0.20 a after shutdown. The validation analysis shows that the selection method is reasonable and the selected nuclides can adequately represent all dominant nuclides in system reactivity calculation.