多群中子活化数据库能群结构对聚变堆停堆剂量率的影响研究

The fusion reactor is subjected to severe neutron irradiation, resulting in the frequently shut down for maintenance and replacement for the key components. Therefore, the calculation of the shutdown dose rate (SDDR) becomes an important issue in the design and safety analysis of the fusion reactor. The SDDR calculation is a multi-process neutronics calculation, involving activation and particle transport calculations. In this procedure, the activation calculation is the crucial step, which provides a source term for the transport calculation of decay photons produced by activated materials due to neutron irradiation. However, due to the fact that the energy group structure of multi-group data library will affect the accuracy and uncertainty of the grouped cross-sections, there are the significant differences for the activation reaction rate calculated with different energy groups, resulting in a large uncertainty of the final SDDR results, even the wrong results. Therefore, in this project, we are going to perform the study on the propagation of uncertainty of activation reaction rates due to the energy group in multi-process SDDR calculation, and analyze the impact of energy group of activation data library to SDDR, based on the “hybrid advanced D1S” with higher accuracy and efficiency. Subsequently combined with the conducted experiments on the SDDR benchmark for fusion reactors, the sensitive nuclides and energy groups which have great influence on the SDDR are found by the theoretical simulation analysis and experimental comparison. Finally, the high-precision adaptive multi-group activation data library will be established for them, which provides the foundation for future fusion reactor nuclear design and safety analysis.

聚变堆承受较为严重的中子辐照，相关部件需经常停堆维修更换，从而使得停堆剂量率计算成为聚变堆设计与安全分析中的一项重要内容。停堆剂量率计算是一个涉及活化、粒子输运计算的多过程中子学计算，其中活化计算为衰变光子输运计算提供源项。然而，由于多群数据库能群结构会影响分群截面的精度及不确定度，使得在活化计算中不同能群下活化反应率计算结果差异较大，从而导致最终停堆剂量率的计算结果具有较大不确定度，甚至出现错误的结果。因此，本项目拟基于具有较高效率和精度的“混合先进一步法”停堆剂量率计算方法，开展多群中子活化数据库能群结构对活化反应率不确定性在衰变光子源项计算及输运模拟中的传递研究，分析能群结构对停堆剂量率的影响。随后，结合已开展聚变堆停堆剂量率实验，通过理论模拟分析与实验对比，确定对停堆剂量率计算结果有较大影响的核素及能群，并针对其建立一套高精度的自适应多群中子活化截面数据库，为未来聚变堆核设计与安全分析奠定基础。

聚变堆承受较为严重的中子辐照，相关部件需经常停堆维修更换，从而使得停堆剂量率计算成为聚变堆设计与安全分析中的一项重要内容。停堆剂量率计算是一个涉及活化、粒子输运计算的多过程中子学计算，其中活化计算为衰变光子输运计算提供源项。然而，由于多群数据库能群结构会影响分群截面的精度及不确定度，使得停堆剂量率的计算结果具有较大不确定度。因此，重点开展了反应率积分量计算不确定性的研究，先后重点研究了基于蒙特卡罗粒子输运的反应率敏感性计算和不确定性计算的方法研究，随后基于该方法在蒙卡程序上进行实现，并采用国际基准题进行了分析。