20MeV以下快中子诱发56Fe非弹性散射截面的分歧研究

Inelastic scattering cross-section for neutron-induced 56Fe is particularly important as it represents the main neutron energy loss mechanism and therefore a good knowledge of the cross sections is essential for the safety, the size and consequently the cost of the newly developed facilities. So far, there are great differences (~35%) between the macroscopic examination results and the microscopic results for the inelastic cross section of 56Fe. The difference among the numerous available experimental results remain significant and largely unexplained. In this work, the method of converting experimental data from gamma-ray production to inelastic cross section will be established and new experimental information for inelastic cross section will be obtained. Moreover, the simultaneous evaluated technology will be developed in this work to analyze the experimental data for each nuclear reactions and assure the consistency of the results. Meantime, a detail model theoretical calculation will be performed with UNF code. Finally, a good overall agreement was found with the previous evaluation. It will offer an important basis for clarifying the differences between the Fe ball macroscopic examination results and microscopic data. The accurate cross sections obtained in this work are an important step towards improved accuracy estimates in neutron transport calculations.

在核装置中，中子与56Fe的非弹性散射是中子能量损失的主要机制，因此56Fe的快中子非弹性散射截面的精度对于新型核装置的设计具有重要的意义，关系到装置的安全性、可靠性、以及建造和维护成本。然而，到目前为止，该截面的宏观检验结果与微观结果仍然存在很大的分歧，最大分歧处达到35%，并且微观实验之间及理论模型结果之间也存在很大分歧。本项目拟结合微观的实验测量，建立目前国际上正在研究，而国内尚未涉足的利用第一非弹伽玛产生数据的实验测量数据获得非弹截面的方法及多个反应道实验数据的同时评价技术，同时从核反应理论出发，开展模型计算分析来确保理论的自洽，并结合Fe球宏观测量实验的结果，对56Fe非弹截面的分歧的原因进行系统性的研究，澄清数据分歧，获得较为可靠的56Fe的快中子非弹性散射截面，为新型核能系统研发及核装置设计服务。

56Fe的非弹性散射截面在核装置中子输运计算中扮演着重要的角色，但无论从实验数据还是从评价数据，非弹性散射截面都存在很大分歧，它的数据直接影响到核装置的设计、建造与运行维护。本工作从实验数据本身出发，深入分析了不同实验室测得的847-keV 的γ 产生截面的分歧，经转化后补充非弹性散射截面的实验空白能区，并同时利用满足全截面、去弹截面等截面自洽关系的评价方法推荐了高精度的快中子与56Fe的非弹反应截面结果。积分检验表明，新的非弹截面的改进使得评价数据与积分实验结果一致，较CENDL-3.1的评价数据结果有显著改善。