Yuanzineng kexue jishu (May 2022)
Reaction Cross Section and Covariance Evaluation of 56Fe(n,p)56Mn below 35 MeV
Abstract
Neutron induced reaction cross sections play an important role in nuclear science and technology research, such as national defense, nuclear energy construction and development, nuclear medicine, radiation protection and nuclear safety. With the rapid development of nuclear technology, there are increasing demand for the variety and accuracy of neutron data. As an important structure material nuclide, the accuracy of neutron induced reaction cross section on 56Fe is directly related to the design and operation of reactors, spent fuel disposal and miniaturization design, and also of great significance to nuclear physics basic research. The 56Fe(n,p)56Mn reaction is usually used as the standard to monitor the neutron field flux in the experiment. It greatly influences the results of nuclear data measurement, and also has guiding significance for upon carry the determination of the parameters in the nuclear reaction model. Due to the obvious differences existing in the previous experimental data and inconsistency between the evaluation databases, the experimental measurement data evaluation and covariance analysis were carried out for the 56Fe(n,p)56Mn reaction cross section in this paper. Firstly, the existing experimental measurement data of 56Fe(n,p)56Mn reaction cross section in EXFOR and literature were downloaded and systematically collected, then summarized, contrasted, and classified in terms of neutron source, measurement method, detector kinds, etc. Secondly, the data with low reliability were discarded with checking the original papers, and the uncertainty mentioned in these papers was also analyzed. Additionally, previous experimental results which using the imprecise values were adjusted and modified with the more accurate data such as recently ratios, supervised reaction standard cross sections, and isotopic abundances. The data with significant divergence near 14 MeV were normalized, which made it more concentrated and less divergent. The polynomial curve fitting was applied to obtain the excitation curve of 56Fe(n,p)56Mn reaction between 29535 MeV which was derived from the corrected and normalized results. Following that, the correlation covariance matrix was calculated for the suggested experimental data after evaluation. Meanwhile, the energy density, optical potential parameters, energy level density parameters, and other parameters of 56Fe(n,p)56Mn reaction were adjusted within the physical model calculated by the nuclear reaction simulation program TALYS. Finally, the reaction cross section of 56Fe(n,p)56Mn was computed theoretically, compared with experimental data and evaluation databases. This paper broadened the existing evaluation method of neutron activation reaction cross section experimental data, and also improved the accuracy of the assessment data for neutroninduced 56Fe(n,p)56Mn reaction cross section measured data below 35 MeV. The recommended assessment value and its covariance of the 56Fe(n,p)56Mn reaction excitation function were given based on the evaluted results of experimental data. Excitation function input file for 56Fe(n,p)56Mn reaction derived by adjusting the TALYS parameters agree well with the experimental and evaluation data. A set of standard assessment techniques were constructed, which serves as a guide for theoretical calculation and database construction of related nuclear data.
