核数据处理软件NECP-Atlas中的光子相关数据计算方法研究

NECP-Atlas是西安交通大学自主研制的核数据处理软件，具有丰富的功能，可将评价核数据制作为后续核设计所需的应用核数据库，本文在NECP Atlas中建立了光子相关数据的计算方法，可计算产生中子核反应释放的瞬发光子产生截面、光子与原子的反应截面，裂变产物衰变释放的缓发光子多群产生矩阵，以及光子辐照损伤截面等数据。数值结果显示，如果不考虑缓发光子，钠冷快堆中控制组件、反射层组件的光子功率与参考解的最大偏差可达3258%、2041%，采用NECP Atlas计算的多群缓发光子产生矩阵后两类组件偏差降为093%以下。采用文献结果对Fe的光子辐照损伤截面进行了验证，计算结果与参考解吻合良好。

Research on Generation Method for Photon-related Data in Nuclear Data Processing Code NECP-Atlas

The nuclear data processing code NECP-Atlas, developed at Xi’an Jiaotong University, has various functions to process the evaluated nuclear data to generate the applied nuclear data library for the nuclear reactor designs. In this paper, the photon related data generation capacities were developed in NECP Atlas, including the photon production cross sections and photon irradiation cross sections. In the conventional nuclear data processing code such as NJOY, only the production cross section for the prompt photon released with the neutron induced reactions, and the photon atom reaction cross section can be produced, while the delayed photon released by the fission products is ignored regardless of its large contribution for the heating of the regions without fissionable materials such as control and reflector assemblies in fast neuron reactors. In this paper, the capacity for the generation of the production cross section for the delayed photon was developed in NECP Atlas. Besides, in the conventional nuclear data processing code, only the neutron irradiation damage cross section can be generated, while in the practical reactors, electron and positron also cause significant irradiation damage. The photon atom reactions, including Compton scattering, pair production and photoelectric effect, emit electron and positron. Therefore, the photon can also cause irradiation damage. To satisfy the demands from various application aspects, the capacity for the calculation of the photon irradiation damage cross sections was also developed in NECP Atlas. Meanwhile, the electron and positron irradiation damage cross section can also be produced, because it is the basis for the calculation of photon irradiation damage cross section. The delayed photon production cross sections were tested on the EBR Ⅱ fast reactor, and the results were compared with the library of the ERANOS which includes the production cross section of delayed photon. The difference of photon heating calculated based on the two libraries respectively from NECP Atlas and ERANOS is less than 0.93%, which means the correctness of the delayed photon data produced by NECP Atlas. Besides, the numerical results show that if the delayed photon is ignored, the difference of photon heating for the control assembly and reflector assembly can reach 3258% and 2041%, compared with the results of considering the delayed photon. The electron and positron displacement damage cross sections of Fe and Au calculated by NECP Atlas were verified with the results published by Oka Ridge National Laboratory, and the photon displacement cross sections calculated by NECP Atlas were verified with results reported by other researches. The numerical results show good agreement with the reference results.