A novel method for rapid calculation of moderated neutron spectrum and its application in deep penetration

Abstract

The moderated neutron spectrum has an essential influence on the neutronics experimental studies and the neutron transport simulation method (such as Monte Carlo method) is one of the important methods for the calculation of it. The Monte Carlo method is characterized by its high accuracy, however, it will bring high time-consuming problems, and it is difficult to converge in the case of deep penetration. In this research, a novel method for rapid calculation of moderated neutron spectrum was developed. It used the Monte Carlo method to decompose typical shielding materials into a library according to a fixed thickness and calculated the multi-dimensional response matrix corresponding to the shielding module. With adjustment of its thickness, the moderated neutron spectrum was able to be calculated through matrix operation. The proposed method was verified under the moderator composed of shielding modules of different numbers, thickness and materials by comparing with the results of the Monte Carlo algorithm. The results stated the moderated neutron spectrum calculated by this method and Monte Carlo algorithm reached the order of 1.000E−06 on the MSE. Furthermore, the proposed method was verified with a simplified thermal reactor TRIGA in the case of deep penetration. The results showed that the moderated neutron spectrum in the convergent energy range of the two methods also performed well, and in the non-convergent energy range, the proposed method could give a heuristic neutron spectrum.