Temperature majorant cross sections in Monte Carlo neutron tracking
نویسندگان
چکیده
This article discusses the generation of temperature majorant cross sections, the type of cross sections required by two separate techniques related to Monte Carlo neutron tracking, namely the Doppler-broadening rejection correction (DBRC) and Target Motion Sampling (TMS) temperature treatment methods. In the generation of these cross sections the theoretically infinite range of thermal motion must be artificially limited by applying some sort of a cut-off condition, which affects both the accuracy and the performance of the calculations. In this article, a revised approach for limiting the thermal motion is first introduced and, then, optimal cut-off conditions are determined for both the traditional majorant, commonly used in DBRC implementations and old implementations of the TMS method, and the revised majorant. It turns out that using the revised type of temperature majorant cross sections increases the performance of the TMS method slightly, but no practical difference is observed with the DBRC method. It is also discovered that in ordinary reactor physical calculations the cut-off conditions originally adopted from the SIGMA1 Doppler-broadening code can be significantly relieved without compromising the accuracy of the results. By updating the cut-off conditions in the majorant generation, the CPU time requirement of Serpent 2.1.17 is reduced by 8–23 % in TMS calculations and by 1–6 % in problems involving DBRC.
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