In order to improve the reliability and accuracy of Monte Carlo code in the critical safety calculation of loosely coupled systems,it is necessary to determine the source convergence of the results.In this paper,an improved Shannon entropy diagnose method considering the distribution of fission sources and the statistical deviation weight factor is proposed.The relative deviation of fission sources distribution between adjacent generations and the standard deviation of fission source distribution during source iteration are used as the weight of fission source distribution.Finally,an improved Shannon entropy convergence index is established,which makes up for the shortcomings of traditional Shannon entropy for lacking the details of local fission source.The improved Shannon entropy convergence index is applied to the benchmark problem:spent fuel rod and loosely coupled solution slabs published by OECD/NEA.The results show that compared with the traditional Shannon entropy index,the improved Shannon entropy is more sensitive to the iterative convergence process of fission source,and can more intuitively and accurately determine the convergence of fission source distribution accompanied by source iteration.For a typical case with slow convergence speed,the conclusion of pseudo-convergence is given with the traditional Shannon entropy.The improved Shannon entropy can accurately determine the number of iterations when the source iteration reaches convergence.
维普
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