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Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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ANS joins others in seeking to discuss SNF/HLW impasse
The American Nuclear Society joined seven other organizations to send a letter to Energy Secretary Christopher Wright on July 8, asking to meet with him to discuss “the restoration of a highly functioning program to meet DOE’s legal responsibility to manage and dispose of the nation’s commercial and legacy defense spent nuclear fuel (SNF) and high-level radioactive waste (HLW).”
Taro Ueki
Nuclear Science and Engineering | Volume 160 | Number 2 | October 2008 | Pages 242-252
Technical Paper | doi.org/10.13182/NSE160-242
Articles are hosted by Taylor and Francis Online.
The stationarity diagnostics of source distribution in the iterated-source Monte Carlo computation for nuclear criticality and static nuclear reactor analysis have been studied using relative entropy and the Wilcoxon signed rank sum. Novel aspects of the diagnostics are (a) the relative entropy of permuted and nonpermuted source distributions and (b) a series of differenced relative entropies. Item (a) combined with averaging over random permutations has some smoothing effect on the fluctuation through iteration cycles. The benefit of item (b) is twofold: The differencing works as decorrelation, and the mean in stationarity of a differenced series is exactly zero. Therefore, the Wilcoxon signed rank sum has been applied to check the stationarity of the differenced relative entropy series. Another novel aspect of the diagnostics is the use of a problem-independent number of iteration cycles preceding the current iteration cycle upon the computation of the Wilcoxon signed rank sum. In addition, it has been shown that the progressive relative entropy in previous work can be used and the moving average of the Wilcoxon signed rank sums of its differenced series is a stringent measure of stationarity. Numerical results are presented for two- and three-dimensional modeling of an initial core of pressurized water reactors.