Judgment on convergence-in-distribution of Monte Carlo tallies under autocorrelation

Ueki, Taro

Nuclear Science and Engineering, 194(6), p.422 - 432, 2020/06

https://doi.org/10.1080/00295639.2019.1710418

In Monte Carlo criticality calculation, the convergence-in-distribution check of the sample mean of tallies can be approached in terms of the influence range of autocorrelation. In this context, it is necessary to evaluate the attenuation of autocorrelation coefficients over lags. However, in just one replica of calculation, it is difficult to accurately estimate small ACCs at large lags because of the comparability with statistical uncertainty. This paper proposes a method to overcome such an issue. Its essential component is the transformation of a standardized time series of tallies so that the resulting series asymptotically converges in distribution to Brownian motion. The convergence-in-distribution check is constructed based on the independent increment property of Brownian motion. The judgment criterion is set by way of the spectral analysis of fractional Brownian motion. Numerical results are demonstrated for extreme and standard types of criticality calculation.

Evaluation of the analytical errors jn plutonium and uranium isotopic composition analysis based on routine control measurement data (1998/92000/12)

Kobayashi, Hideo; ; ; ; ; *; *

JNC TN8440 2001-005, 33 Pages, 2001/02

JNC-TN8440-2001-005.pdf:1.24MB

Four mass spectrometers are used for plutonium and uranium isotopic composition analysis in the Plutonium Fuel Center. Analytical errors of the analysis was evaluated based on routine control data obtained with measurement of reference materials. It was confirmed that the errors satisfied the International Target Values for safeguard analysis, and the random error of the analysis was improved by changing conventional method to total evaporation method.