# 2019 Symposium on Nuclear Data 2019年度核データ研究会

28-30 November 2019
C-CUBE, Kyushu University Chikushi Campus 九州大学筑紫キャンパス総合研究棟 (C-Cube)
Asia/Tokyo timezone
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# Estimation of Covariance of Neutron Cross Sections for Decommissioning

## Speakers

• Mr. Tatsuki AMITANI

## Abstract

To optimize disposal of low-level radioactive waste generated from decommissioning of nuclear facilities, required are 1) reliable assessment of radioactivity level by calculation and measurement and 2) a good estimate of the uncertainty of those results for the classification of radioactive waste. However, uncertainties due to errors in cross-section data, one of the important input data for the calculations, have not been estimated in previous studies because of a lack of covariance data in many nuclei stored in JENDL-4. In this study, we estimated the covariance of neutron cross sections of $^{59}$Co and $^{62}$Ni, which are important nuclides for decommissioning, using a nuclear data evaluation code system T6 based on parameter distributions determined by a Bayesian Monte Carlo method. Special efforts were taken to adjust resonance and nuclear model parameters to reproduce cross sections of important reactions given in JENDL-4 so that we can estimate possible fluctuation around JENDL-4, and uncertainties of thermal cross sections given by Mughabghab.