Development of burnup calculation method based on neutron spectrum reconstruction with POD, 3; Implementation of multi-group effective cross-section calculations and verification using a 361-group energy structure

Watanabe, Tomoaki  ; Aizawa, Naoto*; Chiba, Go*; Tada, Kenichi   ; Fujita, Tatsuya*; Yamamoto, Akio*

We currently propose a fast burnup calculation method using a low-dimensional neutron spectrum prediction model based on Proper Orthogonal Decomposition (POD). In previous studies, the impact of prediction errors in the neutron spectrum on nuclide inventory estimates has been considered; however, the multi-group effective cross-section calculation used to derive energy-averaged cross sections from the neutron spectrum had not yet been addressed. In this study, we incorporated the multi-group effective cross-section calculation into the proposed method and evaluated the overall computational accuracy. As a result, it was confirmed that the impact of the multi-group effective cross-section calculation on the accuracy of nuclide inventory is sufficiently small. Furthermore, a comparative analysis was conducted using both 172-group and 361-group energy structures, and it was found that employing the finer 361-group structure improves the calculation accuracy for several fission product nuclides.