Influence of implicit effect for multi-group cross-section perturbation on random-sampling-based uncertainty propagation

Fujita, Tatsuya  

Past studies have mentioned that the treatment of implicit effect for cross-section perturbation affects the sensitivity coefficients and then the uncertainty propagation for neutronics parameters. The several approaches to consider the implicit effect have also been discussed for the random-sampling-based uncertainty propagation. In this study, continued from the presentation in the AESJ 2024 spring meeting, the influence of implicit effect for multi-group cross-section perturbation on random-sampling-based uncertainty propagation was evaluated for the k-infinity uncertainty in the multi-group neutron transport calculation. While the influence of the implicit effect was small on the UO fuel pin-cell geometry, large influence was observed in the MOX fuel pin-cell geometry. However, it was considered that this influence could be reduced by refining the number of energy groups in neutron transport calculation and cross-section covariance matrix.