Impact of incident energy dependence of prompt fission neutron spectra on uncertainty analyses

This paper investigates the impact of the incident energy dependence of prompt fission neutron spectra (PFNS) on uncertainty propagation calculations. Uncertainty propagation from incident energy-dependent PFNS to criticality is formulated and its impact is evaluated numerically. It is found that the conventional procedure, in which representative PFNS covariance data for a specific incident energy are used, results in a large PFNS-induced uncertainty than the straightforward procedure, in which different PFNS covariance data are used for each incident energy range given in the nuclear data libraries. The present study suggests that the correlation between different incident energies of PFNS has a large impact on uncertainty propagation calculation results for nuclear characteristics. (author)