Evaluation of Uncertainties for the Prompt Fission Neutron Spectrum and Average Neutron Multiplicity using the Los Alamos Model

摘要

Recently, there has been an increased need for uncertainty quantification including covariance matrices of important nuclear data for use in the reactor physics community. Some of this important nuclear data includes cross sections, prompt and delayed fission spectra, and average fission neutron multiplicities and fission neutron multiplicity distributions. While much work has been devoted to the precise evaluation of cross sections, it has been assumed for a long time that uncertainties in fission neutron spectra would have a negligible impact on applications. However, in some selected integral benchmarks, recent estimates of the neutron fission spectrum uncertainties have been shown to be as important as cross section uncertainties. Partially due to these results from the selected integral benchmarks and because many of the actinides in the ENDF/B-VII.0 library have very little or zero evaluated prompt fission spectrum data and even more limited covariance data, this research will focus on the evaluation of uncertainties of the prompt fission neutron spectrum (PFNS) and the average prompt fission neutron multiplicity (PFNM) for all relevant actinides.