Fe-56, O-16, H-1 Elastic and capture cross sections analysis in PCA-REPLICA benchmark

The uncertainties in nuclear data give inaccurate values of reaction rates in shielding benchmarks. Consequently, the inclusion of the shielding benchmarks in the validation of the nuclear data would contribute to the production of general-purpose nuclear data evaluations. The validation of nuclear data goes through an essential step of sensitivity and uncertainty analysis. During this step, the evaluator determines which nuclear data necessitate adjustment. In this work, sensitivity and uncertainty analysis of reaction rates due to two primordial cross sections elastic and capture uncertainties of important isotopes in PCA-REPLICA benchmark are carried out. The reaction rates and their sensitivities are calculated by MCNP6.1 code. The weight window and energy cutoffs are two variance reduction techniques used in this calculation. The covariance matrices of the studied cross sections are processed by NJOY99 software. The sensitivities and uncertainties of the estimated reaction rates are calculated in four energy groups for three detectors 103Rh (n,n')103Rhm, 115In (n,n')115Inm and 32S (n,p)32P. The obtained results show that the elastic cross sections of 56Fe, 16O and 1H give large uncertainties on reaction rates, whereas the captures of these isotopes have small uncertainties on reaction rates. The analysis of the sensitivities and the uncertainties of the reaction rates due to elastic and capture cross sections of the 56Fe, 1H and 16O indicate that the elastic cross section of 56Fe needs improvement in the energy range 0.1 MeV-19.60 MeV and the elastic cross sections of 1H and 16O need adjustments in the energy range 1.35 MeV-19.60 MeV.