Neutron cross section covariances from thermal energy to 20 MeV

Abstract

Abstract. We describe new method for energy-energy covariance calculation from the thermal energy up to 20 MeV. It is based on three powerful basic components: (i) Atlas of Neutron Resonances in the resonance region; (ii) the nuclear reaction model code EMPIRE in the unresolved resonance and fast neutron regions, and (iii) the Bayesian code KALMAN for correlations and error propagation. Examples for cross section uncertainties and correlations on 90 Zr and 193 Ir illustrate this approach in the resonance and fast neutron regions.

Modern Nuclear Data Evaluation with the TALYS Code System

“…There exist various mathematical rigorous methods for automatic parameter/cross section optimization, mostly based on Bayesian statistics. These methods include experimental data, with or without proper covariance matrices, directly in the optimization procedure, which yields both a parameter correlation matrix and a set of the optimized cross sections [91]. Alternatively, correlated sampling using multivariate Gaussian distributions could be performed, if one wishes to pursue Monte Carlo covariance methods.…”

New working methods for nuclear data evaluation: how to make a nuclear data library?

“…There exist various mathematical rigorous methods for automatic parameter/cross section optimization, mostly based on Bayesian statistics. These methods include experimental data, with or without proper covariance matrices, directly in the optimization procedure, which yields both a parameter correlation matrix and a set of the optimized cross sections [5]. Alternatively, correlated sampling using multivariate Gaussian distributions could be performed, if one wishes to pursue Monte Carlo covariance methods.…”