Numerical sensitivity analysis of rector neutron spectrum

Abstract

The uncertainty data of a neutron spectrum can be completely described by the corresponding covariance matrix. The main diagonal of such covariance matrix consist of the variances of the energy group flux values, and the off-diagonal elements give the cross-covariance between these values. The major step in evaluating the covariance matrix of a calculated neutron spectrum is the derivation of the sensitivity matrix. The covariance matrix can be evaluated by performing a simple multiplication of the sensitivity matrix and a covariance matrix consisting of basic cross-section covariance data taken from literature. Numerical sensitivity analysis usually made whenever there is a lack of analytical tools. In the frame of this work, a numerical procedure based on the sensitivity analysis theory have been developed to estimate this information. In this procedure, results of several neutron transport calculations are used to derive numerically the sensitivity matrix of the calculated neutron spectrum.

The uncertainty data of a neutron spectrum can be completely described by the corresponding covariance matrix. The main diagonal of such covariance matrix consist of the variances of the energy group flux values, and the off-diagonal elements give the cross-covariance between these values. The major step in evaluating the covariance matrix of a calculated neutron spectrum is the derivation of the sensitivity matrix. The covariance matrix can be evaluated by performing a simple multiplication of the sensitivity matrix and a covariance matrix consisting of basic cross-section covariance data taken from literature. Numerical sensitivity analysis usually made whenever there is a lack of analytical tools. In the frame of this work, a numerical procedure based on the sensitivity analysis theory have been developed to estimate this information. In this procedure, results of several neutron transport calculations are used to derive numerically the sensitivity matrix of the calculated neutron spectrum.