Published January 2012
NDS Staff Publication
Covariances of Evaluated Nuclear Cross Section Data for 232Th, 180,182,183,184,186W and 55Mn
- 1. Nuclear Data Section, IAEA
Description
The EMPIRE code system is a versatile package for nuclear model calculations that is often used
for nuclear data evaluation. Its capabilities include random sampling of model parameters, which
can be utilised to generate a full covariance matrix of all scattering cross sections, including crossreaction
correlations. The EMPIRE system was used to prepare the prior covariance matrices of
reaction cross sections of 232Th, 180,182,183,184,186W and 55Mn nuclei for incident neutron energies up
to 60 MeV. The obtained modelling prior was fed to the GANDR system, which is a package for a
global assessment of nuclear data, based on the Generalised Least-Squares method. By introducing
experimental data from the EXFOR database into GANDR, the constrained covariance matrices
and cross section adjustment functions were obtained. Applying the correction functions on the cross
sections and formatting the covariance matrices, the final evaluations in ENDF-6 format including
covariances were derived. In the resonance energy range, separate analyses were performed to
determine the resonance parameters with their respective covariances. The data files thus obtained
were then subjected to detailed testing and validation. Described evaluations with covariances of
232Th, 180,182,183,184,186W and 55Mn nuclei are included into the ENDF/B-VII.1 library release.