Covariances of Neutron Fluxes and Cross Sections in Group Structure Variation

The propagation of neutron flux and cross-section covariances through a group structure variation is investigated and discussed. Explicitly taking into account the initial covariances between different cross sections and between cross sections and fluxes, expressions for the covariance matrix of modified group structure, i.e., a new group structure with different energy limits, are obtained. A numerical example illustrating the whole procedure is reported.