Impact of ENDF/B-VII.0 for AECL applications

This paper examines the impact of the new evaluated nuclear data library ENDF/B-VII.0 on selected reactor physics applications at AECL. The twin objectives are to provide feedback to the nuclear data community concerning the practical impact of their work and preliminary guidance to end-users. This work is based on comparison of the results of MCNP simulations with critical measurements involving both the ZED-2 zero power reactor and the MAPLE dedicated isotope production reactors at the Chalk River Laboratories. Significant improvement in the reactivity agreement with the measurements is obtained with ENDF/B-VII.0 for the specific ZED-2 measurements analysed; however, improvements associated with the thermal scattering law data for UO2 that had been observed initially were subsequently determined to be fortuitous, due to the inadvertent omission of the elastic neutron scattering component. Additionally, the net reactivity impact of major changes to the 90Zr and 91Zr capture cross sections with ENDF/B-VII.0 is examined in the MAPLE reactor context and found to be modest due primarily to the offsetting effects of the specific nuclides involved. (authors)