From Molecular Dynamics to Reactor Physics: Improvement on the Calculation of D2O Moderated Critical Systems with New Thermal Neutron Scattering Libraries

Abstract

Nuclear criticality calculations are needed both for the design of nuclear reactors and for the verification of nuclear criticality safety conditions on systems that include significant amounts of fissile materials. These calculations are based on neutron interaction data, which are distributed in evaluated nuclear data libraries.
To improve the evaluations of thermal scattering sub-libraries, we developed a set of thermal neutron scattering cross sections (scattering kernels) for deuterium and oxygen bound in heavy water in the ENDF-6 format. These new libraries are based on molecular dynamics simulations and recent experimental data, and result in an improvement of the calculation of single neutron scattering quantities. In this work, we show how the use of this new set of cross sections also improves the calculation of thermal critical systems moderated and/or reflected with heavy water, obtained from The International Criticality Safety Benchmark Evaluation Project (ICSBEP) handbook. The use of the new thermal scattering library for heavy water, combined with the ROSFOND-2010 evaluation of the cross sections for deuterium, results in an improvement of the C/E ratio in 48 out of 65 international benchmark cases calculated with the Monte Carlo code MCNP5, in comparison with the existing library based on the ENDF/B-VII.0 evaluation. Impacts on the ZED-2 international benchmarks from the recent edition of The International Reactor Physics Experiment Evaluation (IRPhE) Project handbook will be also discussed.