Impact of crystallite size on the performance of a beryllium reflector

TL;DR

This paper investigates how the size of crystallites in beryllium reflectors affects neutron scattering and system performance, highlighting the importance of incorporating crystallite size effects into simulation models for accurate design.

Contribution

It introduces corrected cross-section libraries accounting for crystallite size effects in beryllium, improving the accuracy of neutron system simulations.

Findings

Crystallite size influences neutron scattering in beryllium.

Inclusion of size effects improves reflector performance predictions.

Preliminary results show noticeable differences in simulations.

Abstract

Beryllium reflectors are used at spallation neutron sources in order to enhance the low-energy flux of neutrons emanating from the surface of a cold and thermal moderator. The design of such a moderator/reflector system is typically carried out using detailed Monte-Carlo simulations, where the beryllium reflector is assumed to behave as a poly-crystalline material. In reality, however, inhomogeneities in the beryllium could lead to discrepancies between the performance of the actual system when compared to the modeled system. The dependence of the total cross section in particular on crystallite size, in the Bragg scattering region, could influence the reflector performance, and if such effect is significant, it should be taken into account in the design of the moderator/reflector system. In this paper, we report on the preliminary results of using cross-section libraries, which include corrections for the crystallite size effect, in spallation source neutronics calculations.