[2E14-18] High-temperature Gas-cooled Reactor, Fundamental Property

[2E16] Evaluation of inelastic neutron scattering of (Ca,Sr)F₂ with machine-learning molecular dynamics

*Hiroki Nakamura¹, Masahiko Machida¹, Masashi Watanabe¹, Masato Kato¹ (1. JAEA)

Keywords:CaF2, SrF2, Bredig transition, Inelastic neutron scattering, Machine-Learning Molecular Dynamics

It is difficult to measure the thermal properties of nuclear fuel materials, such as MOX fuel materials, at high temperature just below their melting points. Solid solution of calcium fluoride and strontium fluoride, (Ca,Sr)F₂, is sometimes employed as alternative MOX fuel materials. In this paper, we evaluate the (Ca,Sr)F₂ dynamic structure factor measured by inelastic neutron scattering using machine-learning molecular dynamics trained by first-principles calculations. We investigate the behavior of the dynamic structure factor at the Bredig transition temperature, at which heat capacity rapidly increases. We also discuss application of the present method to MOX fuel materials.