Thermal neutron scattering measurements and modeling of yttrium-hydrides for high temperature moderator applications

Thermal neutron scattering measurements of yttrium hydride from 5 to 1,200 K were conducted to determine the change in inelastic scattering as a function of temperature and to probe for anharmonic effects. Additionally, measurements on samples of YHx from x = 1.62 to 1.90 were done to determine the effects of varying hydrogen concentration on the inelastic spectra. Changes in temperature affected the inelastic spectra in unanticipated ways, indicating that there are anharmonic effects, whereas hydrogen concentration did not significantly affect the inelastic spectra. These measurements were compared against the ENDF/B-VIII.0 thermal scattering files of YH2, as well as new thermal scattering files created by using the stochastic temperature-dependent effective potential (s-TDEP). Both libraries were found to be in good agreement with the experimental data at lower temperatures. At higher temperatures, the sTDEP method is better at predicting the experimentally observed softening of phonon modes in acoustic and optical regions. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study found that changes in temperature affect the inelastic spectra, indicating the presence of anharmonic effects, while hydrogen concentration has minimal impact on the inelastic spectra. Experimental data was in good agreement with predictions by the new method sTDEP at higher temperatures.