Explain the temperature dependence of hydrogen retention at helium cavities

Establish an atomistic explanation for the strong temperature dependence of hydrogen retention near helium cavities that is not fully captured by current atomistic models.

Background

Hydrogen trapping at helium-cavity interfaces is reported to be thermally unstable at elevated temperatures, with molecular-dynamics calculations predicting detrapping above approximately 127 °C and experiments indicating trapping energies corresponding to detrapping temperatures of roughly 227–327 °C. Although these results provide evidence for temperature-dependent retention, the available atomistic models do not yet account fully for the observed behavior.

The unresolved issue is important because hydrogen and its isotopes can remain localized near irradiation-induced helium cavities in fusion structural materials, directly affecting tritium inventory and fuel-cycle performance. A satisfactory atomistic explanation would need to reconcile the calculated detrapping behavior with experimental retention observations at elevated temperatures.