Solution of hydrogen in accident tolerant fuel candidate material: U3Si2

Hydrogen uptake and accommodation into U3Si2, a candidate accident-tolerant fuel system, has been modelled on the atomic scale using the density functional theory. The solution energy of multiple H atoms is computed, reaching a stoichiometry of U3Si2H2 which has been experimentally observed in previous work (reported as U3Si2H1.8). The absorption of hydrogen is found to be favourable up to U3Si2H2 and the associated volume change is computed, closely matching experimental data. Entropic effects are considered to assess the dissociation temperature of H2, estimated to be at ∼800 K – again in good agreement with the experimentally observed transition temperature.