The influence of vacuum annealing on the uranium–hydrogen reaction

• Apparent activation energies of the U–H2 reaction.
• Enhanced H2 reactivity occurs with vacuum annealed uranium.
• Transition from nucleation to growth mechanisms is demonstrated.
• Elevated nucleation kinetics affords the enhanced H2 reactivity observed.

The constant pressure hydriding kinetics of uranium have been measured as a function of temperature for as-polished and vacuum annealed uranium between 65 °C and 385 °C. Enhanced hydrogen reactivity was observed for vacuum annealed uranium between 65 °C and 120 °C and is the result of elevated nucleation kinetics promoting steady state kinetics.