The influence of external stress/strain on the uranium-hydrogen reaction

Hydriding experiments performed on bent uranium samples indicated that increasing the applied tensile stress shortens the nucleation and growth periods of the hydrides and facilitates the formation of hydride growth centers (GCs). The results enable the distinction between the influence of the reversible stress-induced elastic component and the irreversible plastic one. It was concluded that the elastic contribution is most significant in the very initial nucleation and (limited) growth of the “small family” hydride spots, that occur beneath the intact oxidation overlayer. On the other hand, the plastic deformation, which induces microstructural changes in the metal, controls the mechanical rupture of that oxide thin layer, thereby facilitating the conversion of the “small family” into GCs. The combined effects of these two contributions control the experimental nucleation and growth periods observed in the overall kinetics of the hydrogen-metal reaction.