The influence of hydrogen pressure and reaction temperature on the initiation of uranium hydride sites

• Published in: Solid state ionics 2012-03, Vol.211, p.1-4
• Main Authors: Bazley, S.G., Petherbridge, J.R., Glascott, J.
• Format: Article
• Language: English
• Subjects: Abrasion; Abrasion resistance; Actinide alloys and compounds; Corrosion; Diffusion barriers; Diffusion layers; Gas–solid reactions; Hydrides; Hydrogen storage; Mathematical models; Metal hydrides; Uranium hydride
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2012.01.010

The influence of hydrogen pressure and reaction temperature on the initiation of uranium hydride sites has been determined in the ranges 60–1000mbar and 75-130°C, respectively. In order to study the influence of these reaction conditions independently of other possible experimental influences, it was necessary to develop a standard sample preparation (wet abrasion) and a drying pre-treatment (16h, 75°C, in-vacuo) methodology. It is shown that, under constant pressure and temperature conditions, the number of hydride sites varies as a power-like function of time. A power-like function may also be used to describe the relationship between the inverse of the time for the nth hydride site to appear (for n=1, 5, 10, 20 and 50) and the applied hydrogen pressure, with an exponent value of 1.3 and an associated activation energy of 57kJmol−1. These observations are broadly consistent with existing hydride initiation models in which the uranium surface oxide layer is considered to act as a barrier to hydrogen diffusion to the oxide–metal interface. ► Temperature and hydrogen pressure effects uranium hydride formation. ► A power relationship relates time to nucleation rate. ► A power relationship relates inverse time to hydrogen pressure. ► The apparent activation energy for uranium hydride formation has been determined. ► It is suggested that the oxide overlayer strongly influences hydride site nucleation.