Thermogravimetric analysis on alkaline earth hydrides in St Andrews has revealed a remarkably fast exchange of deuterium and hydrogen by alkaline earth hydrides at relatively low temperatures. This exchange confirms the fast bulk transport of hydrogen in these hydrides, but also shows rapid surface exchange with the atmosphere. The isotopic exchange is relevant not only from a hydrogen storage perspective, but also shows the materials¿ catalytic potential in, for instance, hydrogenation reactions.We propose to perform two sets of experiments on AeD2 (Ae = Ca, Sr, Ba) to probe D diffusion and exchange properties. The structure of the deuterides will be investigated as a function of temperature under flowing 5%D2 and 5%H2 using the concentration cell as proposed here. Parallel thermogravimetric analysis will be carried out at the Hydrogen Research facility at ISIS and at St Andrews.