Modeling of diffusion of plutonium in other metals and of gaseous species in plutonium-based systems. 1998 annual progress report

'The problem being addressed is to establish standards for storage conditions for containers (e.g. stainless steel containers) meant to hold nuclear waste for long periods of time, e.g. fifty years, such as to ensure the integrity of the containers without being excessively conservative, i.e., being unnecessarily costly. Allowable storage temperature is an important parameter for the standards. Diffusion processes are central to certain processes that initiate corrosion of the containers or that lead to the release of gases increasing pressure that can rupture the container. The scientific goals of this project are: (1) to predict diffusion constants on an ab initio basis, i.e. diffusion distances in specified time at specified temperature, for atomic species from plutonium-based waste materials into storage container materials such as stainless steel or vice versa, (2) to predict the time development at specified temperature of complex diffusion processes in plutonium-based oxide type waste materials in the presence of water vapor such that gases may be released within a container. This predictive ability will help to provide information relevant to setting standards for waste container vessels and storage conditions. This project was initiated on September 15, 1997, so that this summary reports progress after about 2/3 of the first year of a three-year project.