Low temperature vacuum drying of spent nuclear fuels and fuel debris

Throughout the worldwide nuclear complex, spent nuclear fuels and fuel debris destined for repository disposition will be prepared for dry storage. The preparation may involve fuel repackaging coupled with some degree of fuel drying for the materials stored underwater. The governing drying parameters are the heat inputs/losses, the extent of dryness required, the spent fuel containment configuration, and the type of fuel material (e.g., oxide, metal, hydride, alloy, carbide, epoxied, debris). The Idaho National Engineering and Environmental Laboratory (INEEL) has previously operated high temperature vacuum drying systems and placed into interim dry storage many types of spent nuclear fuel. Most recently, due to safety and environmental concerns, epoxied spent nuclear fuel and debris have necessitated the use of low temperature vacuum drying systems. This paper describes the low temperature fuel process used to dry INEEL spent nuclear fuels, the methods developed to monitor the extent of dryness, and lessons learned for low temperature vacuum drying.