Capsule Integrity Report For Capsule Dry Storage Project

The cesium and strontium capsules stored in pools at the Waste Encapsulation and Storage Facility (WESF) will be moved to dry storage on the Hanford Site as an interim measure to reduce risk. The integrity of these capsules under the conditions of dry storage for a period of 50 years has been evaluated. Four deterioration mechanisms have been considered. These mechanisms include (1) swelling and/or pressurization of the capsules due to phase transformations of the salt; (2) deterioration of the welds; (3) corrosion of the capsules, and (4) mechanical failure of the capsule due to thermal aging. Corrosion of the capsules includes both external and internal corrosion of the capsules from the salts and is described in greater detail in WMP-16937, ''Corrosion Report for the Capsule Dry Storage Project''. Three accident scenarios that have the potential to challenge the integrity of the capsules are being considered for the dry storage module: (1) fire, (2) a blocked inlet or outlet from the dry storage module, and (3) a drop of the overpack. The drop scenario also includes an accident scenario where a stack of overpacks falls over. These accident scenarios are the best estimate of possible events as determined by an initial hazards analysis.