Internal environment of AL-R8 storage containers

Nuclear pits are currently stored for short time periods (although the time period can extend up to 5 years or longer in some cases) in unsealed AL-R8 containers at the Pantex Plant in Amarillo, TX. The AL-R8 consists of a steel drum lined with Celotex® insulation that serves to mediate thermal fluctuations, suppress flammability, and provide shock mitigation. Previous studies have identified high chloride and sulfate content in Celotex® and questioned the use of this material in pit storage operations. In addition, the storage facilities for AL-R8 containers are not maintained at a constant temperature or relative humidity, and it is unclear what effect varying environmental conditions will have on the internal environment of the AL-R8 containers. Our initial studies indicate that there is a significant lag (several hours) between an elevated external temperature and the air temperature inside the AL-R8, but the relative humidity inside the AL-R8 also increases rapidly during this lag time. However, preliminary experiments indicate that an increased relative humidity outside the AL-R8 has little effect on the interior environment. The presentation will present and discuss the results from more detailed studies of the AL-R8 storage conditions. Our current studies utilize an internal heat source, multiple air temperature and relative humidity dataloggers, and a series of thermocouples to monitor the surface temperature at various points in the container. The instrumented AL-R8 container has been subjected to a range of external temperature and relative humidity conditions including a diurnal variation cycle that attempts to mimic actual storage conditions. We will present the results from these studies, discuss any implications for pit storage operations, and suggest future directions for the storage program.