Pressure Build-Up Inside Packages Containing Wet Intermediate Level Radioactive Waste due to Thermal Loads

Abstract

Over the last years several transport approval procedures were finished for ductile cast iron containers containing wet intermediate level waste. BAM was involved in the assessment of mechanical and thermal aspects, activity release and material and component behavior regarding fulfillment of the regulatory requirements. The radioactive contents of these package designs which were not dried, only drained, consist of saturated ion exchange resin and a small amount of free water. Regarding wet contents, the most interesting point, however, is the pressure build-up inside the package due to vaporization. This could be caused by radiolysis of the liquid and must be taken into account for the storage period. The paper deals primarily with the pressure build-up inside the package caused by the regulatory thermal test (30 min at 800°C) as part of the cumulative test scenario under accident conditions of transport. The pressure build-up is estimated by calculation in a very conservative way regarding conduction and heat radiation. To get trustworthy results without an exact specification of the content, physical fire tests should be conducted. This paper will result in the strong advice, that contents should be dried to ensure a positive outcome of the safety assessment.