Cross Code Verification of a Thermal Stress Analysis of a Thin Walled RAM Transport Package during and after a Regulatory Pool Fire

Finite Element Analysis (FEA) is an effective tool for assessing packages used to transport Radioactive Materials (RAM) in normal operation and in extreme, hypothetical accident conditions. RAM transport packages must satisfy the requirements of the IAEA Regulations by demonstrating their performance in a series of tests including a 9m drop onto an unyielding target and a subsequent 30 minute pool fire with a flame temperature of 800°C. Sufficient performance of a RAM transport package in an accident is determined by its ability to maintain a containment boundary in any impact or fire scenario and to withstand the cumulative effects of an impact followed by a fire.In this paper a thin walled package, consisting of three concentric shells, has been assessed to determine which shell is most likely to fail as a result of a thermal accident. The package utilises a polymeric neutron shielding material between the concentric shells which may exceed its degradation temperature during the fire and begin to off-gas, thereby generating pressure. The analysis considers the combined effects of thermal expansion and internal pressure acting on the inner and outer shell during the fire transient and a subsequent cool down period.The problem has been solved in two analysis codes, Abaqus and LS DYNA to cross-verify the results. This paper discusses the merits and limitations of both Finite Element Codes when used for solving sequentially-coupled thermal stress problems.