MECHANICAL EVALUATION OF A NATURAL UF6 TRANSPORT CONTAINER AT HIGH TEMPERATURE

International Alomic Energy Agency (IAEA) revised the transport regulation for natural Uranium hexafluoride (UF6 ) transportation taking into account chemical and radiological hazards in 1996. A supplementary fire test requirement (800\"C for 30 minutes) was imposed on the natural UF6 transport container. In 1996, Central Research Institute of Electric Power Industry (CRIEPI) and Nuclear Protection and Safety Institute (IPSN) terminated experimental joint research works with the aim to determine the thermal-physical behavior of UF6 in a transport container under realistic fue conditions and to use the experimental data to validate a thermal-hydraulic numerical model. Now, they have started a new experimental joint research as to the rupture test of the 48Y-cylinder which will be terminated at the end of 1998. The purpose of this study is to evaluate numerically the mechanical integrity of this cylinder in the IAFA fire test conditions. Firstly, pre-thermal-hydraulic numerical analysis of the 48Y -cylinder under the IAEA fue test condition was performed (Shirai, 1997). Nextly, the structural material model at high temperature for natural UF6 transport container was proposed based on the CRIEPI's material tests (Kosak.i, 1994) and applied to the ABAQUS computer code. According to the mechanical non-linear analysis results, it was found that it is necessary to evaluate the safety margin for the rupture of the 48Y -cylinder because considerable plastic and creep deformations are generated due to the temperature distribution of the cylinder and the inner pressure. This thermal-mechanical behavior of the container will be verified according to the rupture test results of the 48Y-cylinder until the end of 1998.