Demonstrative Rupture Test and Safety Evaluation of a Natural UF_6 Transport Cylinder at High Temperature

摘要

If a natural uranium hexafluoride (UF_6) transport container is involved in a fire test condition as described in the new requirements from the International Atomic Energy Agency (IAEA), packaged UF_6 can easily be transformed from solid phase to liquid or gas phase at a comparatively low temperature, and can cause an inner pressure increase. Therefore, it is very important to evaluate the thermal-mechanical characteristics of UF_6 transport containers under realistic fire conditions. Rupture tests with the 48Y-cylinders were performed in the joint research works (PEECHEURE Program) between Central Research Institute of Electric Power Industry (CRIEPI, Japan) and Nuclear Protection and Safety Institute (IPSN, France). This type of cylinder seems to be deformed and ruptured near the stiffener ring due to creep deformation. A series of material tests on small-scale specimens of the container material were performed to propose creep deformation formula and a rupture criterion. To assess the rupture possibility of the container, this proposed nonlinear creep material model was applied to the ABAQUS code and the numerical analysis was performed and compared with the rupture test results. Finally, according to the thermal-mechanical analysis for 48Y-clinders with the Japanese heat protection system, it can be concluded that this natural UF_6 transport system has enough safety margin for the new IAEA fire test requirement.