NUMERICAL STUDY OF THE MECHANICAL BEHAVIOUR OF TYPE B RADIOACTIVE MATERIAL PACKAGES IMPACTING REAL TARGETS

This paper presents (1) numerical drop impact simulations of type B radioactive material packages, (2) a comparison between the package damages caused by the 9m free drop onto a regulatory unyielding target and those caused by impacts on various targets, and (3) a mathematical model to evaluate the global mechanical behaviour of packages under impacts onto real targets. Detailed finite element models of two packages (TN12 for the transport of spent fuel and FS47 for the transport of plutonium dioxyde powder) and of real targets have been developed to evaluate the structural integrity of packages during the drop impact accidents. Then, several mechanical impact simulations using the state-of-the-art numerical methods have been performed. The structural analyses were conducted by three dimensional analysis models using highly non-linear structural dynamic codes (DYNA3D, ABAQUS, and PAM-CRASH). The drop impact simulations included: • impact of typical spent fuel shipping cask on various types of soils (clay, sand, and rock); • impact of the TN12 and the FS47 on various metallic targets likely to be encountered during transport or handling; • impact of the TN12 and the FS47 on a reinforced concrete structure; • impact of packages on each other (TN12-TN12, FS47-FS47). For each impact situation, several configurations, depending on the package orientation, the impact point on the target, and the drop height, have been simulated. These simulations point out the shock energy repartition between the package-target components, and highlight the high level energy absorption by the rack of the FS47, the frame of the TN12, and also by the target structure. Results show that for the two packages studied, the simulated situations of handling accidents appear less severe than the regulatory drop tests.