NUMERICAL AND EXPERIMENTAL EVALUATIONS OF THE EFFECTS OF A PACKAGING SYSTEM FREE DROP

A safety management of the radioactive wastes unavoidably involves the pre-treatment, the treatment, conditioning, storage and disposal of all categories of radioactive wastes, including transportation activities. An essential component for any safe shipment is thus a robust safe and reliable system (or “cask”) constituted by a massive sealed steel and concrete canisters to provide both structural strength and radiation shielding. The casks or packaging systems, used for the transportation of nuclear materials, especially the spent fuel elements (SPE), are designed according to rigorous acceptance requirements, such as the ones provided by the International Atomic Energy Agency (IAEA), in order to provide protection to human being and environment against radiation exposure and contamination particularly in a reference accident scenario that may include, as it is well known, several types of test conditions as drop, puncture, fire and submersion tests. The present study deals with the evaluation of the structural response and performance in free drop test conditions of a new Italian packaging system that should be used for the transportation of low and intermediate level radioactive wastes. To the purpose the carried out numerical and experimental analyses are presented and discussed. The experimental tests were performed at the University of Pisa, by dropping a full scale solidified waste packages (with simulated inert content) into a flat unyielding surface in order to demonstrate and assure the structural integrity as well as to check the induced damaging effects, in the conditions foreseen in the previously mentioned IAEA recommendations. To simulate and determine the progressive damage, during the impact conditions, numerical models of both the considered cask and target surface have been set up and implemented in a rather refined way, taking into account suitable material properties and constitutive laws. The comparison between the obtained experimental and numerical results highlighted that, although rather severe local deformations, the whole packaging system was capable to withstand the impulsive dynamic loading generated during the drop test without unacceptable loss of safety feature and that the numerical approach is able to reproduce with high reliability the test situations.