Numerical investigation of Al-foam shock absorber for transportation cask

Presently, lead filled steel casks are used worldwide for transportation of radioactive materials as Type B package. The disadvantage of lead as shielding material is because of having low boiling point and high thermal expansion, which causes problem during fire and melted lead come out from the containment breach. In recent years research on thick walled metallic cask for transportation is under progress. Hence, preliminary design and development of Ductile Cast Iron (DCI) cask is carried out for the next generation of transport cask. Furthermore, in lead filled cask, lead also acts as impact absorber and absorbs 60-70% impact energy. However, in DCI cask, most of the impact energy is transferred to the containment. Therefore, shock absorber is essential in these casks to maintain the structural integrity of the containment to meet the regulatory requirements. The regulatory standards require that the containment design shall be certified for transportation shall have to maintain structural integrity under hypothetical accident conditions such as 9 m drop on unyielding target. Numerical analysis of casks with shock absorbers during accident is highly non-linear due to impact, rebound, material and geometrical non-linearity and has convergence issue during solution procedure. The possibility of using uniform porous Al-foam shock absorber is investigated in detail. There is no reported work available in the literature incorporating impact, rebound, material and geometrical non-linearity for DCI cask with impact absorber. Finite Element based numerical analysis has been carried out to observe the effectiveness of shock absorber during 9 m drop. Various parameters like impact stress, strain, kinetic energy, and absorbed energy of Al foam during impact have been analyzed and discussed in detail. It is found from the numerical analysis that Al-Foam based shock absorber are well suitable for heavy cask.