Stability evaluation methodology of the dual purpose metal cask attached to a transfer air pallet during long-period seismic motions

After the nuclear accident occurred on March 11, 2011, strict safety technical requirements on nuclear facilities were issued by Japanese governments to verify countermeasures to assure the safety functions of the facilities even if under severe accident conditions. When the air pallet system is adopted for transfer within the metal cask storage facility site, the metal cask attached to a transfer air pallet may be operated vertically without tie-down system. In order to prevent the damage of the safety functions of the metal cask, it is important to assess the stability of the metal cask attached to a t ransfer air pallet subjected to strong long-period seismic motions. Considering the similarity law referring the configuration of the metal cask attached to a pallet, 2/5 scale metal cask and transfer pallet models were fabricated and applied for seismic tests on the concrete pad to evaluate its stability under the influence of long-period earthquake motions. Moreover, a rational methodology based on the energy spectrum was proposed and verified as a practical tool for evaluating the occurrence of the overturning when the vertically standing cask without tie-down system.