Abstract:
The Heavy Element Facility houses underground vaults for long-term storage of nuclear materials, each utilizing stainless steel containers supported in racks. While hazard and accident assessments considered the static stability of these containers, this study applies finite element analysis to evaluate their structural integrity under rare, short-duration dynamic events. Specifically, the analyses simulate accidental free drops that could result from a combination of seismic excitation and crane operations, focusing on the uppermost container in a storage rack. Using DYNA3D finite element modeling, two container models were developed: one representing a lumped mass at the flange and another capturing internal dynamic interaction of the capsule and juice can within the container. Dynamic simulations at various drop angles and heights were performed to assess stress propagation, deformation, and containment capacity, with a focus on the O-ring assembly, flange, and lid as critical components for maintaining an airtight seal. Results showed that while the containers are structurally robust, certain drop conditions could compromise the hermetic seal due to flange-lid deformation and reduced O-ring compression. The juice can was also shown to deform under impact, though it is not relied upon for containment. These findings suggest that in the unlikely event of a container drop, secondary containment could be breached, highlighting the need for simple engineering modifications such as shelf redesigns or increased flange strength. The study demonstrates the central role of finite element analysis in predicting failure modes, validating safety margins, and guiding engineering improvements for nuclear material storage systems.
