Plutonium Air Transfortable Package Development Using Metallic Filaments and Composite Materials

A new design concept for plutonium air transport packagings has been developed by the Transportation Systems Department and modeled by the Engineering Mechanics and Material Modeling Department at Sandia National Laboratories (SNL). The new concept resulted from an in-depth review (Allen et al., 1989) of existing package design philosophies and limitations. This review indicated a need for a new package which could survive combinations of impact, fire, and puncture environments, and which could be scaled up or down to meet a wide range of requirements for various contents and regulations. This new design concept uses a very robust primary containment vessel with elastomeric seals for protection and confinement of an inner containment vessel with contents. An overpack consisting of multiple layers of plastically-deformable metallic wire mesh and high-tensile strength materials is placed around the containment vessels to provide energy absorption for the primary containment vessel as well as thermal protection. The use of intermittent layers with high-tensile strength results in a limiter which remains in place during accidental impact events and can be relied upon to provide subsequent puncture and fire protection. In addition, an outer shell around the energy absorbing material is provided for handling and weather protection. To validate the concept, numerous scoping tests were performed on material samples, wall sections, and partially modeled prototypes. To evaluate various design features, finite element analyses were performed on the package. The finite element analysis required the development of a new constitutive theory for layered composite materials. The effects of net;lecting the anisotropic tensile behavior were investigated with a series of dynamic finite element analyses. The model was implemented in both static and dynamic finite element codes and a number of steps were completed to benchmark the model. Uniaxial compression and tension experiments were performed on various candidate materials to obtain appropriate material properties for the model. Scale model packages subjected to side and end impacts were analyzed. Prototype scale model packages were fabricated and subjected to 129 m/s side impact and 200m/send impact tests, respectively. Test results indicated that the overpack would remain intact throughout a worst case accident, and that structural loads on the containment vessel could be limited to assure integrity of the containment vessel.