Dynamic Finite Element Analysis of Drum-Type Shipping Packages for Radioactive Materials

Abstract

The US Department of Energy (DOE) often uses Type AF and Type B drum-type packages for shipment of radioactive materials (RAM), both of which shall be designed and certified to meet the regulatory requirements specified in 10 CFR 71, to ensure safety, public health and protection of environment. In particular for the hypothetical accident conditions (HAC) prescribed in 10 CFR 71.73, RAM packages are subjected to sequential tests of 30-ft drop, crush, puncture, engulfing fire, and water immersions. Packages shall maintain structural integrity of containment, radiation shielding, and criticality control following these HAC tests. The structural evaluation (i.e., drop, crush, and puncture) of packages should address different combinations of test conditions, such as drop orientations, sequence, temperature and payload during the drop, crush and puncture tests. The combinations to be considered are those which would produce most damage to the package, challenge the most vulnerable packaging components, and cause the most cumulative damages. The evaluation of the most damage should also consider the effects of fire and water immersions following the structural tests. In this paper, the structural evaluation details of two drum-type packages, Model 9979 Type AF and Model ES-3100 Type B(U)F, are discussed. The design and performance of these packages were evaluated by physical testing of full-size prototype units. However, it is not practical to account for the worst test conditions and sequence in physical testing. Therefore, confirmatory finite element analyses have been performed to determine whether the cumulative damage resulting from the worst test sequence and conditions is acceptable. It was found for the 9979 package, the corner drop followed by corner crush causes most damage, and most unfavorably challenges its split-ring closures; for the ES-3100 package, the containment vessel (CV) experiences maximum strain following the sequence of bottom-to-lid slapdown and side crush. Although a lower temperature does not compromise their structural performance, the ES-3100 CV does experience slightly more strain because the impact limiter imparts more impact load because of its higher stiffness at lower temperature. In summary, the confirmatory analysis results show that the structural performance of the packages meets the regulatory requirements.