Mechanical sensitivity considerations for finite element analysis supporting Type A package licensing

Fissile shipping packages are fabricated from materials governed by recognized international standards to ensure that consistent, traceable components constitute the package design and fabrication. These standards typically identify material property minima or range values enabling the designer to fully assess the material for design capability and expected performance. However, construction materials are rarely, if ever, fabricated purposely to specification minimum. In addition to stated mechanical properties, materials exhibit temperature dependent characteristics which may impact the material behavior when subject to Normal and Accident transport conditions. Type A fissile shipping packages are governed by SSR-6 as well as 10CFR71 ensuring structural integrity is maintained when subject to the transport conditions. Since regulatory test articles are not fabricated to the most limiting material properties, shipping package designers frequently utilize dynamic, large strain capable software to evaluate the package's structural robustness supporting a license application. Package designers must identify which package safety components are not at a limiting condition and provide justification that the package's structural robustness is not compromised. Justification may be demonstrated by testing, analysis, or both. Finite Element Analysis (FEA) software assessed the Westinghouse Traveller fresh fuel shipping package for recent licensing efforts when considering limiting material conditions. The results of the FEA demonstrate that the initial Traveller package robust design provides adequate margin against manufacturing tolerances, temperature-dependent material property variability, and a combination thereof. (author)