REVISION OF THE ASME SECTION III, DIVISION 3 CODE FOR PUNCTURE ANALYSIS

The current version of the ASME Boiler and Pressure Vessel Section III, Division 3 Code calls for design to resist puncture of lead shielded casks by use of Nelm's equation. This approach does not provide any guidance to the designer for other types of casks or for design of the inner shell in a multi-shell design. A recent ASME Code Case (N-626) provides guidance for design of the containment boundary based upon inelastic analysis. Sandia has performed a series of tests and analyses to examine the puncture event to determine the margin of safety for any proposed new design methods. This paper will examine the results of the Sandia test and analysis series, report on ongoing activities with respect to the puncture event within the ASME NUPACK committee, and propose a broadly applicable design methodology to be included in the Code. The purpose for changing the Code is so it provides a robust methodology for design of all cask types to resist the puncture event while maintaining current factors of safety. In general, the Code is specifically applicable to the containment boundary of these casks. However, for casks with multiple layers in their wall, the outer layer may also be important to safety, and cask designers should be able to look to the Code for guidance. Therefore, it is important to have design acceptance criteria that can be used for both the inner and outer shells of this type of cask. The work at Sandia has demonstrated that finite element analysis tools are capable of accurately predicting the response of packages to puncture events. The analyses have also shown that prediction of ductile tearing is most accurate when based on an accumulation of ductile damage failure criterion. Current ASME Code philosophy is more aligned with a stress-based acceptance criterion. This paper will discuss the validity and utility of using a stress-based acceptance criterion for design to resist puncture.