Demonstration of the avoidance of brittle fracture of a radioactive material transport package during an impact event

Abstract

The stress-based assessment described in BS7910:2019 for the demonstration of avoidance of fracture initiation has been applied to a radioactive material transport package. The transport package was designed and manufactured in the early 1990s, predating modern regulatory requirements that are more prescriptive to satisfy the avoidance of brittle fracture. The package design can be usefully re-purposed for the transport of low/intermediate level waste - such as that produced in prototype fission reactors. Current regulations may require demonstration of the avoidance of brittle fracture for this type of package at -40°C in a fault condition -which, for this package, is considered as an impact from a 1.2m drop height. This paper presents an overview of the demonstration of the package, explaining the process of identifying transient stresses throughout the package and then focusses on treatment of high stresses in the base of the package. Stress classification into primary and secondary stresses is discussed. It is demonstrated that such stresses are permissible by extrapolating from solutions in BS7910:2019 Annex N using cracked body models and taking advantage of low constraint conditions at the crack tip.