A Proposal for an International Brittle Fracture Acceptance Criterion for Nuclear Material Transport Cask Applications*

The use, or proposed usc, of materials other than stainless steel for structural components of transportation casks is becoming increasingly common. Examples of structural cask components which may be manufactured from alternate materials include the containment boundary as well as the internal spent fuel basket. Specific alternate materials include low alloy ferritic steels. titanium, depleted uranium, aluminum, borated stainless steel and ductile cast iron (DCI). The technical issue which separates these alternate materials from the austenitic stainless steels is that they can, under certain environmental and mechanical loading conditions in combination with a flaw, fail in a lowenergy fracture mode at stresses below yield level. Cask designers and regulators are responsible for assuring that these cask components are designed such that low-energy fracture is precluded.