Results of the Sandia National Laboratories MOSAIK Cask Drop Test Program·

There has been a significant international effort over the past ten years to qualify structural materials for construction of radioactive material (RAM) transportation casks. As total life cycle cost analyses argue the necessity for more efficient casks, new candidate structural materials are evaluated relative to the historically accepted austenitic stainless steels. New candidate cask containment materials include ferritic steels, ductile iron, depleted uranium, and titanium. Another material, borated stainless steel is being considered for structural cask internals because of its neutron absorption properties. The mechanical performance of the borated stainless steels is a function of the boron content and metallurgical processing conditions. A separate paper in this symposium (Stephens et al. 1992) deals with the properties of a range of borated stainless steels. A major technical issue involved with the qualification of all these candidate materials is that they may, under certain combinations of mechanical and environmental loading, fail in a brittle fashion. Such a failure would of course not be acceptable for a RAM transport cask involved in an accident. The cask designer must assure cask owners, regulators as well as the general public that the cask will not undergo brittle fracture for all regulatory loading conditions. Qualification of ferritic metals, and in particular ductile iron, has progressed on a number of fronts. Standards development and analyses and testing programs have been pursued through a number of international organizations. Two companion papers are also being presented at PATRAM '92; the first paper (Sorenson et al. 1992) deals with developing a brittle fracture evaluation criterion through the lAEA and the second paper (Salzbrenner et al. 1992) describes the materials characterization program for the MOSAIK casks. This paper summarizes the drop tests that were conducted using the MOSAIK casks to verify the fracture mechanics cask design approach and to demonstrate that ductile iron could be subjected to severe loading conditions without failing in a brittle manner.