Summary of Plutonium Oxide and Metal Storage Package Failures

This article compiles available documented information on failures of containers used to store plutonium-bearing oxide and metal materials within the context of the U.S. Department of Energy (DOE) stabilization, packaging, and storage standard DOE-STD-3013. Relevant information was obtained from published DOE-wide plutonium storage safety evaluations, workshops, technical reports, scientific journal publications, and direct discussion with many subject matter experts. This article focuses on the past two to three decades of plutonium oxide and metal storage, during which package failures were reasonably well-documented. Storage of residues and wastes is not covered in this study. Based on the documented information examined, this report identifies two dominant modes for plutonium oxide and metal storage package failure: • Metal oxidation due to non-airtight packages • Gas pressurization from radiolytic and thermal degradation of inadequately stabilized materials and organic constituents Four key considerations for safe storage of oxide and metal are identified: • Adequacy of the calcination process • Container resistance to pressure • Container sealing requirements • Container resistance to corrosion and radiation The evaluation shows that rational explanations exist for all documented failures and that the associated conditions are well addressed by the requirements of DOE-STD-3013, for materials applicable to this standard. Since vulnerability studies were conducted in 1994 and appropriate corrective actions were taken, only one significant DOE actinide storage container failure for plutonium oxide or metal is known, and that resulted from an inadequate closure weld in a singly contained package.