Microstructural Characterization of Subsurface Corrosion Features in Flow-Formed Plutonium-Bearing Nested Storage Canisters (C2026-00416)

Emmanuel Perez, Maxwell Alderman, Roderick Fuentes

The Integrated Surveillance Program, under the Department of Energy, is responsible for the periodic surveillance of storage containers containing plutonium-bearing materials. The container-package consist of a stainless-steel three-layered structure with a convenience can that confines the material, and seal-welded inner and outer cans designed to isolate the materials for up to 50 years with minimal surveillance.
Monitoring is carried by random and engineering-judgment selections and destructive examinations. Corrosion in the convenience- and inner-cans has been observed in some packages. The corroding environment is believed to be the result of chloride salts and water impurities in the stored materials. Because the inner-can is the first isolation layer, corrosion features here are undergoing detailed characterization to determine if risk of a breach is probable.
The canisters were manufactured via flow-forming processes. Due to significant mechanical deformation of the stainless-steel, the cans exhibit intricate microstructures with likely complex stress-states that can affect the corrosion processes. Herein, microstructural characterization of the cans by Scanning-Electron-Microscopy and Electron-backscatter-diffraction is utilized to introduce the subsurface microstructure of the cans. Examination by Focused-Ion-Beam-Tomography is presented to reveal subsurface corrosion features and to attempt to correlate microstructural features to the propagation of subsurface corrosion in the flow-formed material.