Failure of spent nuclear fuel canister mock-ups at isostatic pressure

This paper describes isostatic pressure tests of two large-scale mock-ups of Swedish copper/ductile cast iron canisters for geological disposal of spent nuclear fuel and the associated finite element analysis and micro-structural analysis. The key objective of the study was to demonstrate the safety margins against the very high pressure loads that could occur in a future ice age (44 MPa) and to determine the associated failure mode. The mock-ups were loaded to 130 and 139 MPa, respectively, in the tests. The dominant failure mode was plastic collapse in combination with some ductile tearing of manufacturing flaws. The observed deformations and the final failure loads are in good agreement with the finite element calculations. The post-test micro-structural analysis by radiography, ultra-sound techniques and fractography showed that the manufacturing defects in regions with tensile stresses propagated about 10 mm in stable tearing prior to plastic collapse, but arrested when entering regions with compressive stresses.