2014:39 Technical Note, “Wormhole” and Multiple Loss of Buffer Safety Function Scenarios

This Technical Notes reviewed the issues that may cause canister corrosion other than the cases evaluated by SKB, which may belong to “What-if” canister corrosion scenarios. This Notes, in particular, addressed two potential canister corrosion scenarios: “wormhole” formation and loss of multiple buffer safety functions.

The “wormhole” scenario was hypothesized during the SSM Workshop on “What-if” Canister Corrosion and was based on FEP BU07 “piping and erosion of the bentonite buffer” scenario. The subsequent analysis found that the penetration time of the copper canister based on hypothetical size and location of the pipe is shorter than previously predicted. Note that the corrosion analysis was made by assuming that a pipe can be formed. No analysis of how the pipe could form and become stable was conducted. SKB’s study indicated that the piping scenario is impossible for an intact buffer after the buffer is fully saturated. In the “wormhole” scenario, the formation of such a hole was based on the assumption that a locally high gradient of groundwater could contribute to the piping.