Collapse of the Cypress Street Viaduct – Effect on a Postulated Spent Fuel Truck Cask

A recent paper by Ammerman et al. [1] investigated a set of actual transportation accidents and compared them to the hypothetical accident conditions that spent fuel casks are designed to survive. The authors of that paper found the only impact accident that had the possibility of being more severe than the hypothetical accident conditions described in 10CFR71.73 was the collapse of the Cypress Street Viaduct in Oakland during the 1989 Loma Prieta earthquake. Simple hand calculations indicated that had a spent fuel truck cask been on the lower deck of the viaduct when the upper deck collapsed onto it, the crush forces would not have caused the cask to fail, but may have been greater than the forces experienced in the hypothetical accident condition tests. For this reason, this accident was chosen for a more detailed analysis. The results of the more detailed analysis are presented in this paper. The analysis included the actual configuration of the Cypress Street Viaduct and an example spent fuel truck cask. The transient dynamic analysis technique employed accurately predicts the deformations experienced by the cask and the stress state within the cask. These parameters are compared with failure levels to determine if there would have been any release of radioactive material from the example transportation cask.