The NLI-1/2 Tipover Accident

On March 11, 1988, an empty NLI -1/2 truck cask tipped over while negotiating a right-hand turn on the Rockwell International Corporation (Rocketdyne) site in Canoga Park, California . The cask had been used to transport fuel to Idaho for the USDOE and was returning for another cask load, so the cask was empty at the t i me of the accident. The truck tractor remained upright, but the trailer turned over on its side, warping the trailer frame . The tractor/trailer rig was not speeding, and fortunately the driver was not injured in the accident . The cask was undamaged as the wooden impact limiters crushed sacrificially to protect the cask, and no radioactive material was released. Post-accident analysis determined that the cask center-of-gravity (CG) was high and the trailer frame was not stiff enough to resist the overturning forces of a reasonably sharp turn. Corrective action included changing the trailer to a stiffer frame with a drop-frame design to lower the cask center-ofgravity . The cask was returned to service after hydrostatic pressure tests and inspections showed that the cask was undamaged.