Don Mosier | Rimini Road
It’s “safe” was the determination of The Nuclear Regulatory Commission (NRC) for Southern California Edison (SCE) and its subcontractor Holtec International to resume spent fuel rod transfer from the cooling pools to the storage receptacles at San Onofre. The “safe” determination was made after a study of the severity of scratching of the stainless steel storage canisters that is now known to occur during the transfer operation, particularly during the lowering of the canister past the guide rings at the top of the “Overpack” receptacle. There are many concerns about the choice of canisters and the ability to relocate them to a safer location, but bear with me while I focus on one seemingly minor issue: the NRC basis for determining that canister scratching does not pose a safety issue.
The NRC and an SCE subcontractor used remote control video cameras to inspect 8 of the 29 canisters already transferred to the vertical receptacles. Although many scratches were detected, analysis of the 3D videos revealed that none exceeded 10% of the wall thickness of half an inch and thus were within basic engineering specifications. This conclusion means that a critical component for long-term storage of highly radioactive waste can have a 10% variance in thickness! The sample of 8 of 29 canisters (28%) allowed the statistical conclusion that no canister had deeper scratches with a 95% certainty. Although 95% probability is a standard threshold for significance in many statistical analyses, that means that there is a 5% probability that the conclusion is wrong. Would you get on an airplane if there was a 1 in 20 chance that it would crash before reaching your destination? Would the NRC bet the lives of 8 million people if there was a 1 in 20 chance that they might be exposed to lethal doses of radiation? What does “safe” really mean to the NRC?
It is likely that fuel transfer will have resumed by the time this article appears. This is not safe by any definition. We need to find a better way to reduce the real risk to our region. I’m 100% certain that there are better options.