One loose bolt inside a fuel storage canister at Southern California Edison's San Onofre nuclear station near San Clemente, Calif., prompted a work stoppage that lasted 10 days, according to Nuclear Engineering International.
The bolt measured only four inches by half an inch. It was found in one of 43 new Holtec International canisters that were to be used for dry storage of spent fuel. Workers discovered the bolt on March 5, while transferring fuel from one of the plant's cooling pools.
The incident came to light during a March 22 meeting. The next day, Holtec said it was investigating the incident and checking the other canisters.
A Holtec project manager, Fred Bidrawn told reporters that the the loose bolt did not affect the integrity of the canister.
The fuel transfers began in January. The report did not say how long the transfer process was expected to take.