© n/a
In the immediate aftermath of the detection of a leak in the piping of a recently installed steam generator, officials downplayed any potential threat, noting that the amount of radiation leaked was so small that Nuclear Regulatory Commission rules did not call for a mandatory shutdown. Later it was disclosed that radioactive gas from the leak had been vented to an auxiliary building that did not have the same safety seals to prevent radiation from being released into the atmosphere as are found on the reactor.
Once the Unit 2 reactor was shut down, it was discovered that hundreds of tubes on the generator, replaced in 2009 as part of a $670 million-plus overhaul using components supplied by Japan-based Mitsubishi Heavy Industries, had suffered significant deterioration over their relatively short service lives. Aside from the one tube known to have failed at Unit 3, two tubes at Unit 2 were found to have more than a third of their thickness worn away, requiring them to be plugged and incrementally increasing the burden on the remainder of the 9,700 tubes in the system. While only these two were worn to the point of needing to be taken offline as a safety precaution, 69 other tubes showed deterioration of at least 20 percent, and more than 800 had thinned by 10 percent or more.
