The Palisades nuclear plant in Michigan shut down Sunday after workers noticed steam leaking from a drain valve on the piping from one of the reactor’s two steam generators. The shutdown was uneventful, and the NRC has no immediate safety concerns with this issue.
Here’s what happened: The workers were touring the plant’s auxiliary building when they noticed the leak early on Sunday. The leak was in the “secondary” part of the steam generator, not part of the reactor coolant system.
Because the valve could not be isolated from the rest of the steam generator system, the steam generator had to be declared inoperable. The plant’s technical specifications require the licensee, Entergy, to shut down the reactor within six hours when a steam generator is inoperable. Plant operators completed the procedure by 4:30 p.m., meeting this requirement.
The NRC’s resident inspectors responded to the site, observed portions of the shutdown, and made sure there was no impact on other plant equipment.
As the plant cooled, pressure dropped within the steam system, and that stopped the leak. The steam condensed, and the water was collected. It contained small amounts of radioactive tritium, but at levels far below regulatory limits. It will be disposed of as low-level radioactive waste. After shutting down, plant operators vented steam from the same system into the atmosphere through an established monitored release path. This is a common procedure used to help the plant cool down in order to begin repairs.
Palisades remains in cold shutdown while Entergy workers repair the leaky valve. NRC’s inspectors will monitor and assess the repairs, which are expected to take a few days.David McIntyre Public Affairs Officer