TVA safely shut down its Browns Ferry Nuclear Plant in Alabama with emergency backup power this week, but power outages across the Tennessee Valley still left the utility without enough emergency sirens to warn nearby residents of potential safety problems at both Browns Ferry in Alabama and the Sequoyah Nuclear Plant near Soddy-Daisy.
In a notice to the U.S. Nuclear Regulatory Commission released Friday, TVA said more than 60 percent of its sirens around Browns Ferry and about a third of its warning sirens around Sequoyah were inoperable this week when electricity service was lost to the sirens following Wednesday's tornadoes and wind storms.
With so many sirens not working, TVA has had to be prepare plans to use police vehicles with loud- speakers to notify residents living within 10 miles of the plant should a nuclear accident occur.
Most of the sirens were back in service Friday night at Sequoyah, according to NRC spokesman Ken Clark. But at Browns Ferry, TVA is still struggling to regain power after storms knocked down 90 transmission lines across TVA's seven-state region, including all of those in Alabama. As of Friday night, 21 of those transmission lines were back in service, TVA spokeswoman Barbara Martocci said.
TVA is relying upon its diesel-fired generators to provide power to circulate water into the spent fuel ponds and the reactor core of the Browns Ferry plant, where all three reactors shut down during the Wednesday storm.
"The diesel generators are operating as they should, and we still have one 161,000 kilovolt line to Browns Ferry," TVA spokesman Ray Golden said Friday night. "We hope to get a second line to the plant over the weekend."
TVA had to declare "an unusual event" - the lowest of four categories of alert at a nuclear plant - after the utility lost power to the three-unit Browns Ferry plant. TVA has used eight diesel generators and one of five transmission lines still operating to the plant to maintain Browns Ferry operations. The addition of a second 161,000-volt transmission line would allow TVA to be removed from the "unusual event" classification, Clark said.
But before any of the reactors is started up for power generation, the two major 500,000-volt lines at the plant will have to be restored to service.
At Sequoyah, the plant has continued normal operations, but EPB and other TVA distributors lost power lines serving some of the 108 sirens around Sequoyah.
"We are working to eventually replace these sirens with equipment that will have dual capabilities [for electric or battery operation]," Golden said.