Sequoyah Nuclear Plant now has a “white” safety finding, the first level of safety concerns that triggers stepped up federal inspections, said Nuclear Regulatory Commission (NRC) officials.
Sequoyah, 20 miles from downtown Chattanooga, TN, received notice of the finding in a November letter from the NRC after the plant’s Unit 1 reactor had its fourth unplanned “scram” — or shutdown — in less than a year.
“This was due to two trips [unplanned automatic shutdowns] in the fourth quarter of 2010, one trip in the second quarter of 2011 and one trip in the third quarter of 2011,” wrote Richard P. Croteau, NRC’s director of the division of reactor projects.
A fifth shutdown occurred in the reactor after the plant had moved into the white rating, TVA spokesman Ray Golden said.
White signifies the lowest level of safety concerns, NRC spokesman Joey Ledford said. Red is the highest and in between is yellow.
Neither NRC nor TVA notified the public about Sequoyah’s white rating, officials said, but the letter is on file in NRC’s online documents database.
TVA officials insist the plant is safe and continues to operate.
“The plant is built to be very safe and, while we are disappointed, we want people to understand that at no point was their safety or employees’ safety a problem,” Golden said. “We are committed to finding the root cause [of so many unplanned shutdowns] and to making the plant safer. It’s a continuing learning process.”
Sequoyah is the second TVA plant to trigger a color-coded safety finding.
The Browns Ferry Nuclear Plant, located 70 miles southwest of Chattanooga in Athens, Ala., received a red finding from the NRC in May. The “red, or high safety significance,” finding — the most severe ranking the NRC gives to problems uncovered — is only the fifth issued nationwide in the past decade, NRC spokesmen said.
Reactors with no highlighted problems in six categories are green and, of the nation’s 104 commercial reactors, only about 10 have white, yellow or red indicators. Browns Ferry is the only one with a red finding.
Ledford said the NRC guideline is a reactor can have three unplanned shutdowns in 7,000 operating hours.
“With [Sequoyah’s] fourth one, they crossed the green-to-white threshold,” he said, adding the NRC now plans a special weeklong inspection, probably in February at the plant.
“Right now, there is no indication the scrams are related, but TVA will be looking at the root causes and we will look at all of that,” he said.
“We’re not pleased with that [having two plants with safety issues], but we are working on it,” Golden said. “Hopefully soon we’ll have one back in the green space. But the bottom line for the public is this: We know we operate for their trust.”