Another valve malfunction has been reported at TVA's Browns Ferry Nuclear Plant.
On Thursday, officials with the Tennessee Valley Authority reported to the U.S. Nuclear Regulatory Commission that a high pressure coolant injection system steam line warm-up valve sprang a leak.
TVA's report to NRC said the valve in the unit 2 reactor containment area "was not capable of performing its intended primary containment isolation valve function."
TVA spokesman Ray Golden said the malfunction was minor. He said Brown's Ferry workers' repair of the leaking valve required the closure of another "upstream" valve, and with both valves in a closed position, "the system becomes inoperable and requires the NRC notification."
Golden said the public and employees were never at risk from the event.
"Throughout the event there were multiple safety systems available to cool the reactor as necessary. Unit 2 continues to operate at full power," he said.
Browns Ferry's unit 1 last year was placed under a "red" safety finding from the NRC for a valve failure that went undetected for up to 18 months.
But Golden and NRC spokesman Joey Ledford said this second valve failure is unrelated to the first and is not as serious.
"This is nothing like the [valve failure that led to the] red finding," Ledford said. "This leaking valve did not make the entire safety system inoperable."
Ledford said there was a "pinhole-sized" leak of radioactive steam coming off the pipe, "but it was all in containment. "And it appears to have been promptly discovered and reported and repaired."
He said NRC will continue to review the incident, but he expects it will have no impact on NRC's continuing oversight on TVA as the utility works to get the red finding lifted.
The red finding is the highest and most serious safety rating NRC gives to operating nuclear plants.
NRC has made two rounds of inspections at Browns Ferry since the red finding was announced about a year ago.
Since then, NRC inspectors have told TVA what it must do to improve and return the reactor to "green" or safe status. TVA will make its adjustments and then invite NRC back for a recheck -- a third wave of inspections.
Last month, Preston Swafford, TVA's executive vice president and chief nuclear officer, said the utility is working toward that, "but we're not there yet," he said.