Nuclear regulators have called a meeting Monday with TVA officials to probe a failed reactor-core cooling valve that was found "stuck closed" at the Browns Ferry Nuclear Plant.
In an announcement Wednesday, Nuclear Regulatory Commission spokesman Joey Ledford said the valve failure could have hindered a safe shutdown at the Athens, Ala., plant's Unit 1 reactor.
"The valve would have been unable to fulfill its safety function if it had been needed," states the NRC announcement.
Tennessee Valley Authority spokesman Ray Golden said the valve malfunctioned during the October shutdown of Unit 1 for refueling. TVA reactor operators spotted the failure, Golden said.
"When we turned on that equipment, the valve gave us an indication that it was open, but there was no [water] flow going through that gave us an indication that something was wrong," he said.
"In the nuclear industry we always have redundancy and backups. There's a second loop of this equipment, and we immediately turned that loop on, and the valve did open, and we did get flow."
The malfunctioning equipment has been replaced and the valve now is working correctly, he said. TVA tested the malfunctioning valve and determined that water pressure would have forced it open "in about three minutes," he said.
Both Golden and Ledford said the last time anyone is certain the valve worked correctly was in March 2009.
Golden said TVA will have an opportunity to present at Monday's meeting. Then NRC and TVA will discuss the safety significance "of an apparent violation" of NRC regulations.
Ledford said NRC officials will review the information and reach a decision later "on appropriate regulatory action."
David Lochbaum, a Chattanooga nuclear engineer with experience at both Browns Ferry and the NRC, said the stuck valve could have presented a major problem under some circumstances - especially fire, something Browns Ferry has experienced.
He said that to comply with regulations crafted after a March 1975 fire at the plant, TVA had opted to protect one of the dual coolant pumping systems from a possible future fire.
"TVA hung its hat on [this system] surviving to provide cooling water to the reactor. But with this valve broken, and apparently broken for some time, the plant had no assurance of core cooling in event of a fire," he said.
"Sad at any plant, inexcusable at Browns Ferry," said Lochbaum. As nuclear program director for the Union of Concerned Scientists, he testified before Congress twice this week about the Japanese nuclear plant crisis and lessons that may be applied to improve safety in U.S. nuclear plants.
Browns Ferry has three reactors and a design very similar to the embattled Fukushima Dai-ichi Nuclear Plant in Japan. Fukushima remains in varying stages of crisis after system failures on the heels of a 9.0 earthquake and tsunami March 9.
Ledford said the Japan crisis, which prompted NRC to announce a review of all U.S. nuclear safety backup systems, had nothing to do with the NRC announcement of its planned meeting with TVA.