ATLANTA (AP) - The Tennessee Valley Authority has fixed the immediate problems that led to a serious safety violation at its Browns Ferry nuclear plant in Alabama, but it must still demonstrate long-term improvement, federal regulators said Thursday.
The initial findings by the U.S. Nuclear Regulatory Commission come from an in-depth inspection triggered by a serious safety violation issued in mid-2011 against the plant near Athens, Ala. The NRC had issued only five such red findings - its most severe citations - up to that point. It came after the agency investigated how a valve on a cooling system on the Unit 1 reactor became stuck shut, which could have left equipment used to cool hot, radioactive nuclear fuel inoperable.
The plant still had other cooling systems. But the failure would have been a major problem during a fire since emergency plans called for preventively shutting down other equipment and using the damaged system.
Federal authorities were troubled because workers failed to quickly notice that the valve was broken, pointing to a weak safety culture. The equipment failure, uncovered in 2010, never caused a serious problem at the facility.
"They have a higher regard for a stronger safety culture at the station," said NRC branch chief Eugene Guthrie, who oversees the federal inspectors at the plant and headed the in-depth inspection. "It starts there. But all of that needs to be reinforced in the worker behaviors as they perform their routine duties and responsibilities in the field."
NRC officials still rank the Unit 1 reactor at Browns Ferry as one of the worst-performing nuclear plants in the country. Federal officials will rely on the results of future inspections and reviews to determine whether they upgrade the plant's rating, which affects the level of NRC scrutiny it receives.
The TVA's chief nuclear officer, Preston Swafford, called the inspection thorough and "appropriately intrusive."
"TVA agrees with the NRC assessment that we have additional work to reach and sustain excellence," he said in a statement.
The intensive review uncovered potential low-level violations, though they are not considered serious. Guthrie declined further comment on those issues, though they will be made public later. A final inspection report is expected in August.
Federal regulators considered the stuck valve a prominent example of similar problems dogging the plant. Around the same time, plant workers installed a bearing backward and failed to correctly diagnose other damaged equipment. The reactor had to be unexpectedly taken offline more frequently than others in the industry.
During the three-part inspection, NRC officials checked whether other valves could be affected, reviewed the rigor of the TVA's testing and maintenance programs and conducted hundreds of interviews to delve into the plant's safety culture, a review that finished in May.
NRC inspectors say they now believe the Browns Ferry plant is operating safely, has increased its overall performance and is working through an improvement plan. One of the TVA's major tasks has been catching up with maintenance work that slipped, contributing to an increase in equipment failures.
"What was happening was there (were) thousands of preventive maintenance activities that they had not performed over several years on the safety system, which created a significant backlog," Guthrie said. "By not performing that preventative maintenance, it was directly affecting the reliability of those systems."
David Lochbaum, director of the nuclear safety project for the Union of Concerned Scientists, said he believed the inspection was just right - not too harsh, not too lenient. Still, he had questions about whether the utility's culture was improving.
Statistics published by the NRC show that workers from Browns Ferry make more anonymous complaints to the NRC than most other plants in the industry. While a lack of anonymous whistleblower complaints would be suspicious, Lochbaum said workers in well-run plants should be making fewer whistleblower reports because they can report issues to their own company without fear.
"I'd feel better if that number was trending down," said Lochbaum, who worked as a reactor engineer at Browns Ferry from 1980 to 1983.
Browns Ferry has a troubled history. In 1975, a worker using a candle to check for air leaks started a fire that was considered the most serious industry accident until a meltdown happened four years later at Pennsylvania's Three Mile Island plant. TVA voluntarily shuttered its entire nuclear fleet in 1985 to address safety and performance issues. The Unit 1 reactor at Browns Ferry reopened in 2007.
TVA supplies electricity to about 9 million people in Alabama, Georgia, Kentucky, Mississippi, North Carolina, Tennessee and Virginia.