CHATTANOOGA, Tenn., May 10, 2011 /PRNewswire-USNewswire/ -- The Tennessee Valley Authority announced Tuesday that it is working with the Nuclear Regulatory Commission to address issues related to concerns about the performance of a valve at the Browns Ferry Nuclear Plant in Alabama. TVA noted that it found and reported the problem, repaired and tested the valve and that the NRC agrees that the plant is operating safely.
The valve is part of a residual heat removal system, which helps keep reactors properly cooled during routine operations and in the event of a fire or other emergency. The NRC issued a "red finding" related to the valve's performance, which denotes high safety significance.
"TVA found the problem and fixed it," Chief Nuclear Officer Preston Swafford said. "A manufacturing defect in the valve stem threads, which are designed to screw into the valve disc, were determined to be too small. We made repairs and reinstalled the valve. It has worked properly during tests, and it worked properly again last week when the plant really counted on it after the severe weather that recently hit Alabama."
Swafford said the NRC indicated Tuesday that this violation would not affect Browns Ferry's return to service when repairs are completed to the area's tornado-damaged network of power lines, which prompted the plant to safely shut down last Wednesday.
Swafford said TVA is "considering our options" in responding to the NRC finding. A "red" finding under the NRC's Reactor Oversight Process results in increased NRC inspections and oversight at Browns Ferry. The NRC inspection findings are evaluated using a safety significance scale with four levels, ranging from "green" for minor significance, through "white" and "yellow" to "red" for high significance.
The "red" finding was the culmination of a seven-month process to determine the safety significance when one of two independent residual heat removal valves failed to immediately open when placed in service during an October 2010, Unit 1, Browns Ferry Nuclear Plant refueling outage.
"Obviously we're disappointed with the NRC's findings on this matter," Swafford said. "The safe operation of all our units is our primary concern, and we take any regulatory report of a violation very seriously."
The valve and the entire residual heat removal system are important parts of the plant's overall safety system. Browns Ferry is currently upgrading its fire protection program to the NRC-endorsed performance based standard (NFPA 805).
"We've worked hard at Browns Ferry to address a number of fire risk concerns, and moving to the NFPA 805 requirements will further help us improve that fire risk margin," Swafford said. "We have multiple redundant safety systems in place to assure proper performance and safe operations in the event of fires or other emergencies."
He noted that TVA also is upgrading other systems to make the equipment that uses the valves less critical to the overall ability of the plant to safely shutdown in the event of a fire or other emergency.
"TVA regularly performs comprehensive and detailed analyses on the safety systems at Browns Ferry," Swafford said. "Even without the repairs, we believe the valve would have performed as designed in an actual operational event. Our forensic analysis demonstrates that the problem was related to a manufacturing defect, not human performance."
The Tennessee Valley Authority, a corporation owned by the U.S. government, provides electricity for utility and business customers in most of Tennessee and parts of Alabama, Mississippi, Kentucky, Georgia, North Carolina and Virginia – an area of 80,000 square miles with a population of 9 million. TVA operates 29 hydroelectric dams, 11 coal-fired power plants, three nuclear plants and 11 natural gas-fired power facilities that can produce about 34,000 megawatts of electricity, delivered over 16,000 miles of high-voltage power lines. TVA also provides flood control, navigation, land management and recreation for the Tennessee River system and works with local utilities and state and local governments to promote economic development across the region. TVA, which makes no profits and receives no taxpayer money, is funded by sales of electricity to its customers. Electricity prices in TVA's service territory are below the national average.
SOURCE Tennessee Valley Authority