The Tennessee Valley Authority says bad timing and operator error led to a shutdown of one its nuclear plants in Alabama in December 2012. The utility defended itself today in Atlanta, at a meeting of the Nuclear Regulatory Commission.
A worker at Browns Ferry Unit 2 inadvertently turned off one of the reactor’s key safety systems, leading to a complete shutdown. The reactor was off the grid for almost a week.
NRC officials pressed the utility on if there’s risk of similar events occurring in the future TVA managers say the shutdown only occurred because of an unrelated problem, as workers were trying to bring diesel generators back up to full speed after a routine test. The discussion between the utility and regulators was deeply techincal at times, writes al.com’s Brian Lawson:
But TVA officials contested the NRC’s initial determination that the human error and resulting “scram,” or emergency shutdown, should be classified as a “white finding,” meaning of low to moderate safety significance. TVA contended the finding should be “green,” very low safety significance.
TVA officials said that while the performance deficiency – using supervisors for some field work – had been in place for at least 10 years, it had only resulted in one emergency shutdown. They further argued that the wrong breaker opening would have only resulted in a “half scram” by itself.
The NRC will release its final findings on the incident within 2-3 weeks.
Another nuclear reactor at Browns Ferry has also faced scrutiny from federal inspectors. Two years ago, the NRC slapped Browns Ferry Unit 1 with a safety violation known as a “red finding” for problems with a cooling valve.