This file photo of April 2007, released by the Tennessee Valley Authority, shows the cooling tower of the single operating reactor at the Watts Bar Nuclear Plant in Spring City, Tenn.TVA has ordered an unpaid safety "stand down" at Watts Bar Nuclear Plant for about 1,000 contract workers after finding cables had been erroneously removed from Unit 1 - the operating reactor - in December.
In another mistake last week, a valve in Unit 2, the reactor now under construction at the plant, also was removed from another system without workers following proper guidelines.
Mike Skaggs, TVA's senior vice president for nuclear generation, development and construction, ordered the stoppage - known as a "stand-down" - to start at noon Wednesday "until the errors discovered are clearly communicated to all personnel," along with TVA's demand for quality work, according to TVA spokeswoman Barbara Martocci.
No one was hurt, she said, and at no time was the safety of the public put at risk.
Longtime TVA workers could not recall another stand-down of this size, she said.
"We're taking the construction of the plant seriously as far as the health and safety of our employees," she said. "This sort of thing is necessary when we find errors that could have been prevented and weren't."
The problems were discovered in normal TVA inspections, but they pile another layer of safety concerns on the utility that already faces heightened scrutiny from the Nuclear Regulatory Commission at all three of its nuclear plants.
Last summer, NRC placed TVA's Browns Ferry plant near Athens, Ala., under a red finding - the regulator's most serious safety flag.
In November, NRC placed Sequoyah Nuclear Plant outside Chattanooga under a white finding, the lowest safety rating, because the plant had too many unplanned reactor shutdowns in less than a year.
In December, TVA disclosed that the NRC had raised another white safety flag at Watts Bar for concerns within the security division.
Under NRC's color-coded inspection findings, white is least serious, then yellow, then red. A plant operating with no safety problems is coded green.
NRC spokesman Joey Ledbetter said the commission's resident inspectors at Watts Bar are following up on the most-recent incidents.
"It is too early to say if we will take any action," Ledbetter said.
Watts Bar Unit 1 reactor is the nation's youngest, operating since 1996, and the plant's new twin reactor, Unit 2, is still under construction. TVA has color coded the two reactors to help workers know they are working on the correct reactor.
Nonetheless, Martocci said the contractors who removed the cables from a set of backup pressurizer heaters were working on the wrong reactor.
In the second incident, the valve that was removed was tagged with specific instructions, and those instructions were not followed, she said.
Ledbetter and Martocci said the unusual action of ordering a widespread stand-down is a tool designed to get the attention of the workforce.
"It gives management an opportunity to communicate the importance of a strong safety culture," said Ledbetter.
Martocci said TVA managers on Thursday were required to come up with ways to talk to and train - perhaps even retrain - workers to be more mindful of safety rules and processes.
On Monday, some of those talks and training sessions will begin, she said.
"Although the workers may have lost a day and a half's pay, this stand-down could save a life by ensuring everyone follows procedures and remains safe every day they come to work," she said.
Last year, two contractors were charged federally with falsifying inspection records on nonexistent electrical cables at Watts Bar.
David Lochbaum, a longtime advocate of safer nuclear systems and the director of the Nuclear Safety Project for the Union of Concerned Scientists, said the incidents involved little-used, redundant systems that only in worst-case scenarios might have tripped a reactor. But he agreed with the action taken to get workers' attention.
"It's the right thing to do. It's like a timeout for workers to refocus," said Lochbaum, a former TVA nuclear operator and a former NRC training instructor.