Since the Tennessee Valley Authority (TVA) experienced an oil fire at the switchyard serving the Watts Bar nuclear station on Aug. 30, the federal utility has decided to do extensive work at the switchyard prior to full commercial operation of Watts Bar 2.
The fire forced the Watts Bar 2 nuclear unit offline not long after it had achieved 99% power output as part of increasing generation tests. As a precaution, TVA also took Watts Bar 1 offline temporarily on Sept. 1 so workers could safely inspect de-energized equipment in its switchyard.
Watts Bar 1 has since gotten back to 100% power, while Watts Bar 2 remains at zero power.
There is a “dual” switchyard at the Watts Bar nuclear complex and it has both 161-kV and 500-kV facilities, TVA spokesperson Jim Hopson told GenerationHub on Sept. 12.
The fire occurred on the “station side” of the switchyard serving Watts Bar 2, Hopson said. TVA cannot yet give an accurate prediction of either the cost of the switchyard repair or the length of time it will take to complete, he added. Work will be done by TVA’s in-house employees.
“We’ve got to fully understand what happened,” before that is determined, Hopson said. The transformer is an extremely large facility and the examination includes draining oil out.
“It’s a fairly extensive process,” Hopson said. “We want to make sure that it’s done right,” before Watts Bar 2 officially enters commercial operation.
Like TVA President and CEO Bill Johnson, the TVA spokesperson said that “commercial operation” is largely an “accounting term” that distinguishes capital expense projects from “operating and maintenance” expenses.
The Watts Bar 2 nuclear unit has been generating increasing levels of power this summer although it has yet to officially be deemed in commercial operation.
The deployment of Watts Bar 2 will mean that a second 1,150-MW nuclear reactor will be using the switchyard, Hopson noted.
TVA has not yet filed any reports on implications of the Aug. 30 fire, and subsequent repair project, with any federal agencies aside from the initial “event report” filed with the Nuclear Regulatory Commission (NRC). The NRC inspector on-site is well aware of the situation, Hopson said.
TVA connected the long-anticipated Watts Bar 2 to the grid in early June. After the NRC issued an operating license for the unit last October, 193 new fuel assemblies were loaded into the reactor vessel the following month. TVA announced at the end of May that the reactor achieved its first sustained nuclear fission reaction.
Initial construction on Watts Bar 2 originally began back in 1973, but construction was halted in 1985 after the NRC identified weaknesses in TVA’s nuclear program, according to the Energy Information Administration (EIA).
In August 2007, the TVA board of directors authorized the completion of Watts Bar 2, and construction started in October 2007. At that time, a study found Unit 2 to be effectively 60% complete with $1.7bn invested. The study said the plant could be finished in five years at an additional cost of $2.5bn. However, both the timeline and cost estimate developed in 2007 proved to be overly optimistic, as construction was not completed until 2015, and costs ultimately totaled $4.7bn.