Watts Bar 2, the Tennessee Valley Authority’s (TVA’s) nuclear unit that began commercial operation last October, has been shut down indefinitely owing to a major issue with a condenser revealed this March.
TVA spokesman Jim Hopson told POWER on May 11 that the reactor—the first new nuclear unit to begin operations in the U.S. in more than two decades—was manually shut down on March 23, after the B waterbox of the main condenser experienced a structural failure, causing the loss of the running main feedwater pump, and prompting an automatic turbine trip.
“While the condenser is necessary for the operation of the power generation system, it is not associated with the reactor or reactor safety systems,” Hopson explained. “During shutdown, all systems operated as designed and there were no safety concerns for the public or plant personnel.”
However, Hopson said, TVA is continuing a full assessment of the damage and necessary repairs to the condenser, as well as a detailed root cause analysis. “Early indicators point toward structural members inside the condenser that did not perform as designed, which allowed the normal operating vacuum in the condenser to cause damage,” he said.
The TVA cannot pinpoint a timetable for when the reactor will return to service. “Because of the extremely limited workspace available inside the condenser, we are proceeding slowly and carefully to ensure the safety of our employees and the quality of their repair work,” Hopson said. “As a result, we currently do not have a firm date for a return to service, but hope to have the unit back in operation this summer.”
The 1,150-MW Watts Bar Unit 2, situated 60 miles southwest of Knoxville, Tenn., became the 100th reactor operating in the U.S. when it started commercial operations on October 19, 2016. The reactor saw a long and rocky path to completion since the project broke ground in 1973.
In 1985, lower demand for electricity halted construction of the reactor, and over the years, some of the partially completed unit’s equipment was repurposed for other projects, as POWER has reported. Work resumed in 2008, but owing to schedule slippage, by 2012, cost estimates doubled. In August 2016, just months before the reactor was to come online, a transformer fire delayed power ascension testing.
The TVA returned Watts Bar 1 to service on May 9 after a planned refueling and maintenance outage to help ensure operation for the next 18 months. During the outage, Watts Bar employees—and an additional crew of 800 TVA and contract personnel—upgraded Unit 1’s turbine, conducted inspections of the unit’s reactor equipment and steam generators, and performed maintenance of plant equipment. It also installed “additional enhancements to improve reliability,” the company said.
—Sonal Patel is a POWER associate editor (@sonalcpatel, @POWERmagazine)