Plant officials from the Tennessee Valley Authority’s (TVA’s) Watts Bar nuclear facility said during a senior management meeting presentation that Unit 2—currently under construction—is expected to reach commercial operations on Dec. 13, 2015. Assuming it does, the unit will be the first nuclear reactor added to the U.S. fleet since Watts Bar Unit 1 was brought online in May 1996.
The presentation was given as part of a public meeting in Athens, Tenn., on March 26 to review the project’s status. Staff from the Nuclear Regulatory Commission (NRC) was also on hand to talk about their inspections and other activities taking place, and how the unit would be licensed if it meets all NRC requirements.
“Bulk construction on the plant is complete and we’re in the final phase of completing construction on the remaining systems that are needed to be turned over so that we can perform the final testing on those systems,” said Mike Skaggs, senior vice president for Watts Bar Operations & Construction.
A Storied History
Some would say: “It’s about time!” Construction on the unit began in 1973. It was suspended in 1985 due to slower electricity demand growth, rising construction costs due to inflation and new regulatory requirements stemming from the accident at Three Mile Island in 1979, and regulatory concerns throughout the TVA nuclear fleet.
A study was conducted—beginning in 2006—to evaluate energy needs, schedule, cost, environmental impacts, and financial risks for Unit 2. A decision was made to resume construction, which recommenced in 2008. Although the work has been drawn out, Skaggs suggested that it has been done safely and to very high-quality standards.
“We’re over 32 million man-hours without a lost-time accident,” Skaggs said. “Our quality control acceptance rate on initial inspection is greater than 97%.”
However, the long gap in construction led to some extra work. During the presentation, it was noted that a refurbishment plan had to be developed and approved by the NRC. The plan required a significant number of inspections and tests.
For example, core bore sampling was necessary on previously installed concrete. The samples taken were subsequently broken to verify that the strength satisfied, or exceeded, the original design specification. Steel embedded in the concrete also required evaluation, and all of the buildings were inspected for cracking or any unexpected movement. Skaggs said the building inspections were all satisfactory.
Voltage testing was conducted on cabling to verify that the conductors and the insulation hadn’t degraded or broken down. According to Skaggs, miles of new cabling were installed.
Skaggs said “lots of piping” required replacement, much of it due to design revisions calling for different sizes or grades of material. Borescope inspections were also conducted to verify the internal condition of some piping. A detailed flushing procedure was carried out to ensure pipe cleanliness met requirements.
One unnamed pump vendor was noted to have supplied unsatisfactory equipment. The discovery was made during testing when vibration problems arose. Skaggs said that all of the pumps in question had been reworked and the plant was in the process of getting the last of those pumps and motors into service.
Light at the End of the Tunnel
Preoperational testing was noted to be the current critical path item on the construction schedule. In other words, it is the driving factor in the sequence of tasks that must be completed in order for the project to finish in the shortest amount of time possible with no change in scope.
Open vessel testing, which verifies that safety-related systems used to inject water into the reactor operate as designed, has been completed. The cold hydrostatic test—verifying reactor coolant system integrity—is also done.
Skaggs said the main transformer had been energized and placed in service. Initial vacuum of the secondary side of the plant had been drawn, identifying a few problems, which are being corrected before hot functional testing begins on April 29.
The ice condenser—designed to rapidly absorb thermal energy released inside the reactor containment, thereby reducing pressure in the containment building, if a loss of coolant accident or steam line rupture were to occur—has been cooled. Ice condensers have had a history of operational problems within the nuclear industry. For that reason, TVA performed many inspections and tests on the equipment to ensure its reliability.
“Pretty much all the equipment that either allows the cooldown or moves the air into the ice box have all been refurbished or replaced, and a full testing of that system was performed prior to starting loading ice,” said Skaggs. “We’re 25% complete in loading the ice into the ice condenser.”
Watts Bar is the first facility in the U.S. to report to the NRC that it is in compliance with the Fukushima mitigation strategies order. The plant had to do many things to make that happen, including adding a “FLEX” building, additional diesel generators, a new 500,000-gallon water tank, and portable and pre-staged FLEX equipment, but earlier this month TVA submitted the documents certifying compliance. The NRC expects to begin verifying compliance this week.
Regulatory Obstacles Linger
Although several hurdles remain before the unit enters commercial operation, one of the more significant ones is for the NRC to issue the plant an operating license. NRC Region II Administrator Victor McCree made it sound as if things were progressing smoothly on that front.
“Thus far, our inspections, both done by our residents and our region-based inspectors, have not identified any significant safety concerns that would preclude us—the NRC—from licensing Watts Bar Unit 2,” McCree said.
The NRC says it has expended a total of more than 73,000 hours on inspections at Watts Bar Unit 2 since construction was resumed in 2008, including more than 23,000 hours in 2014 alone. McCree said he expects to see at least as many hours expended in 2015 as were spent last year.
“A tremendous amount of work has been done by both TVA and the NRC to get to this point where we’re having this kind of dialogue. In football terminology, I would say that we’re in the ‘Red Zone,’ but as everybody knows that follows football, that’s where the going gets the toughest. Both organizations have to continue its strong focus on the safe construction of Watts Bar 2 so that the NRC can be in the best informed position it can be to make a decision on a future operator license request,” said Bill Dean, director of the NRC’s Office of Nuclear Reactor Regulation and the man responsible for the Watts Bar Unit 2 licensing decision.
An operating license is needed before the core can be loaded with fuel, planned to begin July 28, 2015. Following that, milestones include full temperature and pressure testing, initial criticality, power ascension to 100%, a unit trip, restart, re-ascension to 100%, a 20-day generation period, and finally, declaration that the unit is commercially operational.
—Aaron Larson, associate editor (@AaronL_Power, @POWERmagazine)