Unit 2 at the US Watts Bar NPP - the first new unit to begin operation in 20 years - began commercial operation on 19 October. The Tennessee Valley Authority (TVA) said the plant "completed an extensive series of power ascension tests and reliably operated at full power for more than three weeks", and had already supplied more than 500GWh of power during testing.
Construction of the two units at Watts Bar NPP in Tennessee first began in 1972, but was suspended in 1985 as nuclear construction slowed in the wake of the 1979 Three Mile Island accident in the US and then the 1986 Chernobyl accident in Ukraine. TVA later resumed work on unit 1, a 1,123MWe pressurised water reactor (PWR), which started up in 1996. However, Watts Bar 1, according to the Atlanta Journal-Constitution, cost $6.8bn, far more than the original price estimate of $370m.
In TVA 2007 decided to complete Watts Bar 2, which had been about 55% complete when construction was suspended. The 1,165MWe PWR reached first criticality in May and was synchronized to the grid in June. Power ascension testing was completed on 3 October. Bechtel served as the primary construction contractor for Watts Bar 2, which has completed eight years of extensive safety reviews and inspections. In October 2015, the US Nuclear Regulatory Commission (NRC) issued TVA with a 40-year operating licence for the Watts Bar 2, allowing the unit to operate until 22 October 2055.
TVA said Watts Bar-2 cost $4.7bn to complete, which, although billions of dollars above the original estimate, fell within the last revision of the project’s final budget, which was in January 2016. TVA had maintained the plant in an incomplete state since 1985 and in 2007 began efforts to complete the plant and updated its operating licence application in March 2009. In 2012, TVA’s board of directors approved the resumption of c work and revised estimated project costs to $4-4.5bn and in January voted to extend the project’s budget by an additional $200m. This was because of cost overruns incurred by regulatory safety requirements that needed to be introduced following the March 2011 Fukushima-Daiichi accident in Japan. Watts Bar NPP was the first site to comply with NRC’s Fukushima-related orders on mitigation strategies and spent fuel pool instrumentation.