The Nuclear Regulatory Commission (NRC) has extended the expiration date of the construction permit for the unfinished Unit 2 at the Watts Bar Nuclear Power Plant (WBN) to Sept. 30, 2016.

WBN is located about 10 miles south of Spring City, Tenn., and is owned by the Tennessee Valley Authority (TVA). TVA requested the extension on May 17, 2012.

Unit 2 has had a long and storied history. Ground was broken on Unit 2 in 1973. However, construction 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. At the time, Unit 2 was estimated to be 80% complete with a total investment of about $1.7 billion.

In the years that followed, various pieces of equipment, such as pumps, motors, and valves, were salvaged for use in Watts Bar Unit 1 or in Watts Bar’s sister plant, Sequoyah. A Detailed Scoping, Estimating and Planning (DSEP) study in 2007 found Watts Bar Unit 2 to be effectively 60% complete and estimated that Unit 2 could be finished in about 60 months at a cost of about $2.5 billion.

In 2008, construction resumed on Unit 2 and the NRC extended the construction permit to March 2013. Even with that extension, the project continued to experience delays and cost overruns.

TVA evaluated and updated its completion schedule in 2010. A root cause analysis cited four major factors that led to an extended schedule and higher costs to complete Unit 2: project leadership, original estimate, project execution, and project oversight. However, by August 2011, the company was again announcing further delays.

In April 2012, the TVA board approved continued completion of Unit 2 in accordance with a revised estimate. The decision was at least partly based on the fact that a new leadership team was in place, shortcomings that led to schedule delays had been identified, new processes and management systems were being installed to better track progress, the workforce had been reduced to a more manageable size, and productivity was rising.

The changes seem to be working. In the latest quarterly update, issued by TVA on Oct. 29, 2013, the company noted that the project remains on track for completion by December 2015 and within a cost range of $4 billion to $4.5 billion.

—Aaron Larson, associate editor (@AaronL_Power, @POWERmagazine)