Nuclear

Watts Bar Unit 2 is back in service with four new steam generators

The original steam generators were built in the 1970s using a metal alloy that prematurely developed leaks and other problems at other nuclear plants.

The Tennessee Valley Authority’s Watts Bar Unit 2 is America’s newest commercial nuclear reactor and may also have the newest set of steam generators.

The Steam Generating Team (SGT), a joint venture between Framatome and United Engineers & Constructors, Inc., said in early November it completed the steam generator replacement project at the 1,150 MW facility in eastern Tennessee. 

Operated by TVA, Unit 2 entered service in 2016 at a construction cost of $4.7 billion.

The original steam generators were built in the 1970s using a metal alloy that prematurely developed leaks and other problems at other nuclear plants.

The equipment was installed at Watts Bar in the 1980s before TVA halted work at the site due to cost overruns, employee safety concerns and a drop in projected power demand. 

TVA determined it would be too costly to replace the original steam generators when construction resumed, so Unit 2 entered service as America’s newest reactor with its original steam generators, potential flaws and all.

The cost to replace the steam generators this year rose to around $590 million and took weeks longer to install than originally expected due to weather issues.

Steam generator lift at Watts Bar Unit 2. Credit: Framatome

In February 2020, TVA awarded Framatome several contracts for work across the company’s reactor fleet. This included fuel for the Browns Ferry nuclear power plant, fuel handling equipment upgrades across the fleet and steam generator replacements at Watts Bar 2.

To remove and replace the 67-foot, 360-ton steam generators through the Unit 2 reactor building, temporary openings in the reactor building dome, containment and steam generator enclosures were required. 

During the replacement, Framatome provided expertise in decontamination, metrology, machining and welding. It also introduced a technology that provided precision welding capabilities critical for connecting the replacement steam generator to the primary piping of the reactor. SGT provides heavy component replacement services and other major projects to the nuclear industry. 

Steam generators serve as heat exchangers in pressurized water reactors. The components use the heat generated by the reactor to create steam that drives the turbines, which turns a generator and creates electricity.