Four huge steam generators weighing about 380 tons each have made their way from South Korea to the Watts Bar Nuclear Plant, where they will replace four old generators in Unit 1 that have been operating there for 10 years.
The replacement process is scheduled to begin in the fall of 2006 during a planned refueling and maintenance outage, according to Maureen Brown, senior consultant for communications and government relations at TVA.
The entire project will involve an additional 1,000 contract workers, who will eat and sleep in the Watts Bar area and give a boost to the local economy, she noted.
The new generators, which arrived at Watts Bar on Oct. 30, were transported across the Pacific Ocean in a ship, through the Panama Canal to Mobile, Ala., and up the Tennessee –Tombigee Waterway in barges to the Tennessee River.
They will be stored at Watts Bar until it is time to install them in their own individual concrete compartment within the concrete and steel reactor building.
The replacement process will be very similar to the one at the Sequoyah Nuclear Plant in 2003, when four steam generators were also replaced in Sequoyah’s Unit 1. In all, more than 40 other nuclear units in the United States have successfully completed steam generator replacement projects, according to information provided by TVA.
During the replacement process, according to TVA, residents in the area may hear “loud noises,” similar to that of a jet airplane.
Explaining why steam generators have to be replaced in nuclear reactors, Brown said that over a long period of time, “they develop cracks, and on rare occasions they develop leaks.
“If this occurs they have to be plugged and not used again because, over time, the high pressure, high temperature and continual flow of water and steam wear out the metal used to make the tubes in the early-design process.
“The more tubes that have to be plugged, the less efficient the generator is in making steam.”
Steam generators have a usable life of 12 years, Brown noted, adding that the ones currently installed at Watts Bar were purchased by TVA 20 years before Watts Bar was completed.
She said that “tubing inside the replacement steam generators is made of state-of-the-art material that was not available when Watts Bar was built (1973-1996).” The new generators, she said, have an “improved quality of metal” that provides “better resistance to pressure, temperature and flow, which enhances reliability.”
In order to remove the old steam generators and install the new ones, Brown said, TVA will “shut down the reactor and empty its fuel. A temporary opening will be made in the top of the reactor building and the steel containment structure, and a large crane about 380 feet high will lift each steam generator through the temporary opening.”
Afterward, each old steam generator will be loaded onto a multi-wheeled transporter and moved into storage in a reinforced concrete building with a concrete and metal roof, she said, adding that the new steam generators will be lifted by the crane and lowered inside individual concrete compartments within the concrete and steel reactor building.
When the new steam generators are inside the reactor building, the temporary opening in the roof will be closed by replacing the concrete and steel sections that were cut out. The sections will then be resealed, and the reactor building will be tested to ensure it meets TVA, industry and regulatory requirements.
Brown stressed that the old generators will be no threat to Watts Bar employees, area residents or the environment while they are being removed from the reactor or while they are in storage.
Any openings in the old generators, she said, will be welded shut, and the entire object will be covered with protective plastic sheeting before being removed from the reactor.
TVA said it will also conduct extensive tests of the new steam generators before they begin operation.
Jim Ashley can be reached at jimashley@xtn.net.