Upgrade from Browns Ferry 2 – Nuclear Engineering International

The recent failure of the Browns Ferry 2 SWR included the most extensive work on turbine decks since it was originally built, as well as new fuel innovations.

Above: Browns Ferry 2 resumed generation on April 22nd after completing the final scheduled maintenance and refueling outage (Photo credit: TVA)

BROWNS FERRY, NEAR ALABAMA, USA, is the Tennessee Valley Authority’s largest site.

The plant comprises three General Electric BWRs with Mark I containment. Browns Ferry 1 began commercial operations in December 1973, followed by Unit 2 in June 1974 and Unit 3 in July 1976. All three units were extended by the US Nuclear Regulatory Commission (NRC) for 20 years, allowing them to be in service until the 2030s.

On the last weekend in February, Browns Ferry 2 began a scheduled refueling and maintenance shutdown, which included the most extensive work on turbine decks since it was originally built. All three of the unit’s low pressure turbines have undergone a major component replacement, including new rotors, inner casings, steam pipes and bellows, and turbine monitoring instruments. These tasks required the support of more than 500 additional drop-off workers and an incredible amount of heavy lifting – with 600 separate crane lifts of components such as rotors weighing up to 150 t and inner housings weighing up to 90 t.

The upgrades allow the unit to generate an additional 7 MW of electricity.

“This investment from TVA helps Browns Ferry deliver safe, reliable and clean energy to our local utilities during the peak summer season and beyond,” said Matt Rasmussen, vice president of Browns Ferry’s office. “The work that was completed during this failure shows the high level of commitment our team has for team
our mission of service and for the people who live in the communities we serve. “

Above: Browns Ferry Unit 2 rotor replacement (Image credit: TVA)

Fuel innovations

While major upgrades were taking place on the turbine deck, the refueling team loaded four new 3D-printed fuel assembly supports into the reactor. The brackets show the latest innovations in additive manufacturing and artificial intelligence. They were made at Oak Ridge National Laboratory in a joint project with TVA and utility fuel supplier Framatome as part of Oak Ridge’s Transformational Challenge Reactor program. The components are the first of their kind to be loaded into a commercial reactor.

ORNL additively manufactured channel fastenings for the BWR fuel element from Framatome in the micro-welding process. The team created a 3D printed part that complies with reactor safety regulations for use in a commercial reactor. The laboratory also provides all of the 3D digital data captured during the manufacturing process. It details each layer of 3D printing, information that can be used to certify the quality of the mount.

The channel fixings, which perform an essential function in the fuel bundle, were installed on Atrium 10XM fuel bundles at Framatome’s nuclear fuel manufacturing facility in Richland, Washington.

The channel fastening elements secure the fuel channel on the BWR fuel assembly. The fuel channel wraps around the assembly and directs the flow of coolant up through the fuel rods. Duct fasteners have traditionally been made from expensive castings and required precision machining. Additive manufacturing is an efficient way to meet the tight specifications of these components, explained Framatome.

“The first use of these additively manufactured components supports an innovative manufacturing approach that could pave the way for use in the existing nuclear fleet and in advanced reactors and small modular reactors,” said Dan Stout, TVA director for nuclear technology innovation.

The brackets will remain in the reactor for six years, with inspections scheduled during failures and after removal.

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