Tennessee Valley Authority studies Browns Ferry licence extension

Increased efficiencies from five-year, $475-million Extended Power Uprate make business case for prolonging operation of plant.

Tennessee Valley Authority (TVA) says it is exploring the potential of applying for a 20-year licence extension at Browns Ferry.

The plant’s three reactors are currently licensed to operate to 2033 (Unit 1), 2034 (Unit 2), and 2036 (Unit 3), and the utility recently completed a five-year, $475 million Extended Power Uprate (EPU) which has proved successful. Browns Ferry began operations at Unit 1 in 1973.

“TVA has begun an evaluation on applying for a 20-year extension of the Browns Ferry Nuclear Plant license,” TVA told Nuclear Energy Insider. “The decision will be based on a number of factors, and will be informed by TVA’s recently updated Integrated Resource Plan, which looks at a variety of scenarios and generation sources.

TVA says costs of extending the Browns Ferry license will be part of the evaluation process. Given the size, efficiency and recent EPU upgrade investment, the benefits of a 20-year license extension are clear for Browns Ferry as TVA aims to deliver low-cost energy and reduce carbon emissions.

“We constantly work with others in the utility industry to share lessons learned and best practices,” says TVA. “Part of our evaluation process will include talking to those in the industry who have recently been involved with additional 20-year license extensions for their plants.”

80-year licences

In December 2019, the US Nuclear Regulatory Commission (NRC) approved Florida Power & Light's (FPL) application for a 20-year licence extension for Turkey Point units 3 and 4. That was the first time that the regulator has issued licences authorising reactors to operate for up to 80 years.

The two pressurised water reactors have been in commercial operation since 1972 (unit 3) and 1973 (unit 4) and were initially licensed to operate for up to 40 years. 

The NRC is reviewing applications for subsequent licence renewals from Dominion Energy for Surry 1 and 2 and Exelon for Peach Bottom 2 and 3, while Dominion has formally notified the regulator it intends to apply for a subsequent licence renewal for North Anna 1 and 2.

According to the US Department of Energy, some 20 reactors are planning or intending to operate up to 80 years, with more expected to apply as they get closer to the end of their operating licences.

The Nuclear Energy Institute (NEI) has said that more than half of the US nuclear fleet has expressed interest in 80-year licences, and that rigorous inspections, innovative maintenance and repair techniques, and continuous upgrades will ensure plants continue to operate safely.

Those operators choosing to apply for 80-year licences point to significant cost savings compared with building replacement plants, and the challenges faced controlling new build costs.

Two new reactors being built by Georgia Power at Vogtle were originally estimated to cost $14 billion and come online in 2016. Those estimated costs have nearly doubled to $27.5 billion, with the first reactor entering commercial operation at the end of 2021.

The World Nuclear Association’s Performance Report 2019 showed little variation in capacity factors for both old and new reactors.

Mean capacity factor 2014-2018 by age of reactor

Source: World Nuclear Association, IAEA PRIS

Fuel upgrades

In the meantime, TVA continues to make upgrades at Browns Ferry, including introducing Framatome’s ATRIUM 11 fuel for the three boiling water reactors, with first use planned for 2023.

Framatome will also provide upgrades to the fuel handling equipment across the TVA fleet and steam generator replacements at Watts Bar Nuclear Plant.

This contract makes TVA the third US utility to switch to the ATRIUM 11 fuel design which Framatome says saves utilities money by using the uranium in nuclear fuel more efficiently.

Framatome will upgrade the refuel bridges at Browns Ferry, the manipulator cranes at both Sequoyah units and Watts Bar Unit 1, and the fuel transfer systems at Watts Bar. Framatome previously upgraded the fuel transfer systems at Sequoyah. The company will also replace the spent fuel bridges at Sequoyah and Watts Bar.

SGT, a joint venture between Framatome and AECOM, will also replace four steam generators at Watts Bar Unit 2.

“We are looking to transition to the ATRIUM 11 design as it is more advanced and efficient from a fuel usage perspective,” TVA told Nuclear Energy Insider. “TVA currently has ATRIUM 11 lead test assemblies in Browns Ferry.”

Extended Power Uprate

The EPU project at Browns Ferry resulted in an additional output of 465 megawatts to the grid from TVA’s lowest cost per megawatt facility. Browns Ferry is the first three-unit site to implement EPUs, with the plant generating up to 3,933 megawatts in total.

A dedicated project team worked for nearly two years to develop more than 200 plant modifications.

“Equipment upgrades were implemented to maintain and improve design and operational margins and to eliminate the risk of several reactor trip single point vulnerabilities,” says TVA.

“No additional uprates are planned at this time. Industry operating experience and benchmarking, with particular focus on stations that implemented extended power uprates, was extensively utilized during the identification and development of the modifications to support EPU operation. This contributed to the successful implementation and operational performance of these modifications.”

Scott Birch