Constellation to restart Three Mile Island unit, powering Microsoft

Constellation purchased the 837 MWe Three Mile Island Unit 1, in 1999. The unit, which had enough capacity to power 800,000 homes, was retired prematurely for economic reasons in 2019. In its last year of operation, the plant was producing electricity at maximum capacity 96.3% of the time – well above the industry average and employed more than 600 full-time workers.

The Unit 1 reactor is located adjacent to TMI Unit 2, which was shut down in 1979 after an accident which resulted in severe damage to the reactor core and is in the process of being decommissioned by its owner, Energy Solutions. 

Constellation says “significant investments will be made to restore” unit 1 “including the turbine, generator, main power transformer and cooling and control systems. Restarting a nuclear reactor requires US Nuclear Regulatory Commission approval following a comprehensive safety and environmental review, as well as permits from relevant state and local agencies. Additionally, through a separate request, Constellation will pursue licence renewal that will extend plant operations to at least 2054”.

The plant is to be renamed the Crane Clean Energy Centre – after Chris Cane, who was CEO of Constellation’s parent company and passed away in April. The aim is for it to be online in 2028. Constellation says it aims to operate it for decades to come, and will create 3400 direct and indirect jobs and deliver more than USD3 billion in state and federal taxes

“This agreement is a major milestone in Microsoft’s efforts to help decarbonise the grid in support of our commitment to become carbon negative. Microsoft continues to collaborate with energy providers to develop carbon-free energy sources to help meet the grids’ capacity and reliability needs,” said Bobby Hollis, vice president of energy, Microsoft.

Joe Dominguez, president and CEO, Constellation, said: “Powering industries critical to our nation’s global economic and technological competitiveness, including data centres, requires an abundance of energy that is carbon-free and reliable every hour of every day, and nuclear plants are the only energy sources that can consistently deliver on that promise. Before it was prematurely shuttered due to poor economics, this plant was among the safest and most reliable nuclear plants on the grid, and we look forward to bringing it back with a new name and a renewed mission to serve as an economic engine for Pennsylvania.”

Governor Josh Shapiro said: “Under the careful watch of state and federal authorities, the Crane Clean Energy Center will safely utilise existing infrastructure to sustain and expand nuclear power in the Commonwealth while creating thousands of energy jobs and strengthening Pennsylvania’s legacy as a national energy leader.”

Michael Goff, Acting Assistant Secretary, Department of Energy’s Office of Nuclear Energy, said: “Always-on, carbon-free nuclear energy plays an important role in the fight against climate change and meeting the country’s growing energy demands.”

Friday’s announcement could see the unit become the second in the USA – and the world – to return to operational status after being shut down for decommissioning. Holtec International is currently working to bring the Palisades single-unit pressurised water reactor in Michigan, which closed in 2022, bring back into service and is aiming to repower the plant by the end of 2025.

Earlier this year, the US Department of Energy Loan Programs Office conditionally committed up to USD1.52 billion for a loan guarantee to Holtec Palisades for the project, and in June US Energy Secretary Jennifer Granholm told Reuters she would be “surprised” if the office was not talking to other owners of shuttered plants about potential restarts.