Three Mile Island Reactor Restarting After 8-Year Shutdown

After sitting idle for eight years, Three Mile Island's Unit 1 reactor is coming back to life with a massive delivery that traveled halfway around the world.

A transformer weighing as much as 40 elephants arrived Monday at the Londonderry Township site in Pennsylvania. The equipment made the journey from South Korea to help reconnect the Crane Clean Energy Center to the regional power grid.

The transformer's job sounds simple but it's crucial. It will boost the facility's voltage from 23,000 volts to 230,000 volts, allowing electricity to flow across the region and power thousands of homes and businesses.

Constellation Energy is leading the $1.6 billion restart project with plans to bring the reactor back online by mid-2027. The plant shut down in 2019 not because of safety issues, but because it couldn't compete economically at the time.

Bryan Hanson, Constellation's Chief Generation Officer, said the facility remains in strong condition. The plant was built to last, and corrective work is now underway to prepare it for its second chapter.

Microsoft has agreed to purchase power from the restarted facility as part of a deal supporting data center operations in Virginia. The electricity will also feed into the broader regional grid managed by PJM, benefiting communities across the area.

The Ripple Effect

The restart couldn't come at a better time for the region's energy needs. Data centers and artificial intelligence are driving unprecedented demand for electricity, and clean energy sources like nuclear power offer a path forward without carbon emissions.

Rob Altenburg of PennEnvironment said the project highlights both an opportunity and a challenge. The region needs considerable amounts of new energy to meet growing demand from large electricity users.

When the reactor restarts, it will add 835 megawatts of carbon-free power to the grid. That's enough electricity to power roughly 800,000 homes while helping to stabilize energy costs and reduce reliance on fossil fuels.

The Unit 1 reactor was never involved in the 1979 accident at Unit 2, which permanently changed America's nuclear industry. Now, nearly five decades later, this facility represents a different kind of milestone: proof that clean energy infrastructure can get a second chance when innovation meets necessity.

Pennsylvania is getting ready to flip the switch on nearly a gigawatt of reliable, emissions-free power.