This photo from April 18, 2018, provides a bird's-eye view of Three Mile Island, located in Dauphin County, Pennsylvania. AP Photo
The owner of the closed Three Mile Island nuclear power plant announced plans to restart one of its reactors under a 20-year agreement with Microsoft. This partnership aims to provide carbon-free energy for Microsoft’s data centers. Constellation Energy made this announcement five years after its predecessor, Exelon, shut down the plant due to financial losses and a lack of support from Pennsylvania lawmakers.
The revival of Unit 1 at Three Mile Island comes at a time when interest in nuclear energy is resurging. Policymakers are increasingly recognizing nuclear power as a potential solution to strengthen the electric grid, combat climate change, and meet the growing energy demands of data centers.
Three Mile Island, located just outside Harrisburg, Pennsylvania, is historically significant as the site of the worst commercial nuclear accident in U.S. history in 1979. That incident resulted in the destruction of Unit 2 and left only Unit 1 operational.
With this new agreement, Microsoft is aiming to fulfill its goal of becoming “carbon negative” by 2030, and the energy from the revived reactor will play a crucial role in that mission. Constellation plans to have Unit 1 back online by 2028 and is seeking regulatory approval to operate the plant until at least 2054. The company will need to obtain licenses from the U.S. Nuclear Regulatory Commission, as well as various permits from state and local authorities.
Before the restart can happen, significant investments will be required to restore the plant. This includes repairs to essential components such as the turbine, generator, and cooling systems. Although Constellation did not disclose the estimated costs, experts suggest that restarting the reactor could run into the billions of dollars. Professor Jacopo Buongiorno from MIT estimates that Microsoft may end up paying more than the market rate for the reliable, carbon-free electricity generated by the plant.
While the idea of restarting the plant is feasible, it presents challenges. The success of the restart will depend on the condition of the components and systems that were in place when the reactor was closed. If they were well-maintained during the shutdown, the process could proceed smoothly. However, if the equipment was neglected, Constellation may face a lengthy process of replacement and refurbishment.
A similar situation is unfolding in Michigan, where efforts are underway to restart the Palisades nuclear power plant, which was closed in 2022, backed by a significant federal loan. The collaboration between Constellation and Microsoft is seen as mutually beneficial, as reviving a nuclear plant is typically less expensive than building a new one. Existing infrastructure, such as transmission lines and cooling towers, can significantly lower the costs involved.
The announcement follows a trend where numerous coal and nuclear plants have closed over the past decade due to competition from inexpensive natural gas. This has raised concerns about electric reliability in the U.S. at a time when demand is surging from tech giants that operate large data centers, which are essential for cloud computing and artificial intelligence.
The U.S. is witnessing a concentrated growth in electricity demand, particularly in states like Virginia and Texas, which are becoming hotspots for data centers. Currently, these centers account for about four percent of U.S. electricity use, and projections indicate this could double by 2030.
The agreement between Constellation and Microsoft aligns with broader efforts by the Biden administration and various states to revisit nuclear power as a means to mitigate climate change and reduce greenhouse gas emissions from energy production. Last year, Georgia Power began operations at the first new nuclear reactor built from scratch in decades, marking a significant shift in the U.S. nuclear landscape.
Before its shutdown in 2019, Three Mile Island's Unit 1 had the capacity to generate 837 megawatts, enough to power over 800,000 homes. Unit 2 remains sealed, with its core previously removed to a national laboratory, leaving the site with lingering radioactive materials encased in concrete.
