Three Mile Island Reactor Restarted for Microsoft's AI Data Centers

The 1979 Three Mile Island Accident

• 💥 On March 28th, 1979, a cooling malfunction and subsequent human errors at the Three Mile Island Unit 2 reactor led to a partial meltdown, the worst nuclear incident in US history.
• ⚠️ A stuck relief valve and undetected pressure drops caused the reactor core to overheat, releasing radioactive gas and necessitating the evacuation of approximately 140,000 people.
• 📉 Despite the severity, there were no reported injuries or deaths, but the accident led to stricter regulations for the nuclear industry.

Unit 1's Operational History and Shutdown

• ⚡ Unit 1, a separate reactor at the site, continued operating for another 40 years after the Unit 2 accident.
• 📉 It was eventually shut down in 2019 due to struggles competing with cheaper energy sources like natural gas and renewables, leading to decommissioning.

Microsoft's Deal and the Crane Clean Energy Center

• 🤝 Constellation Energy struck a deal with Microsoft to relaunch Unit 1 under the new name, Crane Clean Energy Center.
• 💡 Microsoft will purchase carbon-free power directly from the site for approximately 20 years to meet its massive energy demands for data centers, particularly for artificial intelligence development.
• ⚡ The restarted reactor is expected to contribute over 800 megawatts of power to the grid.

Restarting a Decommissioned Reactor

• 🛠️ Bringing Unit 1 back online is less complex than dismantling it because it was placed in a "safe store" or "mothballed" state after shutdown, with fuel removed and systems preserved.
• ⏳ The restart process is extensive, involving evaluating component conditions, retrofitting systems, and performing maintenance, projected to take 4 years and cost over $1.5 billion.
• 📈 Despite its aged appearance, the control room has been updated with modern safety features and rigorous testing ensures reliability.

Broader Trends in Nuclear Power Restart

• 🚀 Other plants like Palisades in Michigan and Duane Arnold in Iowa are also undergoing restarts, benefiting from similar "safe store" preparations.
• 🚧 Building new nuclear reactors in the US has become significantly more challenging and time-consuming due to stringent regulations implemented after the Three Mile Island incident and other past accidents.
• 💡 Restarting existing, safely stored reactors is seen as a more feasible way to increase nuclear power capacity to meet growing energy demands, especially for power-hungry tech industries.