Electricity demand could bring Three Mile Island and other shuttered nuclear plants, including the Duane Arnold Energy Center, back to life
Constellation, an energy company that provides electricity and natural gas to customers in 16 states and Washington, announced Sept. 20 that it plans to restore and restart Unit 1 at Three Mile Island, a nuclear plant near Middletown, Pa., that was shut down in 2019. Microsoft has signed a 20-year agreement to purchase electricity generated by the plant to offset power demand from its data centers in the mid-Atlantic region.
Three Mile Island was the site in 1979 of a partial meltdown at the plant’s Unit 2 reactor. The Nuclear Regulatory Commission calls this event “the most serious accident in U.S. commercial nuclear power plant operating history,” although only small amounts of radiation were released and no health effects on plant workers or the public were detected. Unit 1 was not affected by the accident. University of Michigan nuclear engineering professor Todd Allen explains what restarting Unit 1 will involve, and why some other shuttered nuclear plants may also get new leases on life.
WHAT IS THE HISTORY OF TMI-1?
Three Mile Island Unit 1 is a large nuclear power station with the capacity to generate 837 megawatts of electricity — enough to power about 800,000 homes. It started commercial operations in 1974 and ran until September 2019.
After the accident at Unit 2 in 1979, Unit 1 was shut down for six years, until the operator at the time, Metropolitan Edison, demonstrated to the Nuclear Regulatory Commission that it could operate the reactor safely. Constellation closed Unit 1 down in 2019, even though the plant’s operating license had been extended through 2034 and it had no operational or safety problems. TMI-1 could not compete economically at that point with natural gasfueled power plants because gas had become extremely cheap.
Pennsylvania also had a policy preference for increasing electricity generation from solar and wind power. The state legislature chose not to reclassify the plant as a carbon-free electricity source, which would have qualified it for state support.
WHAT IS THE REACTOR’S CURRENT CONDITION?
Since the shutdown in 2019, the plant has sat idle. The NRC calls this status safe storage, or SAFSTOR. The plant is shut down, uranium fuel is removed from the reactor and the facility is maintained in a safe, stable condition. Irradiated fuel is stored in large steel and concrete casks on a physically secured portion of the site, known as an Independent Spent Fuel Storage Installation.
In addition to the fuel, other materials in the plant are radioactive, such as structural channels that direct the cooling water during operation and the large vessel in which the reactor is housed. Radioactive decay occurs during the SAFSTOR period, reducing the plant’s radioactivity and making it easier to dismantle the plant later.
WHAT WILL CONSTELLATION NEED TO DO TO PREPARE THE REACTOR TO RESTART?
Constellation will need to ensure that it has enough fuel and sufficiently trained
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