What Happened At Three Mile Island? Power Plant Where Worst Nuclear Disaster In US Occurred Set To Close

Three Mile Island, the site of the United States’ worst nuclear disaster, will close down for good in 2019. Exelon Corp., the company that owns the nuclear power plant, announced the closure Tuesday.

The company cited high operating costs and a recent failure to auction off the plant’s power into the regional power grid as part of the reasoning for the plant’s permanent closure. Almost 700 people were set to be laid off as the plant shuts down.

“Today is a very difficult day, not just for the 675 talented men and women who have dedicated themselves to operating Three Mile Island safely and reliably every day, but also for their families, the communities and customers who depend on this plant to produce clean energy and support local jobs,” Exelon CEO Chris Crane said in a statement Tuesday.

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Three Mile Island, so-named for the island on Pennsylvania’s Susquehanna River where it’s located, suffered a partial meltdown Mar. 28, 1979. The accident began when a non-nuclear section of the plant failed, causing the pumps that cool the reactor's core to fail. A confluence of equipment malfunctions, design-related problems and worker errors led to the meltdown, according to the U.S. Nuclear Regulatory Commission.

While the levels of radioactivity released were relatively low and caused no significant health impacts on the public or the plant’s workers, the ensuing nuclear disaster was the worst to ever occur in the U.S. before or since. Critics of nuclear energy used the Three Mile Island accident as justification for ending nuclear energy, while proponents of nuclear power argued that the meltdown proved that even in times of failure, nuclear energy could be relatively safe.

Flash forward 38 years, and the plant won’t be staying open long enough to be eligible for renewal of its federal license in 15 years. Exelon cited the energy marketplace in Pennsylvania that does not allow nuclear power to compete adequately as part of the reason for the plant's closure. Pennsylvania ranks as the state with the second most nuclear capacity in the country, second only to Illinois.

“Despite producing 93 percent of the Commonwealth’s emissions-free electricity and avoiding 37 million tons of carbon emissions – the equivalent of keeping 10 million cars off the road every year – nuclear power is not included in the state’s Alternative Energy Portfolio Standard,” Exelon said in its press release.

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Three Mile Island was shut out of a critical auction last week conducted by PJM Interconnection that incapacitated its ability to sell electricity in 2020 and 2021, according to Lancaster Online.

“Like New York and Illinois before it, the Commonwealth has an opportunity to take a leadership role by implementing a policy solution to preserve its nuclear energy facilities and the clean, reliable energy and good-paying jobs they provide,” Crane said in the press release. “We are committed to working with all stakeholders to secure Pennsylvania’s energy future and will do all we can to support the community, the employees and their families during this difficult period.”