The Three Mile Island nuclear power station in Pennsylvania is scheduled to close in September according its owner, Exelon Generation. The site of the worst nuclear disaster in US history, the still functioning Three Mile Island Generating Station Unit 1 (TMI-1) will be deactivated on September 30, 2019 due to financial difficulties resulting from lack of progress of a support bill in the state legislature.

On March 28, 1979, Three Mile Island Nuclear Generating Station Unit 2 (TMI-2) in Dauphin County, Pennsylvania suffered a partial meltdown of its reactor core due to a number of design flaws and poor decisions in handling a loss of coolant incident. Problems in the non-nuclear secondary system were followed by a stuck relief valve in the primary cooling system, resulting in the loss of large amounts of coolant.

This would have been bad enough, except that poor control and interface designs caused the operators to commit a series of errors that resulted in a cascade of malfunctions that resulted in the core overheating and the release of radioactive noble gases and iodine isotopes into the atmosphere.

Though there were no fatalities or injuries from the accident and the health effects from the radioactive release were deemed statistically insignificant, the accident had long-range political effects as support for nuclear power collapsed in the United States and many other Western nations.

Though TMI-2 was shut down and decommissioned, TMI-1 continues to operate today. However, the present owner of TMI-1, Exelon Generation, ran into financial difficulties involving refueling. Two bills for relief were introduced into the Pennsylvania state legislature, House Bill 11 and Senate Bill 510, but no action was taken to advance them. With the legislative session coming to a close, Exelon has decided to shut down the reactor prematurely and filed the federally required Post Shutdown Decommissioning Activities Report with plans for TMI-1 after its final shutdown.

"Today is a difficult day for our employees, who were hopeful that state policymakers would support valuing carbon-free nuclear energy the same way they value other forms of clean energy in time to save TM-I from a premature closure," says Bryan Hanson, Exelon senior vice president and chief nuclear officer. "I want to thank the hundreds of men and women who will continue to safely operate TMI through September. We will offer a position elsewhere in Exelon to every employee who wishes to stay with the company and is willing to relocate, and we will do all we can to support the community, the employees and their families during this difficult period."

Source: Exelon