The TMI Reactor was a nuclear power plant for generating electricity with nuclear fission. It is on the Susquehanna River, with two main units: TMI1 and TMI2. TMI2 was the one that had a meltdown. It was created for cheaper and cleaner energy.
"Atomic energy is capable of application for peaceful as well as military purposes."
USC - Congressional declaration of policy
People in the vicinity had gotten used to the power plants dominating everything, and were optimistic for cheaper and clearner energy; but they were also nervous about the destructive power of an accident, the fear that started when countries started competing for nuclear superiority.