In the end, Unit 2 at Three Mile Island was shut down because it was too badly damaged to continue operations. Cleanup for the reactor started almost immediately after the accident in August of 1979. It wasn't completed until nearly 15 years later in December of 1993 at the cost of nearly $1 billion.
Immediately following the accident, the governor of Pennsylvania, Dick Thornburgh, advised that pregnant women and pre-school age children within 20 miles of the reactor should evacuate. This caused nearly 140,000 people to be displaced for almost a month. However, within that time, 98 percent of the evacuees returned to their homes.
There were concerns about the venting of radiological materials into the atmosphere during the accident, and this was the focus of numerous lawsuits against both Metropolitan Edison, the owners, and the various governments of Pennsylvania, the local borough, and the United States. All were dismissed, primarily because studies showed that the release of material amounted to minimal additional exposure to residents.
According to a study released at the time, the average dose to a resident was roughtly 8 millirems, which is about the amount of radiation exposure received from a chest x-ray. Numerous studies by the Pennsylvania Department of Health on residents in the area saw no uptick in the number of cancer diagnoses or a rise in infant mortality.
As far as the nuclear power industry in the United States is concerned, the Three Mile Island incident was a turning point. Because of heightened fears, several other plants under construction were shut down and a temporary ban on new reactors was put into place. While Three Mile Island didn't kill the nuclear power industry, it did put a stop to its historic growth. After the accident, of 129 approved power plants, only 53 were finished. Additionally, no new nuclear power plants were authorized until 2012.