Here is what Wikipedia says about it:
The accident began on Wednesday, March 28, 1979, and ultimately resulted in a partial core meltdown in Unit 2 of the nuclear power plant (a pressurized water reactor manufactured by Babcock & Wilcox) of the Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania near Harrisburg.
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It resulted in the release of a significant amount of radioactivity, an estimated maximum of 13 million curies of noble gases (480 PBq), but under 20 curies (740 GBq) of the particularly hazardous iodine-131, to the environment.[1] However, there are no immediate deaths or injuries to plant workers or members of the nearby community which can be attributed to the accident.
I don’t recall much radioactivity being released. In fact, a dosimeter located in downtown York, PA, about 15 miles away, registered no change in radioactivity during the whole “crisis”.