What was the name of the nuclear power plant in Pennsylvania which had a frightening radiation leak in 1979?

In March 1979, a partial meltdown of a reactor at the Three Mile Island Nuclear Generating Station near Harrisburg, Pennsylvania, became the most serious accident in the history of the U.S. commercial nuclear power industry. The incident began with a relatively minor malfunction in the plant's secondary, non-nuclear section. This triggered a series of events, compounded by a relief valve that stuck open and human error, which led to a loss of coolant and the subsequent overheating of the reactor core.

While the reactor's containment building largely prevented a catastrophic release of radiation, some radioactive gases did escape into the atmosphere. This led to widespread fear and the voluntary evacuation of approximately 144,000 people from the surrounding area. In the immediate aftermath, there was concern over a hydrogen bubble that had formed within the reactor vessel, which experts worried could explode, though this fear was later allayed.

Extensive studies in the decades following the accident have not found any discernible long-term health effects, such as increased cancer rates, in the local population due to the small amount of radiation released. The primary and most lasting impact of the Three Mile Island event was a significant blow to public trust in nuclear energy. The incident prompted sweeping changes in the nuclear power industry, leading to enhanced safety protocols, more rigorous operator training, and stricter regulatory oversight by the Nuclear Regulatory Commission.