On March 30, 1979, one of the worst nuclear accidents in history occurred at the Three Mile Island power plant located in Pennsylvania, USA. During a routine test, a failure in the non-nuclear secondary system caused a buildup of steam pressure in the reactor vessel. This led to a partial meltdown of the nuclear fuel rods.
The incident released a significant amount of radioactive gases and iodine-131 into the environment, but the primary containment structure prevented a complete release of the radioactive material. However, the incident triggered the evacuation of over 140,000 people from the surrounding area as a precautionary measure.
The Three Mile Island accident led to widespread public fear of nuclear power and resulted in increased regulatory oversight and safety measures being put in place in the nuclear power industry. It is estimated that the long-term health effects on the population were minimal, but the incident remains a significant event in the history of nuclear power.