In 1979 the Three Mile Island nuclear plant station had a potential leak. It was the most serious accident in American Nuclear power’s history.
The island is located on the Susquehanna River near the city of Harrisburg, PA.
The accident occurred at 4:00 AM on March 28, when an automatically operated valve in the Unit 2 reactor mistakenly closed, that shut off the water supply to the main feedwater system (the system that transfers heat from the water actually circulating in the reactor core). This action caused the reactor core to shut down automatically, but then a series of equipment and instrument malfunctions, along with human errors in operating procedures, and mistaken decisions in the ensuing hours led to a serious loss of water coolant from the reactor core. The result of these series of events would cause the core itself to be briefly exposed. The Ziconium cladding reacted to the superheated steam, causing a hydrogen gas that would marginally escape the core and filter into the plant itself. Thankfully, very little of this and other radioactive gases actually escaped into the atmosphere, and they did not constitute a threat to the health of the surrounding population. In the following days adequate coolant water circulation in the core was restored with no issues.
Though small in nature, this would cause a wave a change in how we saw Nuclear power. In fact 7 of the reactors at 3 Mile Island were quicky shutdown, but the shutdowns were temporary. However, the public’s negative views on it would cause a pause on American’s urge to invest in development of more Nuclear power plants down the line.