(WHTM) – Three Mile Island was the home of a nuclear power plant located in Londonderry Township, just south of Harrisburg on the Susquehanna River.

The plant opened in 1974, however, its time in operation was short-lived due to a cooling malfunction that resulted in a partial meltdown of the Unit Two reactor.

So how did this begin?

On the morning of March 28, 1979, the primary coolant’s temperature began to rise, which automatically turned the reactor off.

When this occurs, a pilot-operated relief valve opens and will remain open for 10 seconds. This is all part of the system but the valve didn’t close, which resulted in reactor coolant water being leaked into the reactor coolant drain tank.

However, the valve showed the operators that it was closed.

The next step was that water would be pushed into the reactor system but this forced the water levels to rise. Operators at Three Mile Island decided to reduce the water because if the pressurizer filled with water, the operators wouldn’t be able to control pressure in the cooling system, which could result in a rupture.

Although the workers believed they were helping the reactor they were actually worsening the problem.

With the lack of coolant and the reactor core not having the necessary water flow, the reactor core would overheat, causing the metal container to melt.

Half of the reactor core melted and a small amount of radioactive gas was released into the area.

This resulted in the public being concerned so the Pennsylvania Department of Health would have a registry of more than 30,000 people who lived within five miles of the island when the accident occurred. Results never showed anything unusual in health trends so the registry was shut down in 1997.

The Nuclear Regulatory Commission (NRC), the U.S. Department of Energy (DOE), the Environmental Protection Agency, the Department of Health, Education and Welfare (now Health and Human Services), and the Commonwealth of Pennsylvania all conducted a study and in the end, around two million people were exposed to the gas but zero health effects were detected.

The environment was also a concern but upon studies, it was determined that the radioactive gas didn’t affect the environment.

The island took years to clean up and would cost around $1 billion.

Unit Two was ultimately shut down but Unit One would continue operation until 2019.

Three Mile Island’s Unit One reactor was the longest operating run for any light water reactor in the history of nuclear power at 616 days and 23 hours.

Three Mile Island would also make an appearance in the song “Volcano” by Jimmy Buffet: “I don’t want want to land on no Three Mile Island.”