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United States

Three Mile Island

Discover the fascinating history and gain a deeper understanding of the Three Mile Island Nuclear Power Plant and the 1979 partial nuclear meltdown of Unit 2

The Three Mile Island nuclear power plant holds the distinction of being the USA’s worst nuclear accident and a must see dark tourism destination. The site, perched on a sandbar on the Susquehanna River near Harrisburg, PA experienced a partial meltdown of Unit 2 caused by a perfect storm of operational, procedural and mechanical failures that would leave lasting effects on the surrounding communities.

In the early morning hours of March 28th, 1979 maintenance activities on Unit 2 caused the detection of a problem which led to the on-duty operators to override a safety system because of confusion of the readings on the dozens of gauges. The measurements inside the reactor showed there was too much pressure which led them to turn off the pumps that provide cooling to the reactor. Without water, the intense heat boiled the remaining water in the reactor, compounding the pressure inside the vessel. The system’s fail-safe P.O.R.V. (pilot-operated relief value) automatically opened to relieve the growing pressure inside the reactor.

The P.O.R.V. value opened without incident but failed to close once the pressure was relieved. There were no indicator lights in the control room showing the status of the P.O.R.V.; This allowed the reactor to continue to boil the remaining water and the high-pressure steam to be released into the atmosphere.

Engineers finally identified and resolved the stuck P.O.R.V. valve and why the indicates gauges were showing inaccurate data. The cooling pumps were turned on, slowly putting an end to the five-day crisis.

In the years and decades to follow, reports showed different environmental and health impacts from the release of radioactive substances during venting activities. Moreover, reports showed that the fledgling nuclear industry wasn’t as safe as many hoped it to be.

Intense public criticism of the disaster targeted Metropolitan Edison, the operator of the Three Mile Island nuclear plant for intentionally misleading the public and falsifying facts during the incident. The ambiguity between NRC and Met Ed officials was so bad that President Jimmy Carter had to step in to restore the public’s confidence.

The Three Mile Island nuclear power plant Unit 2 was severely damaged and was never returned to operation. It is still licensed for operation by the NRC but in a permanent shut down state. The reactor building and 30-story cooling towers still stand as a testament to the country’s worst nuclear accident.

Through the viewfinder

Three Mile Island Uncensored

Three Mile Island was considered a “near miss” in terms of a disaster, unlike the Chernobyl Nuclear Power Plant disaster just a few years after. There was a small amount of radioactivity released into the atmosphere, however nothing significant. The reactor is still in operator today and thus tours are not allowed for security reasons.

If you’re planning on visiting this site, be prepared to be underwhelmed. There’s one tree-lined road that runs parallel to the power plant. Thankfully, some genius got the idea of cut the trees near the memorial marker for the the disaster site – you can snap some decent pictures of the plant, but nothing cool.

Frequently Asked Questions

Can you visit or tour the Three Mile Island power plant?

No. Three Mile Island is a nuclear power plant and thus cannot be toured without prior authorization from the plant operator.

How close can you get to Three Mile Island?

There is a clearing on River Rd (PA 441) directly west of the power plant where the trees have been cleared. This is the closest public spot where you can see the Three Mile Island Nuclear Power Plant.

Is the Three Mile Island nuclear power plant still active?

TMI Unit 1 was permanently shut down on September 20, 2019. To date, 99% of the remaining fuel has been removed from the site.

Is Three Mile Island still radioactive?

During the events of 1979, a small amount of radiation was released into the atmosphere. Today, there are numerous monitoring stations adjacent to the facility and around the area which do not register any significant amounts of radioactivity.

Everything you need to know before you visit Three Mile Island


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