8 Key Insights into the Three Mile Island Nuclear Incident

The year 1979 marked the closest the United States ever came to experiencing a full-scale commercial nuclear disaster.

A faulty valve caused a partial meltdown in one of the reactors at the Three Mile Island nuclear facility, situated on a small island in Lake Frederic, part of the Susquehanna River, approximately 10 miles downstream from Harrisburg, Pennsylvania's capital. Thankfully, a full-blown disaster was averted.

While the Three Mile Island incident has been eclipsed by the more catastrophic nuclear disasters at Chernobyl in 1986 and Fukushima in 2011, its impact has persisted for decades, influencing U.S. energy policies and leaving a mark on popular culture. A new four-part docuseries, *Meltdown: Three Mile Island*, is set to debut on Netflix on May 4, 2022.

With this context, here are some crucial details to understand about the Three Mile Island incident.

1. Three Mile Island housed two nuclear reactors.

Work on the first reactor at Three Mile Island, TMI-1, commenced on May 18, 1968—ten years after the launch of the Shippingport Atomic Power Station, America's inaugural commercial nuclear facility, located roughly 250 miles west of Three Mile Island in western Pennsylvania. The second reactor, TMI-2, began construction over a year later, on November 1, 1969.

TMI-1 became operational in 1974, while TMI-2 started functioning in 1978. Both were pressurized water reactors, utilizing feedwater pumps to circulate pressurized water to a steam generator, which served as the primary cooling mechanism. From its inception, the TMI-2 reactor, where the accident later occurred, faced issues. It experienced unplanned shutdowns due to leaks, and post-accident investigations uncovered that plant managers had intentionally manipulated data to maintain operations.

2. The crisis escalated in mere seconds.

Around 4 a.m. on March 28, 1979, a minor issue arose in the non-nuclear section of the plant when a feedwater pump failed to deliver water to the steam generator. This triggered an automatic shutdown of both the turbine generator and the TMI-2 reactor as a safety measure—a process that took just one second.

To manage the rising pressure and heat inside the reactor, a valve was opened to release steam and was supposed to close once the temperature stabilized. However, the valve remained open, even though control room instruments indicated it had closed. According to the United States Nuclear Regulatory Commission (USNRC), "the staff was unaware that steam was escaping through the stuck valve. Despite alarms and warning lights, operators failed to recognize the loss-of-coolant accident."

Additional water was pumped into the reactor, but due to the faulty instrumentation, no one realized the valve was still open, causing the water to escape. Consequently, the reactor overheated, and without sufficient coolant, the core suffered significant damage.

3. Later that same day, radioactive material was released into the atmosphere.

Contrary to common misconceptions, well-operated nuclear power plants emit minimal radiation (coal-based plants actually release about three times as much). As stated by the USNRC, "most direct radiation from a functioning nuclear plant is contained by its steel and concrete structures. The remaining radiation disperses within a controlled, uninhabited zone around the facility, ensuring no impact on the public."

Approximately 2 million people may have been exposed to elevated radiation levels due to the Three Mile Island incident. While children and pregnant women were advised to evacuate, around 140,000 individuals voluntarily left the area. An 18-year study of residents within a 5-mile radius—totaling about 150,000 people—found no significant rise in mortality linked to the accident, though it noted an increased risk for certain cancers.

4. The Three Mile Island accident happened less than two months after Pennsylvania's newly elected Governor, Dick Thornburgh, took office.

Thornburgh, a Pittsburgh native who had previously run for the U.S. House and served as U.S. Attorney for Western Pennsylvania, earning recognition for prosecuting organized crime, was elected governor in 1978. Just 72 days into his term, the crisis unfolded. Alongside President Jimmy Carter, he visited the site, and his calm leadership—avoiding a mass evacuation and remaining in central Pennsylvania—earned him praise as the crisis's hero. After two terms as governor, Thornburgh became U.S. Attorney General under Ronald Reagan in 1988, serving until 1991 under George H.W. Bush. A dedicated public servant, Thornburgh passed away on December 31, 2020, at the age of 88.

5. The film *The China Syndrome*, which eerily predicted the disaster, was released less than two weeks before the Three Mile Island incident.

*The China Syndrome*—named after the dramatic notion that a complete meltdown could cause the nuclear core to penetrate the Earth's crust and reach China—featured Jane Fonda and Michael Douglas as a news team covering a reactor accident, with Jack Lemmon playing the plant's shift supervisor. John Taylor, a Westinghouse executive, described the film as "an overall character assassination of an entire industry," as reported by The New York Times.

6. There were no fatalities reported.

The Three Mile Island incident resulted in no direct human deaths, but it dealt a severe blow to the nuclear power sector. During the 1960s and 1970s, nuclear energy was the primary source of clean energy, and Westinghouse thrived on building nuclear plants. However, after the accident, ongoing projects encountered delays, and new orders vanished. Plans for 39 proposed plants were scrapped, paving the way for coal and gas to dominate, along with their environmental impacts.

7. The disaster significantly influenced Bruce Springsteen.

Among those deeply affected by the incident was Bruce Springsteen, who resided less than 100 miles from Three Mile Island. He penned a song titled “Roulette,” reflecting on the accident and the ongoing debate about whether nuclear energy's advantages justified its environmental and health risks. The song, which includes the line "I've got a house full of things that I can't touch," begins with the following lyrics:

"We left the toys out in the yard I took my wife and kids and I left my home unguarded We packed what we could into the car No one here knows how it started ..."

Although Springsteen recorded the song in 1979, it remained largely unreleased (though accessible through bootlegs, as Springsteen once noted) until its inclusion in his 1998 *Tracks* box set. He also joined Musicians United for Safe Energy (MUSE) and performed at their iconic “No Nukes” concert. While his rendition of the Detroit Medley appeared on the No Nukes album, Springsteen released his complete concert set in 2021.

8. The TMI-2 reactor was permanently shut down after the accident.

The 1979 damage proved irreversible. Decontaminating the reactor took 12 years, and it eventually became a grim tourist destination, similar to Chernobyl. TMI-1 remained operational until the plant's shutdown on September 20, 2019, driven more by financial challenges than concerns about nuclear energy.