MIDDLETOWN, PA – Even 40 years later, John Garver vividly remembers the metallic taste of the nation's worst commercial nuclear disaster.

An acrid odor permeated Harrisburg as he walked out of a restaurant in Pennsylvania's capital city the morning of March 28, 1979.

"We had this smell in the air, wondering what it was," recalled Garver, 80, now a retired salesman. "Well it didn't take us long to find out ... that the accident started."

Some 14 miles away, the "accident" was unfolding in Unit 2 at the Three Mile Island Nuclear Power Plant, triggering panic, confusion and, within days, an evacuation order.

The partial meltdown sparked national protests, prompted increased safety standards for the nuclear power industry, and largely stymied the industry's momentum for decades until recent alarm over climate change has made some begin to embrace expanding carbon-free nuclear power.

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At noon on Friday, the remaining reactor (Unit 1) generated its last kilowatt of energy and closed, a victim not of the anti-nuclear movement but rather of simple economics. Even though the plant is licensed to operate until 2034, Exelon Generation ceased operations after the state of Pennsylvania earlier this year refused to throw the company a financial lifeline that would have kept it open.

The plant's four cooling towers will remain part of the landscape for now, foreboding concrete tombstones that seem out of place in the bucolic Susquehanna Valley of central Pennsylvania.

While it may not produce power, Three Mile Island (TMI) will continue to generate memories, said local historian Erik Fasick.

“It shouldn't be forgotten," he said, the towers looming over his shoulder as he stood outside the plant's grounds along Route 441. "It's the most important event that’s occurred in this area since the Battle of Gettysburg in 1863.”

Nuclear energy comeback

The closure of Three Mile Island comes as nuclear power is getting a second look thanks to the devastating impact of climate change.

Nuclear is the largest single supplier of carbon-free energy in the nation, providing about 20% of U.S. energy. With environmental groups and Democratic lawmakers calling for ambitious deadlines to wean the country off fossil fuels that emit greenhouse gases, advocates say nuclear power is emerging as a necessary ingredient of any response plan.

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Some Democratic presidential candidates have touted the benefits of "next-generation" nuclear power – or at least said it's worthy of consideration – as they push for alternatives to coal, oil and gas.

"Right now, nuclear is more than 50% of our non-carbon causing energy," Sen. Cory Booker, D-N.J., told a CNN town hall on climate change earlier this month. "So people who think we can get there without nuclear being part of the blend just aren't looking at the facts."

But economic factors, mainly from the production of cheap natural gas and increasingly affordable renewable sources, are slowly driving nuclear power out of business. In addition, diminished demand has hurt profitability, as have rising costs to operate them, analysts say.

Go to the infographic:How America’s worst nuclear accident unfolded

TMI's shuttering means there will be 97 commercial reactors at 59 plants scattered across 30 states.

Only one new nuclear power plant has come online in the United States since 2010: The Watts Bar Unit 2 in Tennessee, according to the U.S. Energy Information Administration. Two more reactors are under construction in Georgia, according to the Nuclear Regulatory Commission (NRC).

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But six reactors at five plants have been mothballed since 2013, and several others are slated to close in the next few years if they do not receive new financial support, according to a report last year from the Union of Concerned Scientists.

A number of plants that were already in the pipeline prior to TMI's accident received licenses to operate after 1979. But plans for 39 others were canceled in the wake of the catastrophe, according to NRC documents, though factors such as high interest rates also contributed to the slowdown in new plants.

"Public confidence in nuclear energy, particularly in (the) USA, declined sharply following the Three Mile Island accident," according to the World Nuclear Association, a pro-industry group. "It was a major cause of the decline in nuclear construction through the 1980s and 1990s."

Eric Epstein, a Harrisburg resident who chairs the Three Mile Island Alert organization that has long called for the shutdown of the facility, agreed that the accident set the industry back decades.

"If there is a good thing that happened because of TMI, it’s that it has ignited a fierce debate on the viability of nuclear power being safe, reliable, economical," he said.

The accident

Construction of the plant along the Susquehanna River near Middletown began in 1968 with the first reactor going on line six years later. Unit 2 came on line in December 1978, less than three months before its accident. Both were operated at the time by Metropolitan Edison. (Exelon, the current owner, didn't take over TMI until 2000).

At around 4 a.m. on Wednesday March 28, 1979, a mechanical or electrical failure prevented two pumps from sending water to steam generators, which cool the nuclear reactor with circulating water. A chain of events, punctuated by a stuck valve at the top of the pressurizer that was not detected, led confused operators to take steps that exposed the core leading to a partial meltdown.

A chemical reaction formed a bubble of hydrogen gas inside the reactor. Operators reduce the bubble’s size through periodic venting to the atmosphere through April 1. The plant entered a “cold shutdown” on April 27.

Over the next several days, there were conflicting messages about the severity of the crisis and how much radiation had been released.

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Geiger counters to detect and measure ionizing radiation became commonplace. Children and pregnant women were encouraged to evacuate the area, first within a five-mile radius of TMI, then within 20 miles. An estimated 140,000 residents left as well, hoping to outrun the radiation threat. President Jimmy Carter and wife Rosalynn visited Middletown the Sunday after the accident in a bid to calm anxious residents and a worried nation.

Fueling those fears was the release 12 days earlier of "The China Syndrome," a Hollywood thriller starring Jane Fonda about an accident at a nuclear power plant that was eerily similar to the scenario that unfolded at Three Mile Island, named because it sits three miles downriver from the center of Middletown.

In the movie, Fonda who plays a TV reporter is told that an explosion at the fictional plant located in Southern California “could render an area the size of the state of Pennsylvania permanently uninhabitable."

"I knew that line was coming ... Everybody knew it was coming," recalled Fasick, who as a seven-year-old accompanied his parents to watch the movie at a local theater a week after the accident. "When it was said, there was still that audible gasp. You could hear it."

The shuttered power plant became a popular stop for "dark tourism," the name given to infamous sites associated with death or tragedy that draw the morbidly curious.

Unit 2, a structure built to withstand an airplane crash, never reopened thanks to the malfunction of a tiny valve. Unit 1 returned to service in October 1985 under new management (GPU Nuclear Corporation) following the U.S. Supreme Court's decision not to block the restarting.

The accident forced drastic changes in nuclear power plant operations and safety measures. More stringent training procedures were adopted. Plants were upgraded to be more secure. Communication protocols between plant operators and area governments improved. More comprehensive warning and preparation regimens were adopted. Evacuation plans grew more sophisticated.

There has been no major problem at a U.S. nuclear plant since Three Mile Island.

'I'm not going to leave'

Founded in 1755 about 50 miles north of Baltimore, Middletown is a central Pennsylvania hamlet steeped in history.

William Penn chose the site for a settlement in 1690. George Washington visited in 1774. A tunnel recently unearthed under an abandoned house is believed to be a stop on the underground railroad used to ferry slaves from the South to free states.

As time passed, many of the Scots and Irish who helped settle the area moved on, giving way to a wave of German immigrants who planted roots in the rolling hills and fertile farmland during the 19th Century.

All of that history is now overshadowed by the "accident."

Many left the area as the warnings about the danger grew louder. Most returned after a few days when radiation levels were deemed not as harmful as first feared.

Numerous studies conducted over the years to determine whether radiation from the accident elevated cancer rates have been inconclusive.

Fasick, the historian who was a first-grader in nearby Lemoyne when it happened, believes the character of the area's residents contributed to their refusal to relocate.

“I remember my parents talking about it. My father said we’re not going anywhere. I think it was the sentiment of a lot of people. Most of the people I knew and went to school with, no one left," he said. "I think it’s the Pennsylvania Dutch mentality of stubbornness. 'This is where I'm from and I'm not going to leave.'"

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Epstein, the anti-nuclear activist, was attending college in California at the time and had no plans to return to Harrisburg where his family ran a furniture store. Then Three Mile Island happened and he grew "parochial and defensive" upon hearing the countless insults hurled at his beloved community.

“I got tired of the (Saturday Night Live) skits," he said. "I grew up being proud of where I was from because we were known for three things: Hershey chocolate, the Amish in Lancaster, and Gettysburg. We were within an hour of losing all of that. We were a place you wanted to come. All of a sudden we were a place you wanted to avoid. Its’s what I came back to fight for.”

The challenge of nuclear waste

Three Mile Island is closing but it will be decades before it's dismantled.

The first step to decommissioning the site involves transferring fuel to dry cask storage, made of stainless steel and concrete, for secure containment. That should happen around 2022, according to a timeline provided by Exelon.

The disassembling of the plant's largest components, such as the cooling towers, are not expected to happen until 2074. Four years after that, all radioactive material will be safely stored or removed from station.

Epstein calls the on-site storage of waste “a toxic problem without a forwarding address.” It's an issue bedeviling the nuclear power industry.

Spent nuclear fuel is now being stored in pools or in concrete and dry casks at every operating reactor site around the country, as well as the sites of permanently shut down reactors, according to the Nuclear Regulatory Commission. All those sites have, and will continue to have, adequate storage for their spent fuel, an agency spokesman said.

In 1987, Congress selected Nevada's Yucca Mountain, a remote section of the Mojave Desert that sits about 90 miles northwest of Las Vegas, to become the nation’s permanent repository for nuclear waste generated by utility power plants and the military.

The Energy Department began pursuing a license for the facility in 2008. But the Obama administration abandoned the project three years later amid intense opposition from residents and political leaders in Nevada, including Harry Reid, who at the time was the Senate’s top Democrat.

With Reid gone, Congress keeps trying to revive the Yucca proposal.

The House last year voted overwhelmingly to direct the Department of Energy to resume the licensing process for a nuclear waste facility at Yucca. But the plan has stalled, prompting alternatives that would be more carrot than stick, such as a proposal to pay every Nevada resident an annual fee to take it.

Embracing an identity

About 515 workers now work at the plant, down from a peak of more than 700 over the past two decades. The workforce will gradually drop to about 50 by 2022.

The loss of hundreds of jobs adds to the complicated relationship the surrounding area has with Three Mile Island.

It's been an economic engine even as it carried the stigma of what its detractors call the "incident" implying that the partial meltdown was a human-caused accident that should have been avoided.

"When (Metropolitan Edison) told us they were going to build a plant, they met with us and told us all the good things ... 'You have nothing to worry about,'" said Garver, the Middletown retiree as he stood on a dock at the Tri-County Boat Club about a quarter mile from the plant's entrance. "They probably were right if they woulda ran it right.”

Garver, like many others in town, is glad the facility is shutting down but he also knows friends whose families have TMI workers facing a job loss or having to relocate to another Exelon plant in the state.

The closing remains a sensitive topic for many in Middletown even as some in the community embrace its connection to Three Mile Island.

The Nuclear Bean, a coffee shop, sells TMI-themed merchandise alongside gourmet teas. A new playground being planned for Hoffer Park will include locally themed features, including replicas of TMI's cooling towers. The local library has become a repository of Three Mile Island documents and records, a collection that drew visits from Japanese media following the 2011 earthquake that severely damaged Japan's Fukushima nuclear power plant.

Aside from the jobs TMI provides, Exelon officials say the company has been a solid corporate citizen by contributing $6 million to local charitable and other non-profit organizations as well as the 40,000 hours its employees have logged volunteering in the community.

John Ziats, 66, a retired state purchasing officer who volunteers at the Middletown Public Library, said contributions from Exelon have helped keep the doors open and the shelves stocked. With TMI closing, he worries how the library will make up for the loss of those corporate donations.

'People didn't even want to be around us'

Ziats was 26 when the accident happened. He remembers the same metallic taste Garver experienced and thought he was coming down with an illness until he learned of the partial meltdown.

At the urging of his cousins in Connecticut, he evacuated to New England. The traffic got worse the closer he got to New York as if everyone was fleeing Pennsylvania, he recalled. His sister saw people carrying birds and other animals, presumably to detect radiation that humans could not taste or smell. The lack of credible information only added to the overall anxiety.

When Ziats arrived in Connecticut and went to local drug store, he realized how much the accident had jarred the nation.

"People didn’t even want to be around us. (They) would step back because they were just fearful that we had some sort of contamination or something. So you kind of lived with that for a while," Ziats recalled as he sat in the library. "At the time, people were just so panicked."

He returned home a few days later when it looked safe. But his angst persisted and he attended an anti-nuclear protest near Harrisburg that featured Fonda.

But over time, Ziat's attitude changed.

He began to see carbon-free nuclear energy as an answer to the fossil fuels that contribute to global warming. He saw how TMI has played an important – and accident-free –role in his community over the past 40 years. And, following the discovery of a malignant tumor behind his left eye a few years ago, he saw how radiation treatments saved his life.

"How can you really be against the nuclear industry when they've done so many positive things for people," he said.

Garver, on the other hand, said he's relieved to see the plant close.

"You don't have to worry about it anymore. You don’t have to worry about sirens going off. You don’t have to worry about anything," he said, as the Susquehanna River lapped against the boat dock, the imposing towers looming behind him.

Garver said he never thought about leaving the area when the accident happened or when the remaining reactor started up again in 1985.

“This is my home," he said. "This is where I was born and this is where I’m going to die."

Then he added with a laugh: “Hopefully not from nuclear power. And I think I’m going to make it now.”