DAUPHIN COUNTY, Pa. -- It's the 40th Anniversary of the Three Mile Island Nuclear Power Plant partial meltdown in Dauphin County.
The meltdown at TMI is the most serious accident in United States commercial nuclear power plant operating history.
Nuclear officials say what happened 40 years ago forever impacted the nuclear industry.
Three Mile Island Nuclear Power Plant made front-page news all across the world when its unit 2 reactor partially melted down and released dangerous radioactive gases into the atmosphere.
One nuclear engineer hesitates to call it an accident.
“Calling it an accident is sort of like when a deer hits your car or owl flies into your windshield - it can’t be predicted," said Arnie Gundersen, who has four decades experience in the nuclear field. “TMI had predecessors. There were things that happened in the year or two running up to TMI that were close calls, and it’s interesting because a guy at the Nuclear Regulatory Commission brought it to the commissioners attention five days before the meltdown - they didn’t have time to take a hard look.”
Gundersen adds officials also failed to look at the training needed to safely operate a plant.
“TMI had a group of smart guys, nice guys, but they were in over their heads because they were never trained on what would happen if the thing went off the rails," explained Gunderson.
“They weren’t prepared for worst case scenario?" asked FOX43.
“I have a saying, ‘sooner or later in any full-proof system, the fools are going to exceed the proofs', and that’s what happened," responded Gunderson.
In its aftermath, he said there were three big changes - the biggest concerned those operators.
“The operators at TMI were trained, but they were trained in what was the normal operation of the plant. Now, trainer is broader. It goes outside normal so they can react to situations quicker," said Gundersen.
The next thing? A new global exchange of information.
“Now, the nuclear industry shares data," explained Gundersen. "If something happens at one site, the other sites learn about it. Back then, they didn’t learn about it.”
Last, Gundersen says more than 100 nuclear plants on the drawing board at the time were scratched.
Gundersen says his 40-year career is marked by 5 meltdowns, including the one at TMI, and claims more can be done in terms of prevention.
“By and large, they’re better. There’s still those things that are unanticipated. You just wonder when the next one will hit," he said.
People will gather at Three Mile Island for the annual vigil Thursday.
It begins at 3:15 a.m.