Bill Wilcox, a former chemist at Y-12, recalls his days working at the plant.
Y-12 National Security Complex is celebrating 70 years. The U.S. Government broke ground on what would become Y-12 on Feb. 18, 1943.
At the time, it did not make headlines because it was a top secret project.
Since then, its role has changed from helping develop the first atomic bomb used in warfare to now taking apart weapons they once helped create.
"We've made an attempt to take our history our heritage and to put it out where the public knows more about Y-12. So it's beginning to change," said Ray Smith, Y-12 historian.
Y-12 began as part of the Manhattan Project during World War II. Y-12 employees separated the uranium needed for the atomic bomb known as "Little Boy."
Bill Wilcox worked as a chemist at Y-12 after it opened in 1943.
"I didn't have any idea what was going on. At Y-12 the dirty stuff came in the door of the lab I worked in and we made it clean going out," Wilcox recalled.
That changed on Aug. 6, 1945 when "Little Boy," the first atomic bomb used in warfare, fell on Hiroshima.
"My boss' secretary came rushing across the hall and said, 'They've dropped an atomic bomb on Japan' and all of a sudden it came across that, so that's what we were doing,"
Three days later, a second atomic bomb dropped on Nagasaki.
Japan surrendered on Sept. 2, 1945.
"End of the war that we had worked so hard for and prayed so long for, finally over. A war that had killed 54 million people, killed by other human beings... 54 million," Wilcox said.
With the end of the war, came the end of Y-12's first mission.
The plant downsized from 22,000 employees to 3,000. But Y-12 continued to thrive, working for NASA and manufacturing components for U.S. nuclear weapons during the Cold War.
Y-12's mission shifted again in the '90s. It now disassembles nuclear weapons and still houses the nation's stockpile of uranium.
Those against nuclear warfare continue to protest at Y-12.
On July 28, 2012 it reached a new level when three protestors made it behind the fences of Y-12, all the way to the Highly Enriched Uranium Facility.
"The fact that they got to the point that they did was very embarrassing and has turned out to be a major review of all security practices not just here at Y-12 but across the complex," Smith said.
Y-12 has also had to review its plan for a new multi-billion dollar Uranium Processing Facility.
Last year, the Defense Nuclear Facilities Safety Board found several design issues.
Now, construction is set to start later this year.
"Some of the uranium processing facilities that we use today were built in 1945. So they're very old and we've had to repurpose them over the years and they're expensive to maintain," Smith explained.
The Uranium Processing Facility is estimated to cost up to $6.5 billion and could start operating in 10 years.