The scientists and workers who were developing and producing "trigger devices" for atomic bombs were sworn to secrecy, subjected to lengthy background checks, spoke in code and practiced drills in the event of a Soviet attack on the plant.
Joe Garner of Farmersville worked at the Mound as a radiation safety officer from 1947 until he retired 41 years later. He worked in the T building, an underground facility fortified with 17-foot thick concrete walls that could withstand all but a direct hit from a nuclear bomb. The building had its own food and water supply that could sustain workers for months.
"We were definitely on the list," Garner recalled recently, referring to sites in the United States that would be likely targets in the event of missile attack by the Soviet Union, then locked in a stalemate of mutually assured destruction with the United States.
Garner said that periodically there would be simulated attacks, where the workers at the Mound would be shut inside T building to practice what to do.
"It was very real," he said. "We would be shut inside and there would be radio reports saying such and such has been hit. There were some people who couldn't take it. They would say they have to get out and go to their families."
Secrecy was also a requirement.
"You didn't talk about what you did in the lab," Garner said.
John Birden of West Carrollton, a research chemist on the atomic project from 1944 to 1981, said that workers would use code words when they had to refer to the radioactive material they used.
Garner said that the code name for polonium, which was used in the triggers to begin the neutron implosion that begins a nuclear reaction, was Postum, named after a substitute for coffee used during World War II.
When Birden joined the project, it was so secret they did not tell him what he was working on.
"I knew it was radioactive," he said. "But I did not learn what I was working on until I went back to an old college text and read some of the chapters we hadn't read in school. When I began to show some fundamental knowledge they said, `Ok, here's what we're working on.''
The scientists were also the subjects of FBI background checks.
"I remember one of my neighbors asking me what I was into," Garner recalled. "They said the FBI was here asking about you."
Security continued until the end of the Cold War.
"It actually increased in the 1980s, because of terrorism," said Bill Scuberling of Miamisburg, who was in security at the Mound from 1972 until 1980.