Y-12 Pilot Plant (Building 9731)

Building 9731 was the first to operate at Y-12.

DEPARTMENT OF ENERGY

Quick Facts

Location:

Oak Ridge, TN

OPEN TO PUBLIC:

No

MANAGED BY:

US Department of Energy

Amenities

1 listed

Historical/Interpretive Information/Exhibits

This building is within the highly secured Y-12 National Security Complex on US Department of Energy property and cannot be accessed by members of the public. 

Imagine being a young woman arriving for work on your first day at a top-secret facility, not knowing what your job would entail. Former “Calutron Girl” Gladys Owens remembers the warning from her new boss. “We can train you how to do what is needed, but cannot tell you what you are doing.” Her boss went on to say, “I can only tell you that if our enemies beat us to it, God have mercy on us!”  

Gladys’s day might have begun by slogging through the muddy, raw landscape of the new secret city and boarding a bus for a short commute with dozens of other young women from her dormitory. She would pass through security checkpoints to a massive facility where she performed work so secret that she could only guess at what she was doing and why she was doing it. This was the unique daily experience of the Calutron Girls of Oak Ridge. 

Building number 9731, known as the Y-12 Pilot Plant, houses the prototype equipment for the electromagnetic device known as Calutrons, an industrial-sized variety of mass spectrometer invented by University of California scientist Ernest Lawrence. The first building completed at Y-12 and the first to operate, building 9731 was the pilot building where operations workers and cubicle operators trained to perform uranium separation. Their work yielded enriched uranium 235 to fuel Little Boy, the world’s first uranium gun-type atomic bomb.  

The cubicle operators, known as the Calutron Girls, trained in building 9731 before operating the arrays at the larger production facilities at Y-12, including Beta 3. The calutrons in building 9731 remained in operation after the Manhattan Project and through a portion of the Cold War in order to continue producing radioactive isotopes for scientific research. Operations ended in 1970. Building 9731 houses the only remaining alpha calutron magnets from the Manhattan Project. 

Continue Your Journey

Y-12 is a highly-secured facility due to its continued top-secret national security functions. Unauthorized visitation is prohibited. However, you are welcome to visit Y-12's public New Hope Visitor Center to gain a deeper understanding of the Y-12 complex and its role during and after the Manhattan Project.