Y-12 National Security Complex

A modern, sunlit office complex with several flags flying in front
Y-12 continues to fill a vital national security role.


Quick Facts
Oak Ridge, TN

Scenic View/Photo Spot

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. 

At Oak Ridge, Tennessee, Manhattan Project administrators developed three massive facilities to separate and enrich uranium as fuel for an atomic bomb, a powerful and not fully realized technology. The Y-12 Electromagnetic Isotope Separation Plant, now named the Y-12 National Security Complex, was the first facility in Oak Ridge constructed solely for this purpose. 

The construction of the Y-12 Plant was founded on the need for a facility that could perform electromagnetic isotope separation. Developed by University of California at Berkeley scientist Ernest Lawrence, electromagnetic isotope separation was based on the concept that lighter uranium atoms (U235) would move more tightly in a circle than heavier uranium atoms (U238). The creation of a cyclotron, a vacuum tank with a strong magnetic field, could separate the atoms into two paths as they revolved. The lighter U235 was captured in a separate container from the heavier U238. Lawrence had created a mass spectrometer cyclotron, or calutron, at his Berkeley lab in late-1941, but Manhattan Project scientists determined  a much larger facility would be required to produce the separated U235 needed to develop an atomic bomb in a timely fashion. This necessitated construction of the much larger Y-12 Plant, which began on February 18, 1943. 
At its peak, the Y-12 Plant employed 22,000 people to operate the calutrons, nicknamed “racetracks” for their oval shape. While the facility at Berkeley had only been operated by scientists, a wartime labor shortage meant young women, many of whom had just graduated high school, were assigned the task of operating the calutrons at Oak Ridge. These women, nicknamed “Calutron Girls,” were vital to the development of enriched uranium, a key component of the Little Boy atomic bomb.

Continue Your Journey 

Y-12 is still in operation to this day, helping to ensure a safe and effective U.S. nuclear weapons deterrent. Y-12 also retrieves and stores nuclear materials, fuels the nation’s naval nuclear reactors, and performs complementary work for other government and private-sector entities. The Y-12 National Security Complex is a highly-secured facility. Unauthorized visitation is not permitted. However, a public museum, the New Hope Center at Y-12, is located nearby. There you can find information and exhibits on Y-12 from the Manhattan Project through the Cold War to the present day. 


Manhattan Project National Historical Park

Last updated: August 31, 2023