Beta 3 at Y-12

A multi-story red brick building with limited windows/doors
Beta-3 at Y-12 is where the well-known Calutron Girls worked.


Quick Facts
Oak Ridge, TN

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. 

In 1943, as the Y-12 Electromagnetic Isotope Separation Plant was being built, Secretary of War Henry Stimson made an astounding request. He asked Secretary of the Treasury Henry Morgenthau Jr. to supply 6,000 tons of silver for this new top-secret undertaking. Stimson wanted assurances that it would be discreetly supplied and discreetly returned at a later date. The Manhattan Project secured approximately 13,540 short tons (395 million troy ounces) of silver from federal government vaults at West Point, New York. It cost over $300 million in contemporary dollars, but a key component of the calutron magnets was now available.

Beta 3 (9204-3) continues to house the original calutron arrays, or beta “racetracks” used during the Manhattan Project era, operated in conjunction with the alpha racetracks at the neighboring Y-12 Pilot Plant . Also within Beta 3 are the original control rooms where workers including the cubicle operators known as the “Calutron Girls” operated the arrays, separating uranium isotopes with powerful electromagnets. These women helped provide enriched uranium-235 for use in Little Boy, the world’s first atomic bomb. The final product of enriched uranium used in Little Boy came from these beta racetracks. By the end of 1946, all nine alpha racetracks and six beta racetracks had ceased operation, as the gaseous diffusion method used by nearby K-25 became the preferred uranium-enrichment method used throughout the Cold War.

Continue Your Journey

The Y-12 beta racetracks survive as the only production equipment from the electromagnetic isotope separation method. Y-12 is a highly-secured facility. Visitation is not permitted. However, the New Hope Visitor Center, open to the public, is located nearby. There you can learn more about Y-12's important roles from the Manhattan Project to the present day.


Manhattan Project National Historical Park

Last updated: August 31, 2023