K-25 Big Portal/Checkpoint

The K-25 Big Portal was one of several checking stations within the K-25 complex.

NPS/BURGHART

Quick Facts

Location:

Oak Ridge, TN

MANAGED BY:

Department of Energy

The sheer size of the K-25 Gaseous Diffusion Plant and the number of workers required to operate it, necessitated a facility to securely check in and out workers for their various shifts.

The K-25 Big Portal/Checkpoint housed guards who screened the thousands of employees that entered and exited the uranium enrichment facility every day. This portal, one of over a dozen, operated from the Manhattan Project through the Cold War. The continued operation of K-25 allowed the United States to keep using the gaseous diffusion method as the country developed more and more atomic weapons.

Continue Your Journey

The K-25 Big Portal/Checkpoint, along with the neighboring Small Portal, are the only two checking stations left at the K-25 site. After K-25 ceased operations in 1987, US Department of Energy contractors demolished the other 12 portals, leaving only these two to bear witness to decades of revolutionary science at this massive facility. For more information on the history of the K-25 complex from the Manhattan Project to the present day, please visit the K-25 History Center.