A set decoration

In one scene set the laboratory office, On the wall with the door, behind Gail's desk, there were a couple of framed photos.

The one on the right looked familiar to me. It showed a giant rectangular U-shaped builting seen from the air.

I thought it was a building at the Oak Ridge, Tennessee, Manhattan Project facility. So with a little research I found it was the mile-long K-25 building, used to produce enriched Uranium by gaseous diffusion.

"K-25 was the codename given by the Manhattan Project to the program to produce enriched uranium for atomic bombs using the gaseous diffusion method. Originally the codename for the product, over time it came to refer to the project, the production facility located at the Clinton Engineer Works in Oak Ridge, Tennessee, the main gaseous diffusion building, and ultimately the site. When it was built in 1944, the four-story K-25 gaseous diffusion plant was the world's largest building, comprising over 5,264,000 square feet (489,000 m2) of floor space and a volume of 97,500,000 cubic feet (2,760,000 m3)."

https://en.wikipedia.org/wiki/K-25

So it is a little surprising that only 12 years later by 1956 when the movie was filmed, photos of the building were already declassified and available to be used as set decoration.