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National Museum of Nuclear Science & History

K-25 Plant

The K-25 Plant in Oak Ridge used the gaseous diffusion process to enrich uranium.

Gaseous Diffusion Process

The K-25 plant was an enormously ambitious and risky undertaking. A mile-long, U-shaped building, the K-25 plant was the world’s largest roofed building at the time. British scientists working on the “tube alloy,” code for the atomic bomb project, first advocated the gaseous diffusion method in March 1941.  Because of the Nazi bombing of England, any production plants had to be located elsewhere.

Columbia University’s John R. Dunning and Eugene Booth began working in 1941 on the gaseous diffusion process. The goal was to separate the isotopes of U-235 from U-238 by turning uranium metal into uranium hexaflouride gas and pumping it through a barrier material that had millions of microscopic holes.

Developing an effective barrier material was the greatest challenge. Columbia University’s SAM Labs, Kellex, and Union Carbide all pursued major programs addressing this very difficult problem, and all contributed to its final solution.  General Groves ordered construction to begin and the plant was one-third complete before a solution was found.

Building a Mile-Long Plant

K-25 cost $512 million to build, or $6.5 billion in 2010 dollars. The mile-long, U-shaped plant covered forty-four acres, was four stories high and up to 400 feet wide. Engineers developed special coatings for the hundreds of miles of pipes and equipment to withstand the corrosive uranium hexaflouride gas that would pass through the plant’s 3,000 repetitive diffusion stages (together making up a cascade).  

The entire process was hermetically sealed like a thermos bottle, as any moisture could cause a violent reaction with the uranium hexafluoride.  Even minute pinhole leaks and contamination from fingerprints were major concerns. A special leak detector was invented and every component of the entire system underwent a “cleanliness control” procedure before it was installed.  

After the War

The K-25 plant was more reliable and efficient than anyone predicted. After the war, the K-25 was expanded with the K-27, K-29, K-31 and K-33 plants built as additional stages of the process.  The plants produced the majority of the U-235 for the Cold War arsenal. The K-25 plant was the first large-scale fully automated factory in history.  Because of the complexity and size of the plant, 9,000 employees working in three shifts were needed to monitor its operations.  

Until 1985, K-25 produced fuel for civilian nuclear power reactors around the world.  In addition, K-25 developed a commercially competitive gas centrifuge technology.  K-25’s innovative technologies served the nation in World War II and the Cold War with great distinction. 

Oak Ridge Turnpike Oak Ridge TN, 37830 US
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