WORKING K-25 
INTO THE MIX
Oak Ridge: Clinton (1943-1944)
Events: The Uranium Path to the Bomb, 1942-1944

In 1941 and 1942, gaseous diffusion had been considered by many as the most promising method of enriching uranium.  The British in the influential 1941 MAUD Report had advocated the use of gaseous diffusion alone, and the 1942 Lewis committee placed it first among isotope separation methods.  Despite the soundness of the theory, the process had yet to produce any samples of enriched uranium when the K-25 Gaseous Diffusion Plant was authorized in late 1942.

This disconnect between theory and practice carried over from the laboratory to the factory.  Even before construction began, it was decided in late summer 1943 that K-25 would not attempt to create weapons-grade uranium by itself.  Instead it would produce material that was about fifty percent uranium-235, which would then be fed into Y-12's Beta tracks (above) for final enrichment.  This would allow the elimination of the troublesome upper part of the cascade, but even fifty percent enrichment was not assured since a barrier for the diffusion plant still did not exist.  The decision to downgrade K-25 was part of the larger decision to double Y-12 capacity and fit with Groves's new strategy of utilizing a combination of methods to produce enough fissionable material for bombs as soon as possible.  

There was no doubt in Groves's mind that gaseous diffusion still had to be pursued vigorously.  Not only had major resources already been expended on the program, but there was also the possibility that it might yet prove successful.  Y-12 was in trouble as 1944 began, and the plutonium pile projects were just getting underway.  A workable barrier design might still put K-25 ahead in the race for the bomb.  Unfortunately, no one had been able to fabricate a barrier of sufficient quality; the uranium gas was simply too corrosive, the necessary tolerances too fine.  By the summer of 1944, the ongoing barrier crisis made it apparent that the material produced by K-25 would be of such low enrichment that it would first have to be run through Y-12's Alpha tracks before it would be ready for the Betas.  To accomplish even this low level of enrichment Groves had to order a crash barrier program.  The production of enough uranium-235 for even one bomb by 1945 now appeared to be very much in doubt.