Manhattan Project History

John R. Dunning - Columbia University

     Gaseous diffusion appeared more promising.  Based on the well-known principle that molecules of a lighter isotope would pass through a porous barrier more readily than those of a heavier isotope, this approach proposed to separate U235 by utilizing a series of repetitions through many "cascades".

     Theoretically, this method could achieve high concentrations of uranium 235 but, like the electromagnetic method, would be extremely costly.

     British researchers led the way on gaseous diffusion, with John Dunning at Columbia joining the effort in late 1940.

     The biggest obstacle was finding a suitable material for the "porous barrier" that was able to withstand the corrosive properties of the uranium gas.  The research done at Columbia University eventually led to the design and construction of the K-25 plant at Oak Ridge, Tennessee.

See: 'Enrichment of Uranium"

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