Measurements were reported of effective diffusivity of oxygen in nitrogen through the pores of various graphites with widely different permeabilities. The effect of back purging with nitrogen was studied. A thousand-fold reduction of apparent diffusivity occurred with back pressures ranging from about 3 to 720torr according to the type of graphite. The permeability constants (B0 and K0) were measured and introduced into a theoretical relationship which predicted the back diffusion data. The effect of pore structure on back diffusion and the application of the results to a type of high temperature, gas-cooled reactor were discussed.

The Effect of Back-Pressure on the Counter Diffusion of Gases in Graphite. Hewitt, G.F., Sharratt, E.W.: Journal of Nuclear Materials, 1964, 13[2], 197-206