Experimental measurements were described on diffusivity and permeability of nulcear grade graphite. Nine carefully selected samples were progressively oxidised up to a maximum burn-off of 10 to 26%. It was shown that B0 and K0 (the permeability constants) and m (the ratio of diffusivity to free gas diffusivity) all increased steadily with increasing burn-off. At low percentage burn-off, the rate of increase of m was greater than that of the permeability constants. At 10 per cent burn-off, the increase in all the constants was approximately threefold. A simple model was devised which qualitatively explains the results obtained.

The Diffusion of Oxygen in Nitrogen in the Pores of Graphite: the Effect of Oxidation on Diffusivity and Permeability. Hewitt, G.F., Moore, M.J.C., Sharratt, E.W.: Carbon, 1970, 8[3], 271-82