The transport or diffusion of uranium (as a stand-in for plutonium) was investigated under conditions approximating those of the primary coolant loop in a high-temperature gas-cooled reactor. Profiles were obtained for uranium penetration in H-451 graphite at 900 to 1400C. Expressions for profile data based on temperature and diffusion coefficients were developed.

Uranium Diffusion in H-451 Graphite. Tallent, O.K., Wichner, R.P., Towns, R.L.: Nuclear Technology, 1985, 68[3], 336-43