160. Diffusion and migration of uranium in pyrolytic carbon

✍ Scribed by W.V Goeddel; H.K Lonsdale; N.L Sandefur

• Publisher: Elsevier Science
• Year: 1964
• Tongue: English
• Weight: 98 KB
• Volume: 1
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(64)90451-8

✦ Synopsis

Using U 232 as a tracer, self diffusion coefficients have been obtained as a function of temperature in three varieties of graphite. Measurements were made in the (c) and (a) directions in pyrographite, in 2.T.A.f (p=2.12) and a porous graphite (p== 1X1)1. The determinations spanned at least 400°C in all cases except pyrographite in the (c) direction. The results are summarized by the following equations: Dli,=27.,xexp(-117x 103/RT) Dl1~=6.7~x lO~xexp(-115/RT) DzTA=~.~ x 105x exp(-138.,x 103/RT) D,,,= 5.5 x 105x exp( -138., x 103/RT) Measurements made in well annealed pyrographite indicate a total absence of volume diffusion. It thus appears that all diffusion proceeds via lattice defects. The diffusion of U in Z.T.A. and ordinary porous graphite are indistinguishable.

It is therefore concluded that the diffusion proceeds solely via grain boundaries.

*Work was performed under the auspices of the U.S. Atomic Energy Commission.