Gas Permeability Studies on Some Artificial Graphites

Graphite matrix materials for nuclear waste isolation

“…The room-temperature permeability coefficients of a sample compacted to 1.96 Mg/m 3 were B = 0.45 x 10 14 cm 2 and K = 2.17 x 10 9 cm 2 • It appears that compacts o 0 could approach, or equal, the low permeability obtained after impregnations of EY-9 with furfuryl alcohol. (30,31) Other powders were annealed for 3 hours at 1000°C in a vacuum of 13 MPa (10-4 mm Hg), exposed to various atmospheres and then pressed at 230 MPa; Dag 621 powder when annealed, exposed (to argon, air, hydrogen, or water vapor), and pressed expanded to about 170% of its compressed height when the pressure was released (the lIas-receivedll Dag 621 expanded only 23%, and the resultant pellet had a density of 1.8 Mg/m 3 ); the 90 hour powder, annealed and exposed to air, expanded about the same as the annealed Dag 621 powder. A natural flake (annealed and exposed to air) expanded only about 8% and had a density of about 2.2 Mg/m 3 ; however, the compact was lIextremely friable ll compared to compacts prepared using unannealed flake.…”