Rapid increases in permeability and porosity of bentonite-sand mixtures due to alteration by water vapor

Conference · Sun Jan 01 00:00:00 EST 1984

OSTI ID:6323040

Couture, R A

Packed columns of canister packing material containing 25% bentonite and 75% quartz or basalt sand, were exposed to water vapor at temperatures up t 260/sup 0/C. The permeabilities of the columns were subsequently measured after complete saturation with liquid water in a pressurized system. Exposure to water vapor caused irreversible increases in permeability by factors of up to 10/sup 5/. After saturation with liquid water, the permeability was nearly independent of temperature. The increases in permeability were due to a large decrease in the ability of the bentonite to swell in water. Calculations suggest that swelling of bentonite altered at 250/sup 0/C was not sufficient to fill the pore spaces. If the pore spaces are filled, the mixture will form an effective barrier against flow, diffusion, and transport of colloids. The results suggest that if bentonite-based canister packing material is exposed even briefly to water vapor at high temperatures in a high-level nuclear waste repository, its performance will be seriously impaired. The problem is less severe if the proportion of bentonite is high and the material is highly compacted. Previous results show significant degradation of bentonite by water vapor at temperatures as low as 150/sup 0/C. This suggests that in some repositories, backfill in tunnels and drifts may also be affected. 9 references, 5 figures, 1 table.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31-109-ENG-38
• OSTI ID: 6323040
• Report Number(s): CONF-841157-18; ON: DE85001841
• Resource Relation: Conference: Symposium on the scientific basis for nuclear waste management, Boston, MA, USA, 26 Nov 1984; Other Information: Paper copy only, copy does not permit microfiche production
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
BENTONITE
PERMEABILITY
POROSITY
SAND
BACKFILLING
BASALT
EXPERIMENTAL DATA
HIGH TEMPERATURE
HIGH-LEVEL RADIOACTIVE WASTES
MIXTURES
PERFORMANCE
TEMPERATURE EFFECTS
WATER VAPOR
CLAYS
DATA
DISPERSIONS
FLUIDS
GASES
IGNEOUS ROCKS
INFORMATION
MATERIALS
NUMERICAL DATA
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
ROCKS
VAPORS
VOLCANIC ROCKS
WASTES
360603* - Materials- Properties
052002 - Nuclear Fuels- Waste Disposal & Storage