The sealing performance of bentonite/crushed basalt borehole plugs
Mixtures of crushed rock and bentonite are considered for backfilling and sealing high-level nuclear waste repositories. Many variables affect the hydraulic conductivity of such mixtures, including the size and shape of the rock particles, method of mixing and emplacement, water content and density of the clay, and the weight ratio of rock to clay. Mixtures of crushed basalt and bentonite have been tested in two types of permeameters, 20 cm diameter stainless steel permeameters and 10 cm diameter PVC permeameters. Plugs were installed as a single lift or in many lifts; the water content of the clay ranged from air-dry to as high as 200%. Preliminary results show that a mixture of 75% crushed basalt and 25% bentonite has a hydraulic conductivity between 1 x 10/sup -9/ cm/s and 2.5 x 10/sup -8/ cm/s. In some cases, preferential flow paths have developed (possibly as a result of the montmorillonite washing out of the crushed rock matrix), giving hydraulic conductivities as high as 1 x 10/sup -4/ cm/s. Other ratios of rock to clay have similar bimodal results. The probability of failure is decreased by including a higher percentage of clay in the plug, crushing the rock finer, and evenly mixing the crushed rock and clay. 136 refs., 50 figs., 7 tabs.
- Research Organization:
- Arizona Univ., Tucson (USA). Dept. of Mining and Geological Engineering
- OSTI ID:
- 5749828
- Report Number(s):
- NUREG/CR-4983; ON: TI88900188
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
053000 -- Nuclear Fuels-- Environmental Aspects
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
510300 -- Environment
Terrestrial-- Radioactive Materials Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
BASALT
BENTONITE
BOREHOLES
CAVITIES
CLAYS
COMPARATIVE EVALUATIONS
DATA
DATA COMPILATION
HIGH-LEVEL RADIOACTIVE WASTES
HYDROLOGY
IGNEOUS ROCKS
INFORMATION
MANAGEMENT
MATERIALS
MATHEMATICAL MODELS
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
ROCKS
SEALING MATERIALS
UNDERGROUND DISPOSAL
VOLCANIC ROCKS
WASTE DISPOSAL
WASTE MANAGEMENT
WASTES