Some characteristics of potential backfill materials
A backfill material is one of the multiple barriers that may be involved in the disposal of nuclear waste. Such backfill should be a desiccant with the hydrous product having acceptable stability; it should sorb any released radioisotopes, and it should reseal any breached site. The backfill must also have acceptable thermal conductivity. This report presents data on the rate of hydration and the nature of the product of reaction of some candidate backfill materials with water and with brine. Thermal conductivity data is reported for both the reactants and the products. Granular MgO at 150/sup 0/C completely hydrates in less than 10 hours. At 60/sup 0/C and 20/sup 0/C, such extensive hydration requires about 100 and 1000 hours, respectively. The product of the reaction is stable to more than 300/sup 0/C. A doped discalcium silicate was less reactive and the product contains less water of crystallization than the MgO. The reaction product of dicalcium silicate is cementous, but it has low thermal stability. Bentonite readily reacts with water and expands. The reaction product has the properties of vermiculite, which indicates that magnesium ions have diffused into the bentonite structure and are not simply adsorbed on the surface. If bentonite is emplaced in a saline environment, the properties of vermiculite, the reaction product, should also be considered. The thermal conductivity of MgO, discalcium silicate, and bentonite is primarily dependent on the porosity of the sample. A slight increase in thermal conductivity was found with increased temperature, in contrast to most rocks. If the conductive data for the different materials is equated to the same porosity, MgO has the superior thermal conductivity compared to bentonite or discalcium silicate.
- Research Organization:
- Lehigh Univ., Bethlehem, PA (USA)
- DOE Contract Number:
- AC06-76RL01830; AC02-83CH10140
- OSTI ID:
- 6105653
- Report Number(s):
- ONWI-449; ON: DE83014668
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
BACKFILLING
MATERIALS TESTING
BENTONITE
HYDRATION
THERMAL CONDUCTIVITY
CALCIUM SILICATES
MAGNESIUM OXIDES
RADIOACTIVE WASTE DISPOSAL
DOPED MATERIALS
POROSITY
SORPTIVE PROPERTIES
VERMICULITE
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CALCIUM COMPOUNDS
CHALCOGENIDES
CLAYS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
IRON COMPOUNDS
IRON SILICATES
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
MANAGEMENT
MATERIALS
MICA
MINERALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SOLVATION
SURFACE PROPERTIES
TESTING
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
WASTE DISPOSAL
WASTE MANAGEMENT
052002* - Nuclear Fuels- Waste Disposal & Storage
360603 - Materials- Properties