Thermal-gradient migration of brine inclusions in salt crystals. [Synthetic single crystals of NaCl and KCl]

Technical Report · Wed Sep 01 04:00:00 EDT 1982

DOI:https://doi.org/10.2172/6679490· OSTI ID:6679490

Yagnik, S K

It has been proposed that high-level nuclear waste be disposed in a geologic repository. Natural-salt deposits, which are being considered for this purpose, contain a small volume fraction of water in the form of brine inclusions distributed throughout the salt. Radioactive-decay heating of the nuclear wastes will impose a temperature gradient on the surrounding salt which mobilizes the brine inclusions. Inclusions filled completely with brine migrate up the temperature gradient and eventually accumulate brine near the buried waste forms. The brine may slowly corrode or degrade the waste forms which is undesirable. In this work, thermal gradient migration of both all-liquid and gas-liquid inclusions was experimentally studied in synthetic single crystals of NaCl and KCl using a hot-stage attachment to an optical microscope which was capable of imposing temperature gradients and axial compressive loads on the crystals. The migration velocities of the inclusions were found to be dependent on temperature, temperature gradient, and inclusion shape and size. The velocities were also dictated by the interfacial mass transfer resistance at brine/solid interface. This interfacial resistance depends on the dislocation density in the crystal, which in turn, depends on the axial compressive loading of the crystal. At low axial loads, the dependence between the velocity and temperature gradient is non-linear.At high axial loads, however, the interfacial resistance is reduced and the migration velocity depends linearly on the temperature gradient. All-liquid inclusions filled with mixed brines were also studied. For gas-liquid inclusions, three different gas phases (helium, air and argon) were compared. Migration studies were also conducted on single crystallites of natural salt as well as in polycrystalline natural salt samples. The behavior of the inclusions at large angle grain boundaries was observed. 35 figures, 3 tables.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6679490
• Report Number(s): LBL-14752; ON: DE83004180
• Country of Publication: United States
• Language: English

Related Subjects

052002* -- Nuclear Fuels-- Waste Disposal & Storage
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
AIR
ALKALI METAL COMPOUNDS
ARGON
BENCH-SCALE EXPERIMENTS
BRINES
CHLORIDES
CHLORINE COMPOUNDS
CRYSTAL STRUCTURE
DATA
ELEMENTS
EXPERIMENTAL DATA
FLUIDS
GASES
GEOLOGIC DEPOSITS
GRAIN BOUNDARIES
HALIDES
HALOGEN COMPOUNDS
HELIUM
INCLUSIONS
INFORMATION
LIQUIDS
MANAGEMENT
MASS TRANSFER
MATHEMATICAL MODELS
MICROSTRUCTURE
MIGRATION
NONMETALS
NUMERICAL DATA
POTASSIUM CHLORIDES
POTASSIUM COMPOUNDS
RADIOACTIVE WASTE DISPOSAL
RARE GASES
SALT DEPOSITS
SALTS
SODIUM CHLORIDES
SODIUM COMPOUNDS
TEMPERATURE GRADIENTS
UNDERGROUND DISPOSAL
VELOCITY
WASTE DISPOSAL
WASTE MANAGEMENT