SITE CHARACTERIZATION TECHNIQUES USING FRACTURE MINERALS FOR RADIOACTIVE WASTE DISPOSAL

Fractures in crystalline rock environments are important in radioactive waste disposal because they are the dominant pathways for radionuclide migration. Fracture minerals are of interest for determining the long-term stability of a repository site for disposal because they record paleo-fluid chemistry. In this study stable isotope analyses (δ¹³C and δ¹⁸O) were conducted on calcite samples, one of the dominant fracture filling minerals found in the Canadian Shield, obtained from boreholes drilled at the Lupin mine site in Nunavit, Canada. Measured δ¹³C and δ¹⁸O signatures ranged between –25.13 to + 29.53 ‰ PDB and –37.84 to –5.5‰ PDB, respectively. These values exceed the normal calcite geochemistry range that one would typically expect in a Shield environment (δ¹³C –20 to +10‰, δ¹⁸O –30 to –4‰ PDB). The δ¹³C values are among the heaviest recorded, suggesting a possible hydrothermal origin. The fluid inclusion experiments were conducted to determine the origin of water from which the calcite precipitated. Chemical analyses of crushed and leached rock samples coupled with the isotopic results, aid in determining paleo-hydrogeological processes that have occurred within this site, ultimately assessing rock performance for the long-term suitability for radioactive waste disposal.