Intrinsic and carrier colloid-facilitated transport of lanthanides through discrete fractures in chalk

Geological disposal of spent fuel and high-level radioactive waste is the long term solution for the disposal of long lived radionuclides and spent fuel. However, some radionuclides might be released from these repositories into the subsurface as a result of leakage, which ultimately make their way into groundwater. Colloidal transport of radionuclides is considered one of the major pathways facilitating migration from the repository to the environment. Radionuclides leaked into the groundwater may precipitate, forming intrinsic colloids. ''Carrier'' colloids may also increase the mobility of radionuclides from the repository. Engineered bentonite barriers around nuclear waste repositories are considered sufficient to impede the transport of radionuclides to the groundwater. However, such barriers may decompose over time and release colloid-sized mobile bentonite particles that sorb radionuclides and carry them into the environment. Similarly, organic matter (e.g. humic and fulvic acids), present in many sedimentary rocks, may adsorb radionuclides and facilitate their transport. Such colloidal transport has come under investigation as a potential vector for radionuclides sorbed to them. As lanthanides are generally accepted as chemical simulants to the more toxic actinide counterparts, lanthanides are considered an acceptable substitute for research on radionuclide transportation. This study aims to evaluate the transport behaviors of lanthanides in colloid-facilitated transport through a fractured chalk matrix and under geochemical conditions representative the Negev desert, Israel