Radionuclide Sorption on Drill Core Material from the Canadian Shield

The sorption of four radionuclides, ⁹⁰Sr, ¹³⁷Cs, ¹⁴⁴Ce, and ²³⁷Pu, on drill core material from two rock formations in the Canadian Shield has been studied as part of the Canadian Nuclear Fuel Waste Management Program. For all four radionuclides, sorption increased with increased mafic mineral content of the rock. Autoradiographic investigations showed enhanced sorption on dark, or mafic, minerals and high sorption on chlorite infilling material in a closed fracture. Desorption was less complete than sorption after the same equilibration time, indicating a degree of irreversible sorption, or slower desorption kinetics. The effect of surface roughness (measured by mercury porosimetry) on sorption was not as great as that of the chemical and mineral composition of the rock.