Sorption of nickel on geological materials

In CANDU (CANada Deuterium Uranium) fuel, 59Ni, with a half-life of 7.6x104, is produced by activation of Ni impurities in the UO2 fuel and in the Zircaloy cladding. Sorption data are sparse for this element on the solids of interest in the Canadian Nuclear Fuel Waste Management Program (CNFWMP). A 23 factorial experimental design was used to examine the effects of [Ca], [Mg] and pH on Ni sorption from solutions based on WN-1M, a reference synthetic groundwater widely used in the CNFWMP. Granite, biotite, K-feldspar, quartz, hematite and kaolinite were used as the solid phases. In general, sorption was greatest on hematite and least on quartz regardless of solution composition. Increased [Ca] and [Mg] and lower pH generally resulted in lower Ni sorption. The data indicated that Ni sorption may occur by a combination of ion exchange and surface complexation, depending on the nature of the sorbing solid. (orig.)