[en] The uptake of the long-lived radionuclides ${}^{226}$Ra and ${}^{99}$Tc, as well as iodide and molybdate ions by various model phases representative for phases present in hydrated cements was investigated. The model phases were synthesized under argon atmosphere, using well established procedures (e.g., Atkins et al., 1991 and 1992; Baur et al., 2004). Sorption and uptake kinetics by the model phases were studied in static batch experiments under anoxic conditions. Experiments performed for up to 60 days indicate a strong uptake of radium by calcite and CSH phases. Uptake studies performed on iodide revealed the incorporation into AFm-SO${}_4$. In contrast, no significant uptake of technetium, present as ${}^{99}$Tc(VII) in solution, by the various model phases was observed. Microanalytical investigations on the uptake of molybdate by AFm phases provided evidence of a molybdate substitution in AFm-SO${}_4$.