[en] Low- and intermediate level radioactive waste, produced at Swedish nuclear power plants, will be deposited in an underground repository, SFR. Different substances in the waste or in degradation products emanating from the waste, and chemicals added during the building of cementitious barriers in the repository, may exhibit complexing properties. The complexation of radionuclides with such ligands may increase the mobility of the deposited radionuclides as sorption on the cement phases is decreased and solubility increased. This could lead to an increased leaching of the radionuclides from the repository to the geosphere and biosphere. To be able to evaluate the implications for the function and long-term safety of the repository a study has been performed on complexants in SFR. The study is a part of project SAFE (Safety Assessment of Final Repository for operational Radioactive Waste) at the Swedish Nuclear Fuel and Waste Management Co, SKB. Concentrations of complexants were calculated in different waste types in the repository and compared to critical levels above which radionuclide sorption may be affected. The analysis is based on recent research presented in international and national literature sources. The waste in SFR that may act or give rise to substances with complexing properties mainly consists of cellulose materials, including cement additives used in waste conditioning and backfill grout. The radioactive waste also contains chemicals mainly used in decontamination processes at the nuclear power plants, e.g. EDTA, NTA, gluconate, citric acid and oxalic acid. The calculations performed in this report show that the presence of complexants in SFR may lead to a sorption reduction for some radionuclides in certain waste types. This may have to be considered when performing calculations of the radionuclide transport. Concentration calculations of isosaccharinic acid (ISA), using a degradation yield of 0.1 mole/kg cellulose (2%), showed that the limit above which effects on sorption of radionuclides is apparent (>10^-4 M) is exceeded mainly in three waste types in BMA (F.17, F.23/steel and S.21) and in one waste type in the Silo (S.22). The relatively high level of ISA is in part due to the fact that these waste types are not conditioned in cement (F.17 is bituminized), thus there is no sorption to cement. Both bi- tri- and tetravalent elements will probably be affected (S.21 and S.22). It should be pointed out that ISA will only be produced in these waste types if the integrity of the moulds is not maintained and alkaline water enters. Degradation of ISA has not been regarded in the calculations. Other conservative approaches have been adopted in the calculations, thus the concentration of ISA may be somewhat overestimated. Calculations assuming a higher yield of ISA, corresponding to 1000 years of degradation (about 2.5%), lead to relatively small changes in concentration. Calculations using a yet higher yield (10%), which corresponds to about 10 000 years of degradation, showed that critical levels of ISA may arise in all waste types. This is however a highly conservative approach. Due to the presence of NTA, citric acid, sodium capryl iminodipropionate and gluconate emanating from decontamination chemicals, critical concentrations may arise in some waste types in BMA, the Silo and BTF (e.g. F.17, B.05 and F.05). Elements probably to be affected is Mn and in some cases Ni and Pb. Na-gluconate may be present in such quantities that critical concentrations are obtained in waste packages containing unconditioned or bituminized waste (F.17, F.18, F.05 and O.07). Na-gluconate affects the sorption of Eu and potentially also other elements, but current knowledge is limited to Eu. For waste types where the waste is stabilised in cement, sorption of Na-gluconate on the cement will reduce the concentration below critical levels. EDTA will be present at relatively low concentrations but may exceed critical levels in a limited number (56) of waste packages of waste type S.09. The presence of cellulose based additives in cement used as backfill was evaluated. Calculations resulted in a concentration of ISA below critical levels. For the waste types in BLA the presence of complexing agents has not been studied as no credit is given in the safety assessment to sorption in this repository part (no cement/concrete). The performed calculations have shown that, due to the presence of ISA and other complexants in SFR, a reduction in sorption may have to be applied for some elements in certain waste types when carrying out calculations of the radionuclide transport (the number of waste types depends on assumptions regarding the ISA yield). It should be pointed out that the estimates of concentrations in different waste types are based on a number of conservative assumptions, thus the actual concentrations are probably lower than the calculated