Results are presented from investigations into the solubilities, sorption and migration behaviour of Agi. CsNO3, Na2U2O7. NpO2hOH and Pu(OH)4 in the near-field environment of an ILW repository located in a salt dome. Emphasis is placed on the synthetic complexing organics DBP, TBP, EDTA, citrate and oxalate, which influence the leaching and retardation of the above elements. Leachate data from real ILW forms, obtained from saturated salt solutions, have been compared with the results of the synthetic systems described.