[en] A method for removing radioactive iodide by fixing onto an inorganic compound is described. The reactivity of BiPbO₂NO₃ with iodide was examined in a simulated low level radioactive liquid waste produced from a reprocessing plant, containing 26 components, among which NaNO₂, Na₂CO₃ and NaNO₃ are present in particularly high concentrations. The extent of the ion exchange reaction was examined at 25 degC and 50 degC as a function of time. The temperature dependence was very small and in a few hours, the concentration of free iodide ions was almost constant. The concentration change of unreacted iodide ions in solution was examined as a function of the amount of BiPbO₂NO₃ equilibrated with iodide ions. The unreacted iodide ions decreased very slightly with increasing BiPbO₂NO₃, indicating that the increment of total ion exchange capacity does not work effectively to decrease the iodide ions remained in the solution. The X-ray diffraction (XRD) pattern of BiPbO₂NO₃ did not change by the reaction. This does not mean that BiPbO₂NO₃ does not play a part in the ion exchange suggests that the peaks of the XRD patterns of the reaction products are too weak to be observed, because only a small area of the crystals reacts with iodide. Thermal properties were studied by TG-DTA/MS. A part of the reaction products decomposed at 315 degC - 455 degC and the decomposed compound contained CO₃. This can be explained so that the crystal surfaces of BiPbO₂NO₃ are covered with compounds such as Bi₂O₂(CO₃), disturbing the further process of ion exchange with iodide ions. Ion exchange reactions were examined by using two other simple solutions, one containing NaI and NaNO₃ and the other, NaI and Na₂CO₃. The effect of the coexisting anion on the ion exchange was examined as a function of its concentration