Method of solidifying lead iodide containing radioactive iodine

Purpose: To solidify PbI2 which is a sort of radioactive wastes produced from nuclear fuel re-processing plants into a stable state suitable to the final processing. Method: PbI2 to be processed is mixed with silicate and alkaline solution and subjected to hydrothermal reaction under the conditions at a temperature of 150 - 300 deg C and at a pressure of 100 - 500 kg/cm2 into solidification products. According to this method, since the operation temperature is relatively low (lower than 300 deg C), there is no worry for the thermal decomposition of PbI2. Further, since the hydrothermal reaction is adopted, dissolution and recrystallization of solidifying matrix (silica, calcium silicate, zeolite, feldspar, clay, etc.) and PbI2 proceed to change the bonding between each of the grains into crystalline bonding to provide firm and less soluble textures. (Ikeda, J.)