METHOD FOR IMMOBILIZING CESIUM RADIONUCLIDES IN CERAMICS Russian patent published in 2024 - IPC C04B35/19 G21F9/16 

FIELD: chemical or physical processes.

SUBSTANCE: invention relates to methods of immobilizing radionuclides in aluminosilicate ceramics and can be used in burial of radioactive wastes of various activity and in radiochemical industry when producing finished products with given specific activity. Method for immobilizing cesium radionuclides in ceramics comprises preparing zeolite powder, saturation with a calculated amount of cesium radionuclides by immersion in a cesium chloride solution followed by holding for 24 hours at room temperature. Powder of zeolite, adsorption saturated with cesium, is pre-compacted in graphite mold, workpiece is subjected to spark plasma sintering in vacuum at constant pressing pressure and sintering temperature 900–1,000 °C, wherein the sintering temperature increase is controlled in steps: in the range of up to 650 °C, the heating rate is 300 °C/min, and from 650 °C and higher—90 °C/min. At the stage of zeolite preparation one mixes distilled water, 2.06 M aqueous solution of Na₂SiO₃ and 0.28 M aqueous solution of NaAlO₂, the obtained hydrogel with molar ratio Na₂O·Al₂O₃ : SiO₂ : H₂O, equal to 3.4:2:170, stirred at speed of 1,200 rpm at temperature of 25 °C for 30 minutes and subjected to crystallisation by hydrothermal method at temperature of 90–150 °C with pitch of 10 °C and holding for 24 hours at achieved temperature of each step. Precipitated zeolite is separated, washed and dried in air at temperature of 90 °C for 4 hours.

EFFECT: reliable immobilisation of cesium in the composition of ceramics, where the amount of immobilized cesium is 24.3 wt.%, cesium leaching rate is not more than 10⁻⁶–10⁻⁷ g/cm²·day, thermal stability in air is up to 1,000 °C.

1 cl, 10 dwg, 2 tbl