PENGEMBANGAN TEKNOLOGI PENGOLAHAN LIMBAH RADIOAKTIF PRA-DISPOSAL : IMOBILISASI LIMBAH RADIOAKTIF URANIUM MENGGUNAKAN ABU BATUBARA SEBAGAI BAHAN MATRIKS SYNROC

TECHNOLOGY DEVELOPMENT OF INDUSTRIAL LIQUID RADIOACTIVE WASTE TREATMENT : THE IMMOBILIZATION OF URANIUM RADIOACTIVE WASTE USING COAL-ASH AS MATRIX MATERIAL OF SYNROC. The decommissioning of Phosphoric Acid Purification Facility – Petro Chemical of Gresik (PAPF-PCG) generates radioactive liquid waste containing uranium. The waste was treated by bio-oxidation process using bacteria for volume reduction of the waste to become radioactive sludge waste. The sludge waste must be immobilized by solidification process for preparation of disposal to ensure the safety of the environment in the present and future. This research aim to immobilization of the radioactive sludge waste by solidification using coal-ash as matrix material of titanate synroc. Immobilization process was carried-out by mix the radioactive sludge waste with coal-ash and precursor oxides namely BaO, CaO, and TiO2 as addition of matrix materials. The composition of matrix material of synroc using coal-ash and addition of precursor oxides (in weight %) i.e : Al2O3 (6.26); BaO (5.33); CaO (10.52); TiO2 (68.02) ; and SiO2 (6.07). Beside that the matrix material contains oxides minor (in weight %) i.e : Fe2O3 (3.48), MnO2 (0.04), K2O (0.20) and Na2O (0.08). Waste loading in the waste synroc block was 30 weight %. The mixture then was dried at temperature of 130 o C, and calcined at 750 o C. The powder of calcination result then was pressed in the molder. Furthermore, the sintering process was carried out at the temperature of 900 – 1300 o C for 1-4hours to form the solid multiphase ceramic of synroc block. The quality of the synroc block produced from immobilization was determined by testing of density, compressive strength, and leach-rateof uranium (the accelerated leach-rate at temperature of water 100 o C). The test results showed that the best quality of waste synroc block was obtained at the waste loading 30 % wt, sintering temperature of 1100 o C for 3.5 hours with values of density 2.29 g/cm 3 , compressive strength 6.97 kN/cm 2 , and leach-rate of uranium is 3.16x10 -6 g.cm -2 .day -1 . The quality of the waste synroc block produced by sintering process has fulfill the recommendation of IAEA.
Keywords: coal fly-ash, immobilization of waste, uranium waste, synroc.