The immobilization of radioactive sludge waste resulted from bio-oxidation process by using matrix material of SYNROC by sintering process

The decommissioning of Phosphoric Acid Purification - Petrokimia Gresik (PAP-PKG) facility 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 where contains uranium including long-lived alpha waste classification, it must be immobilized by solidification process. The objective of the research is to immobilize the radioactive sludge waste by solidification using matrix material of SYNROC. Immobilization process of the waste in SYNROC was carried-out by mix the radioactive sludge waste with precursor oxide, then drying the mixture, pressing in the moulder with and without addition of betonmix additive. Further process are by calcination and sintering at the temperature of 1000 - 1200 °C with the time 1-3,5 hours to form the solid multiphase ceramic. Immobilization process by SYNROC matrix using precursor oxide with composition (in % weight) i.e : Al₂O₃ (5,4); BaO (5,6); CaO (11,0); TiO₂ (71,4) and ZrO₂ (6,6). Waste loading in the SYNROC block are 20 - 60 % weight. The quality of the SYNROC block produced from immobilization was determinated by testings of density, pressing strength, and leaching-rate. The results showed that the optimum quality of SYNROC block was obtained at the waste loading 30 % weight without the betonmix additive, sintering process at 1200 °C for 3 hours with values of density 2,8 g/cm³, pressing strength 10,4 kN/cm², and leaching-rate 2,64 x 10^-4 g/cm².day. The quality of the SYNROC block producted by sintering process conform to the hot isostatic pressing process. (author)