Radwaste oil immobilization in geopolymer after non-destructive treatment

Abstract Lubricating oils in nuclear power plants may be contaminated with radionuclides and become a challenging radwaste for treatment as they decompose in storage and disposal and do not lend themselves to conventional cementitious stabilization methods. This work addresses the radwaste immobilization using geopolymer (alkali-activated material), an innovative technology relevant due to its advantages, compared to cement and bitumen. Two non-destructive processes for oil treatment were previously employed: the first was bentonite used as a sorbent material for oil decontamination and the second, a commercial polymer with total absorption of the oil. For both alternatives, the treated waste was immobilized in a geopolymer matrix and the final properties of the waste sample were assessed, such as compressive strength, leaching characteristics and homogeneity. The results were analysed according to the Brazilian legislation as a reference. The compressive strength was measured after 28 days and the results for impregnated bentonite immobilized in the geopolymer was found to comply with the regulation, but improvements must be made in the case of the oil in the commercial polymer. The leaching mechanism was diffusion controlled and the leaching rate of 150 days comply with the Brazilian regulation for both types of immobilized waste. SEM micrograph images confirm the homogeneity of the waste. To the extent of the author's knowledge, this is the first publication addressing the waste performance and its main properties for final disposal. The immobilization in a geopolymer is a promising technology as far as this type of waste is concerned.