Cementation of radioactive borate liquid waste produced in pressurized water reactors

The solidification of simulated radioactive borate liquid waste was investigated using sulfoaluminate cement (SAC) as main matrix material. The additives, including Ca(OH)2, zeolite, accelerator and polypropylene fiber were used to improve the performance of the solidified wastes. The experimental results indicated that the 28 days compressive strength of the solidified waste forms was 13.9 MPa, the leaching rate was 3.39 × 10−5, 4.45 × 10−5 and 4.07 × 10−7 cm/d for Sr2+, Cs+ and Co2+ respectively, meeting the requirement of the standard in GB 14569.1-1993. The SEM image and XRD pattern of solidified borate liquid waste forms revealed that the main hydrate of SAC improved the matrix strength and reduced the leachability. Boron, in form of B(OH)4−, incorporated in ettringite (3CaO·Al2O3·3CaSO4·32H2O) as solid solutions, and the basic structure of ettringite did not change. SAC is appropriate matrix for the solidification of radioactive borate liquid waste.