Solidification of borate radioactive resins using sulfoaluminate cement blending with zeolite

The solidification of borate radioactive resins using sulfoaluminate cement (SAC) blending with zeolite was investigated, and the performance of SAC–zeolite matrix for immobilizing borate resin was evaluated based on the compressive strength, leachability and mineral phases of solidified waste forms. The experimental results showed that the 28 d compressive strength of resin SAC–zeolite waste forms was 18.8 MPa, the cemented waste forms meet the requirement of water, freezing, irradiation and impact resistance tests. The leaching processes of Cs+ and Co2+ were diffusion-limit step. The leachability of Cs+ was higher than Co2+ no matter what the matrix contained zeolite or not, but leachability of both cations was reduced by adding 5% zeolite. For SAC–zeolite matrix, the leaching rates of Cs+ and Co2+ were 6.40 × 10−5 cm/d and 1.62 × 10−7 cm/d, and the cumulative leaching fractions were 2.9 × 10−3 cm and 2.3 × 10−5 cm, respectively. The X-ray diffraction (XRD) analysis suggested that B(OH)4− was incorporated by substitution of SO4− in the crystalline structure of ettringite (3CaO·Al2O3·3CaSO4·32H2O).

► Borate radioactive resins could be solidified using SAC blending with zeolite.
► Adding 5% zeolite reduced the leachability of Cs+ and Co2+.
► XRD results showed that B(OH)4− was incorporated into ettringite.