Efficiency of Sulfoaluminate Cement for Solidification of Simulated Radioactive Borate Liquid Waste

Abstract

To investigate the solidification efficiency of sulfoaluminate cement (SAC) and to provide more information for formula optimization, SAC blending zeolite, accelerator and Dura fiber was used as matrix materials for solidification of simulated radioactive borate liquid waste. The simulated radioactive borate liquid waste was prepared with boric acid and sodium hydroxide using drinking water. The performances of solidified waste forms were evaluated mainly basing on matrix compressive strength and leachability. The 28d compressive strength of the solidified waste forms were tested according to Chinese National Standard GB 14569.1-1993, and experiments on water/freezing/irradiation/impact resistance were also carried out. Nuclides Sr, Cs and Co were substituted by their non-radioactive isotopes respectively in leachability test, and the testing procedures were consistent with Chinese National Standard GB 7023-1986. Experimental results showed that it was feasible to solidify borated liquid wastes with SAC. The 28d compressive strength was 13.9MPa, nearly twice of the standard in GB 14569.1-1993. Strength losses in water/freezing/irradiation/impact resistance tests met the demands of GB 14569.1-1993 well. In the leaching test, the 42d leaching rates were 3.39×10−5 cm/d, 4.45×10−5 cm/d and 4.07×10−7 cm/d for Sr2+, Cs+ and Co2+ respectively, much lower than GB 14569.1-1993 limits. Results of leaching test also showed that the leaching mechanism of Co2+ was different from that of Sr2+ and Cs+.