New Method for the Solidification of High-Concentration Radioactive Borate Solution by Cement-Based Materials

• DOI: 10.3390/jcs6120392
• Publication Date: 2022-12-16T08:55:39Z
• Authors: Haosen Ma; Sensen Yuan; Haining Geng; Qiu Li
• Keywords: 02 engineering and technology; borate solution; Portland cement; hydration products; calcium metaborate; solidification; 0210 nano-technology; 12. Responsible consumption

Cement is widely used for the solidification of low- and intermediate-level radioactive waste materials. Radioactive borate solution with a high concentration of boron is one of the main radioactive wastes produced in nuclear stations. It is difficult to solidify this solution by using cement because borate has a great inhibitory effect on the cement hydration process. In this study, the hydration kinetics, strength, durability, phase assemblage, and transportation and transformation of the silicon of the paste that blended Portland cement with 5 M borate solution were investigated. After the addition of sodium hydroxide and sodium metasilicate to the paste, the cement hydration process was restarted, and the 28-days strength of samples met the requirements of the Chinese standard. The mechanism of overcoming the retardation of cement hydration by the borate solution was attributed to the formation of calcium metaborate, ettringite, portlandite, and calcium silicate hydrate with the restarting of cement hydration, without the formation of ulexite.