Physical Property Evaluation Testing of Cement-Solidified Products Prepared from Simulated Liquid Waste

Kubo, Yoshikazu*; Sasaki, Tadashi*

In the low level radioactive waste treatment facility (LWTF), the cement solidification process is being studied on its applicability as a method for preparing waste packages from sodium-nitrate-containing low-level liquid waste generated at reprocessing plants. Solidification of nitrate solution waste: Solidification in a high temperature caused a rapid hydration reaction of cement, resulting in rapid hardening during the mixing process and a drop in fluidity. However, it has been confirmed that liquid waste can be solidified at 80C or so by adding a dispersing agent to improve fluidity and changing the amount of hardening solution to be added for cement hardening. This has verified that the cement solidification process under contemplation is applicable to nitrate-containing liquid waste. Solidification of slurry waste: In solidifying slurry waste, a fall in fluidity and a fall in compressive strength were observed. It is considered that this is attributed to the effects of phosphate contained in the liquid waste. In the case of slurry waste whose phosphate concentration is adjusted to 0g/L, it has been verified that solidified products whose salt mixing ratio is 50wt% can be prepared when the liquid waste temperature is 80C and the degree of concentration is 65wt%. It has been revealed that increases in the NaNO, NaHCO, and NaSO contents cause a delay in cement hardening, a fall in compressive strength, and a fall in fluidity, respectively. It has also been revealed that when liquid waste containing phosphate alone is solidified, solidified products whose salt mixing ratio is 50wt% in terms of hydrate salt (NaPO 8HO) (26.6wt% in terms of anhydrate salt) can be prepared.