Study on damage degradation and radon emission from uranium tailing polymer-solidified soil under freeze-thaw cycles

Uranium tailing ponds are a long-term potential source of radioactive pollution. Solidification treatment of uranium tailings in ponds can effectively control the diffusion and migration of radioactive materials. This study examined uranium tailings, from the beach of a uranium tailing reservoir in China, as the research object. Sodium hydroxide and water glass were used as alkali stimulants and mixed with metakaolin and fly ash to prepare five types of solids with different proportions. The freezing and thawing (FT) temperatures were set at −20 to 20℃, and 25 FT cycles were performed. The microstructure, mass loss, compressive strength, cumulative radon concentration, and radon extraction rate of the samples before and after FT were determined. The results showed that the FT cycle had a significant impact on sample surface structure. The incorporation of fly ash effectively reduced sample mass loss and inhibited radon emission. As the number of FT cycles increased, sample mass loss gradually increased, compressive strength gradually decreased, and radon emission rate gradually increased. There was an inverse correlation between the mass change of a solidified sample and the rate of radon emission. Compressive strength and radon emission rate were also negatively correlated. Considering the three indicators of mass loss, compressive strength, and radon extraction rate with metakaolin as the solidified base material, the conclusion was that 55%MK+45%F was the optimal ratio for this purpose. (author)