Leaching resistance study on immobilization of MnO2/HMSS with sorbed simulated nuclide strontium by metakaolin-based geopolymers

Abstract

Radioactive waste generated in nuclear energy utilization poses great environmental risks, and the safe disposal technology has become a hot research topic in the field of nuclear environmental security. Immobilization is a common radioactive waste disposal technique, and the leaching resistance of the solidified body is the key to safe disposal. In the study, metakaolin was used as a raw material to solidify strontium, a common nuclide in radioactive waste streams, and then conducted leaching resistance tests. Using control variables, the experiments were used to investigate the effects of adsorption pretreatment prior to solidifying, solidifying with and without the addition of adsorbent on the effect of immobilization. The leaching resistance of the solidified bodies were investigated in three leaching environments: 25℃ deionized water, pH=1 sulfuric acid solution, and 5%wt magnesium sulfate solution during the 42d test cycle. The results showed that both leaching rate and cumulative leaching fraction of the 42d samples for the leaching resistance of radioactive waste immobilization under the environment of deionized water at 25℃. For the three leaching conditions, the adsorption pretreatment with (4:1)MnO2/HMSS before solidifying or the addition of (4:1)MnO2/HMSS while solidifying could effectively improve the leaching resistance of solidified body, and the former was more effective. The results of this study can provide reference for the disposal of strontium-contanining radioactive waste.