10:15 AM - 10:30 AM
[HCG31-06] Retardation of Cs and Sr leachings by geopolymer matrices with zeolte and titanate adsorbent
Keywords:Geopolymer, Disposal of radioactive waste, Potassium almino silicate hydrate, Calcium silicate hydrate
In this study, geopolymer samples from mixing of KOH, metakaoline and water glass were investigated in leaching experiments. From the leaching experiments of Cs and Sr from geopolymer with titanate, most of Sr was tightly remained after 90 days even without titanate. This means that K-A-S-H matrix formed after the mixing has high capacity for Sr storage. On the other hand, small part of Cs (around 4%) was leached out after 90 days. However, although it is well known that Cs and Sr are easily leached out from cement matrix (A. El-Kamash, et al., 2006, and M. Takaoka, et al., 2015), K-A-S-H matrix is better in terms of Cs and Ss storage. From sorption experiments of Cs and Sr by using powder C-S-H and K-A-S-H samples as matrix components of cement and geopolymer, it is cleared that K-A-S-H has higher sorption capacity than that of C-S-H. From desorption experiment of Cs and Sr using deionized water from the C-S-H and K-A-S-H, it is cleared that almost of Cs was desorbed from C-S-H even for one day, while 90% of Cs was remained in K-A-S-H under the same condition. Consequently, K-A-S-H matrix in geopolymer has higher retention capacity than that of C-S-H matrix in cement. We conducted safety assessment for geopolymer and cement waste form in pit type disposal system using leaching ratio obtained in this study. From results of the assessment, K-geopolymer would be applicable for safety encapsulation and disposal of Cs and Sr as waste form.