Evaluation of Hydraulic Conductivities of Bentonite and Rock under Hyper Alkaline and Nitrate Conditions (III) (Summary)

Iriya, Keishiro*; Kubo, Hiroshi*

Circumstance of TRU waste repository shows alkaline condition due to leaching of cementitious materials. The waste containing significant soluble nitrate may changes ground water chemistry to high ion strength. Consolidation test and permeability test are carried out in order to assess quantitatively permeability of bentonite altered by hyper alkaline and nitrate. Modeling is progressed based on experimental results. The following results are obtained. 1)Consolidation test was carried out in 3 types of bentonite and 30% sand mixture in which kation exchanged with nitrate. It is noted that permeability of bentonite increased at from 40 to 200 times by kation exchange. 2)Permeability of hyper alkaline solution is almost same to water. Permeability of hyper alkaline solution with nitrates increased corresponding to rising ion strength.3)The results of batch of column test were simulated. The model can explain clearly the results in short period. This can estimate leaching ratio and secondary minerals. The model can simulate the experimental results by two types of velocity theory on altering bentonite.