Cobalt and cesium sorption characteristics in mixture of bentonite and fly ash for use in backfill material

Fly ash and bentonite samples were selected and their characteristics were investigated. Fly ash was found to be similar to bentonite in particle size distribution but quite different in microstructure. The most special aspect of fly ash was high alkalinity of its solution. Distribution coefficients of Cesium(Cs) and Cobalt(Co) in the samples were measured to survey the effects of mixing. Fly ash showed a higher distribution coefficient for Co than for Cs. Through various experiments, factors affecting the distribution coefficients of Co and Cs on mixtures of bentonite and fly ash were identified. Comparison of the distribution coefficients of Cs on fly ash and bentonite mixtures with those on sand and bentonite mixtures suggests that fly ash would be useful as an effective additive of backfill material if the proper mixing ratio was chosen. (author)