Preliminary study of cesium immobilization in a geopolymer matrix

Geopolymers are modern synthetic materials that have many beneficial characteristics, e.g. excellent mechanical properties, fire-and heat-resistance, minimal shrinkage and can be molded into shape. Given their aforementioned characteristics, geopolymers could be applicable as conditioning materials, e.g. to handle hazardous waste and radioactive materials. However, their long-term applicability needs to be investigated. The aim of this study is to investigate the mobility of Cs-137 radionuclides in embedding materials. Different geopolymeric matrices -namely kaolinite, bentonite, zeolites and red mud -were tested. The leach test was performed according to the ASTM C1308-08(2017) standard and the activity concentration of Cs-137 isotopes was measured by gamma spectrometry using a high-purity germanium (HPGe) semiconductor detector. According to our preliminary results, the matrices that resulted in the most significant immobilization effect were those in which bentonite, cement, fly ash and 8M NaOH were used, releasing approximately 10% of the cesium.