Radiocesium removal from high level liquid waste and immobilisation in sodium silicotitanate for geological disposal

The isolation of the fission product cesium from high-level alkaline liquid waste is studied with inorganic ion-exchange materials. High separation an d concentration factors can be obtained using sodium silicotitanate (CST). The leaching behaviour of cesium from CST was studied in clay porewater and Quinary brine at 90 degreesC. It is shown that cesium leaching in Quinary brine can be drastically reduced by thermal treatment of cesium loaded CST above 1000 degreesC. To this end, neutralisation of the ion exchange materi al before heating is required in order to reduce cesium volatility. It is c oncluded that CST is a good candidate material for geological disposal of t he fission product cesium.