DEVELOPMENT FOR SELECTIVE CESIUM REMOVAL FROM THE EVAPORATION CONCENTRATES OF THE PWR PAKS

Abstract

At the Pressurized Water Reactor Paks the diluted radioactive wastewater is converted to concentrate by evaporation and the evaporator bottom is stored in tanks. The most important radionuclides in these solutions are 134Cs, 137Cs and 60Co. The volume reduction technologies like selective ion exchange for cesium and the ultrafiltration for cobalt may reduce the volume of the liquid waste and the burial costs. In our research we studied our granular potassium nickel hexacyanoferrate(II) as a Cs-selective ion-exchanger. Its capacity was depending on the preparation method, temperature of pretreatment and age of the ion exchanger. We investigated also the effect of metal ions (Fe2+, Fe3+, Mn2+, Mg2+, Ca2+, Co2+, Ni2+, Cu2+) on the Cs-capacity in the presence of complex forming compounds citrate, oxalate and EDTA. The cesium ion exchange capacity was increased in case of addition of inactive cobalt or nickel salts. Additionally, we studied filtration, adsorption and ultrafiltration separation processes for cobalt removal. The results showed that only adsorption by active carbon could successfully be used for the cobalt removal from the evaporation concentrates. Experiments were also performed in our laboratory and at the PWR Paks.