Development of selective cobalt and cesium removal from the evaporator concentrates of the PWR Paks

Abstract

Summary At the PWR Paks (Hungary) the diluted radioactive waste water is converted to a concentrate by evaporation and the concentrate is stored in tanks. The most important radionuclides in these solutions are 134Cs, 137Cs and 60Co. In this research we studied granular potassium nickel hexacyanoferrate(II) as a Cs-selective ion-exchanger. Its capacity depended 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 increased with 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 be successfully used for the cobalt removal from evaporation concentrates. Experiments were performed both in the laboratory and at the PWR Paks.