Microwave-assisted low temperature synthesis of sodium zirconium phosphate (NZP) and the leachability of some selected fission products incorporated in its structure — A case study of leachability of cesium

摘要

Microwave-assisted procedure for low temperature solid state synthesis of sodium zirconium phosphate (NZP), a material with the potential for immobilization and disposal of high level nuclear waste, was developed. Three selected fission products, namely, Cesium, Strontium and Tellurium were introduced (substituted) in the NZP matrix during its synthesis at 450°C. Leaching studies were carried out on the fission product substituted NZP sintered at 1000°C, in pure de-ionized water and 80% saturated brine solution at the ambient temperatures of 30°C and 90°C for four weeks. The major part of leaching in all the cases was observed in the first week. The extent of leaching after four weeks was found not exceeded from 12 to 15% of the elements substituted in NZP, which later became negligibly small. The effect of temperature and the nature of leachant on the leaching rate did not indicate any systematic trend. The EDX analysis of the surfaces of the leached NZP pellets showed that the leaching of the dopants is limited mainly to the surface region of the sintered pellets. Keywords Microwave aided synthesis - SEM - EDX - XRD - HLW immobilization - leaching