Research Of Structure And Property Of Iron Sodium Phosphate Glass-ceramics Wasteforms

High-level radioactive waste?HLW?is mainly derived from the reprocessing process of spent fuel,and more than 99% of fission products in spent fuel are in high level radioactive waste.Therefore,the treatment of HLW is a matter of great concern to all countries.In this paper,20Fe₂O₃-60P₂O₅-20Na₂O was used as the base glass,ZrO₂ and CeO₂ as the oxide of simulated nuclear waste.The glass wasteform was prepared by melting cooling method,and the glass-ceramic wasteform was prepared by solid phase sintering method.The effects of ZrO₂ and CeO₂ on the structural properties,thermal properties and chemical stability of iron sodium phosphate glass and glass-ceramic wasteform were studied by XRD,FTIR and DSC.The main conclusions are as follows:?1?4 mol% ZrO₂ and 24 mol% CeO₂ can be immobilized in the iron sodium phosphate glasses,respectively.Glasses containing 4 mol%ZrO₂ have highest thermal stability and can enhance the strength of the glass network.When ZrO₂-Fe₂O₃-P₂O₅-Na₂O glasses were heat treated at 900 ?,the main crystal phase?Zr P2O7?was precipitation.With the increase of CeO₂,the thermal stability of the iron sodium phosphate glass increased firstly and then decreased.When theCeO₂-Fe₂O₃-P₂O₅-Na₂O glasses were heat treated at 650 750 ?,the main crystal phase?Na Fe P2O7?was precipitation.The predominant structural units of these two glass systems are Q1 units.?2?The main crystal phase,Na Ce2?PO4?3 and the minor crystal phase,Na Zr2?PO4?3 were precipitation from the iron sodium phosphate glass-ceramic wasteforms.and the most of Zr and Ce elements can be immobilized in the crystal phase.When the encapsulation capacity of nuclear waste was more than 55wt%,the content of crystalline phases decreased.The Q1 units are the predominant structural units,with the increase of nuclear waste content,the intensity of absorption peaks which was assigned to Q1 units weakened and bridging oxygen bond increased,which improved the chemical durability of wasteforms.The chemical stability of iron sodium phosphate glass-ceramic wasteforms was analyzed by MCC-1 static leaching experiment.When the wasteforms dipped in deionized water for 14 days,dissolution rate fell fast and then slow down and the dissolution rate of wasteforms was about 10-8 g/cm2·min.The concentration of Zr and Ce ions were lower than the limit of detection by ICP-MS and ICP-OES.Therefore,the iron sodium phosphate glass-ceramic wasteforms which immobilized ZrO₂ and CeO₂ has the strong chemical durable.