温度对含模拟α-高放核废液的磷酸镁水泥固化体性能的影响

Effects of Temperature on the Properties ofα-High-level Radioactive Waste Immobilized,Hardened Magnesium Phosphate Cement

利用磷酸镁水泥(Magnesium potassium phosphate cement,MPC)对模拟α-高放核废液(HLW)进行固化,研究温度对固化体力学性能、物相组成、微观形貌及核素Cs^+浸出率的影响。BET、XRD、SEM及AAS等测试结果表明,室温下MgO、KH2PO4与高放核废液反应形成致密结构;随着温度的升高,固化体脱水,400℃时孔道结构增多,平均孔径增大,抗压强度降低,Cs^+浸出率增加;温度继续升高,磷酸镁水泥烧结陶瓷化,平均孔径逐渐减小,抗压强度增大;900℃时固化体表现出良好的陶瓷结构特征,晶粒完全熔融,晶粒间没有明显界线,Cs^+的28d浸出率为7.21×10^(-6) g/(cm^2·d)。不同温度下高放核废液的磷酸镁水泥固化体核素Cs^+的浸出率均能达到玻璃固化体的性能要求,表明磷酸镁水泥用于固化高放核废液具有明显优势。

The magnesium potassium phosphate cement(MPC)were used for immobilization of liquid acidicα-high-level radioactive waste(HLW).This work focused on the impact of heat-treatment temperature on mechanical property,phase,microstructure and Cs+leaching rate of the solidified MPC.BET,XRD,SEM and AAS results showed that the ambient temperature reaction of MgO,KH 2PO 4 and HLW could form a dense structure,several kinds of phosphate was interspersed in the structure.The solidified MPC dehydrated with the increase of heat-treatment temperature,and obtained more pore structure,large average pore size,lower compressive strength and high Cs+leaching rate after sintering at 400℃.As the temperature continued to rise,the solidified MPC was sintered and formed ceramic while the average pore diameter decreased and the compressive strength increased.The solidified MPC turned into ceramic structure after sintering at 900℃.Crystal grains melt down completely.The 28 d leaching rate of Cs+in the solidified MPC was 7.21×10-6 g/(cm 2·d).The leaching rate of Cs+could reach the performance requirements of the vitrification form agent of the MPC solidified liquid with HLW at different heat-treatment temperatures,which showed obvious advantages of MPC in solidifying the HLW.