SPS Sintered Gd₂Zr₂O₇ Pyrochlore Waste Forms For Simulated TRPO Waste

Gd₂Zr₂O₇ pyrochlore is a well-cured substrate for the treatment of radionuclides such as Pu²³⁹,Np²³⁷,U²³⁸.At present,the preparation of Gd₂Zr₂O₇ pyrochlore waste use the high temperature solid phase method,but this method takes a long time.In this study,Gd₂Zr₂O₇ pyrochlore waste forms immobilized TRPO waste 1 and TRPO waste 2 were prepared by spark plasma sintering?SPS?.X-ray diffraction?XRD?,Raman spectroscopy?Raman?,electron backscattering?BSE?,scanning electron microscopy?SEM with EDS?and other test instruments were used to test the phase,structure and morphology of the samples.The XRD structure was refined by using Fullprof software to explore the unit cell parameters of the series samples.The density of the series of samples was tested by using the GH-120D densitometer,and the SRIM software was used to simulate the irradiation experiment.The research results are as follows:?1?According to the calculated experimental raw formula,Gd₂Zr₂O₇ pyrochlore waste forms immobilized TRPO waste 1 and TRPO waste 2 were sintered by SPS.The sintering temperature use 1600°C and 1650°C respectively.The sintering pressure use 30Mpa.Holding time is set to 3min.?2?Gd₂Zr₂O₇ pyrochlore waste forms immobilized TRPO waste 1:The series of samples have clear grain boundaries,uniform surface morphology and good compactness.With the increase of waste addition,the unit cell parameters of the sample increase and the unit cell volume expands.When the waste addition amount is0 wt.%,10 wt.%,the sample are single fluorite structure phase.When the waste addition amount is 20 wt.%⁵0 wt.%,the superlattice diffraction peak appeared.And other phases appear?Mo₂C,Mo?.When the amount of waste was 10 wt.%,no obvious element enrichment sign appeared on the surface of the sample.Under the SPS sintering condition,the maximum solid solubility of Gd₂Zr₂O₇ pyrochlore waste forms immobilized TRPO waste 1 is between 10 wt.%and 20 wt.%.?3?Gd₂Zr₂O₇ pyrochlore waste forms immobilized TRPO waste 2:The series of samples have clear grain boundaries,uniform surface morphology and good compactness.When the amount of waste increased from 0 wt.%to 60 wt.%,unit cell parameters and unit cell volume reduce.The series of samples show the single fluorite structure phase,the diffraction peak of the XRD pattern shifted to a large angle,and when the amount of waste was 20 wt.%⁶5 wt.%,the diffraction peak of Mo₂C began to appear,and the surface of sample appeared some balls.When the amount of waste added was 10 wt.%,no obvious element enrichment signs appeared on the surface of sample.Under the SPS sintering condition,the maximum solid solubility of Gd₂Zr₂O₇pyrochlore waste forms immobilized TRPO waste 2 is between 10 wt.%and 20 wt.%.?4?Gd₂Zr₂O₇ pyrochlore waste forms immobilized TRPO waste 1 series samples have an average density ranging from 6.043 to 6.664 g?cm^-3.In addition to the blank sample,when the amount of waste increased,the average density of sample is gradually reduced;Gd₂Zr₂O₇ pyrochlore waste forms immobilized TRPO waste 2series samples have an average density ranging from 6.043 to 6.873 g?cm^-3.In addition to the blank sample,when the amount of waste increased,and the average density of sample showed a decreasing trend.In general,the samples of Gd₂Zr₂O₇pyrochlore waste forms immobilized TRPO waste sintered by SPS have high density.