부산대학교 도서관

There are high yields of 90Sr radionuclide present in the spent fuels from nuclear power plants. Permanent disposal of the nuclear waste requires immobilization of the highly radioactive materials. We investigate strontium titanate as a model waste form for 90Sr. Coimplantation with O+and Zr+ions, followed by annealing at 1423 K, was performed to simulate 90Sr to 90Zr decay. The microstructures were examined using a state-of-the-art aberration-corrected scanning transmission electron microscope (STEM) with a spatial resolution of better than 0.1 nm. At low Zr concentrations, we observe formation of a ZrO-Sr superlattice structure. Ab initio calculations indicate that this atomic configuration is energetically favorable. At higher Zr concentrations, we observe precipitates of ZrO2with a coherently strained interface or a monolayer of disordered interfacial structure. Chemical and charge effects in the model waste form of 90SrTiO3are discussed.