고준위 방사성폐기물의 고정화를 위한 Fe-석류석 합성 연구 = Synthesis of Fe-Garnet for the Immobilization of High Level Radioactive Waste

다국어 초록 (Multilingual Abstract)

Garnet has been considered as a possible matrix for the immobilization of radioactive actinides. It is expected that Fe-based garnet be able to have the high substitution ability of actinide elements because ionic radius of Fe in tetrahedral site is larger than that of Si of Si-based garnet. Accordingly, we synthesized Fe-garnet with the batch composition of Ca_(2.5)Ce_(0.5)Ze₂Fe₃O_(12) and Ca₂CeZrFeFe₃O_(12) and studied their phase relations and properties. Mixed samples were fabricated in pellet forms under the pressure of 400 ㎏/㎠ and were sintered in the temperature range of 1100- 1400℃ in atmospheric conditions. Phase identification and chemical composition of synthesized samples were analyzed by XRD and SEMIEDS. In results, where the compounds were sintered at 1300℃, we optimally obtained Fe-garnets as the main phase, even though some minor phases like perovskite were included. The compositions of Fe-garnets synthesized from the batch compositions of Ca_(2.5)Ce_(0.5) Zr₂Fe₃O_(12) and Ca₂CeZrFeFe₃O_(12), are Ca_(2.5-3.2)Ce_(0.3-0.7)Zr_(1.8-2.8)Fe_(1.9-3.2)O_(12) and Ca_(2.2-2.5)Ce_(0.8-1.0)Zr_(1.3-21.6)Fe_(0.4-0.7)Fe_(3-3.2)O_(12) respectively. Ca contents were exceeded and Ce contents were exceeded or depleted in 8-coodinated site, comparing to the initial batch composition. These results were caused by the compensation of the difference of ionic radius between Ca and Ce.