Structure Insides at the Reaction Interface Between Pyrochlore Glass-Ceramics and Stainless Steel Canister Under Hot Isostatic Pressing Conditions

As potential waste forms for immobilizing actinide-rich radioactive wastes, Eu₂Ti₂O₇ pyrochlore glass-ceramics were fabricated via hot isostatic pressing (HIPing) at 1200 ^oC. The structure at the reaction interface between the glass-ceramic waste form and the stainless steel (SS) canister under HIPing conditions were carefully investigated with SEM, TEM and synchrotron single crystal X-ray diffraction (SC-XRD). The interactions at the reaction interface led to the formations of a ∼10 µm thick Cr₂O₃ layer as the oxidation front of the SS and a layer of a mixed oxide phase (Eu_1.25SiCr_0.8Ti_1.2O_7.5) on the glass-ceramic side of the reaction interface. The crystal structure of such a unique mixed oxide phase was revealed indubitably with a combination of synchrotron SC-XRD and TEM assisted with a FIB-SEM system. The improved structural understanding of the reaction interface will help to support the utilization of HIPing as a versatile hot consolidation process for the treatment of radioactive wastes.