UO2–Y2O3 ceramic nuclear fuel: SPS fabrication, physico-chemical investigation and neutron absorption evaluation

Highlights: • Promising UO₂-Y₂O₃ ceramic nuclear fuel pellets are fabricated via SPS technique. • Dynamics of UO₂-Y₂O₃ SPS consolidation is comparatively analyzed with that of UO₂-Gd₂O₃ and UO₂-Eu₂O₃. • (U,Y)O₂ solid solution formation by SPS is shown for the first time. • Stable pore formation is identified after addition 2 and 8 wt% of Y₂O₃. • The neutron absorption lab test is performed for SPS nuclear fuel samples with IFBAs. -- Abstract: The paper studies spark plasma sintering of UO₂-based ceramics nuclear fuel obtained from a mixture of pristine urania with 2 and 8 wt% of Y₂O₃ (integral fuel burnable absorber) produced by liquid-phase ultrasonic homogenizing. Densification dynamics of UO₂-Y₂O₃ system is investigated for the first time in the temperature range up to 1250 °C under spark plasma sintering (SPS) conditions followed by a comparative analysis with UO₂-Gd₂O₃ and UO₂-Eu₂O₃ analogs. Earlier unknown data on formation of (U,Y)O₂ solid solutions, isostructural to UO₂, under SPS conditions is presented. Structural changes manifested in stable pore and defect occurrence within the ceramics bulk are shown to depend on Y₂O₃ amount proving the occurrence of the Kirkendall effect, which is commonly known phenomenon in the field of traditional methods of fuel manufacturing. Microhardness (HV), compressive strength (σ_cs) and density (ρ) are found to degrade in the presence of Y₂O₃, however their values remain within acceptable limits. For the first time, neutron-activation analysis is implemented as a laboratory means to assess neutron absorption efficiency of the SPS fuels containing various IFBA additives (Gd₂O₃, Eu₂O₃, Y₂O₃). These novel results contribute to the fundamental knowledge on the range of possible applications available owing to nonconventional SPS technology, thus extending the methods palette of fuel fabrication as well as providing new characterization approaches to probe important fuel properties for nuclear power engineering field.