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

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 (σcs) 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.