TiO sub(2) doped UO sub(2) fuels sintered by spark plasma sintering

UO sub(2) fuels doped with oxide additives Cr sub(2)O sub(3) and TiO sub(2) display larger grain size, improving fission product retention capability and thus accident tolerance. Spark plasma sintering (SPS) was applied to consolidate TiO sub(2)-doped UO sub(2) fuel pellets with 0.5 wt % dopant concentration, above its solubility, in order to induce eutectic phase formation and promote sintering kinetics. The grain size can reach 80 mu m by sintering at 1700 degree C for 20 min, and liquid U-Ti-O eutectic phase occurs at the triple junction of grain boundaries and significantly improves grain growth during sintering. The oxide additive also impedes the reduction of the initial hyperstoichiometric fuel powders to more stoichiometric fuel pellets upon SPS process. Thermal-mechanical properties of the sintered doped fuel pellets including thermal conductivity and hardness are measured and compared with undoped fuel pellets. The enlarged grain size (80 mu m) and densification within short sintering duration highlight the immense possibility of SPS in fabricating large grained UO sub(2) fuel pellets to improve fuel performance.