UO2–Mo–Be composites for Accident Tolerant Fuel: SPS fabrication, microcracks-free in as-fabricated state and superior thermal conductivity

Abstract UO2–Mo composite pellets have been considered as an ATF (Accident Tolerant fuel) system for a nuclear reactor with high-safety-requirement. Nevertheless, since the mismatch of coefficient of thermal expansion (CTE) between UO2 and Mo, residual stresses will be produced in UO2–Mo composites during manufacturing. A novel type of UO2–Mo–Be composites pellets is fabricated to reduce the residual stresses caused by the mismatch of CTE. As a result, the problem of micro-cracks behavior caused by the CTE mismatch-induced stress in pellets with high Mo incorporation has been resolved. Compared with the pure UO2, the thermal conductivity of UO2–9Mo–6Be composites is increased by 128.65% at 298 K and 157.71% at 1273 K, respectively. The thermal conductivity of UO2–6Mo–4Be composites is also higher than that of UO2–10BeO composites and UO2–10Mo composites published in the literatures. While no irradiation test has been performed, such UO2–Mo–Be composites are expected to be an optimized candidate fuel system as an ATF.