The effect of processing on the thermal diffusivity of MgO–Nd2Zr2O7 composites for inert matrix materials

Oxides possess many of the required properties suitable for an inert matrix fuel in light water reactors, however, their primary disadvantage is low thermal conductivity. Composites are being investigated to maximize the thermal conductivity of the inert matrix fuel by using thermally conductive MgO as the primary phase while improving its hot water corrosion resistance through the addition of a second phase acting as a hydration barrier. Inert matrix fuel candidate MgO–Nd2Zr2O7 composites were synthesized with multiple processing methods, the composite powders were characterized, the resulting microstructures quantitatively analyzed, and the thermal diffusivity of the composites was measured. Among the four processing methods investigated, ball milling and high-energy shaker blending produced the most homogeneous microstructures with a negligible amount of MgO and Nd2Zr2O7 heterogeneities. An effect of processing on the properties of the composites manifests as a larger variation in the thermal diffusivity in pellets processed by methods that produce a higher quantity and frequency of MgO and Nd2Zr2O7 heterogeneities than in methods that produce negligible amounts of heterogeneities.