Determination of the thermal conductivity in zirconia based inert matrix nuclear fuel by oscillating differential scanning calorimetry and laser flash

The performances of oscillating differential scanning calorimetry (ODSC) and laser-flash technique in determining the thermal conductivity and the specific heat of zirconia-based materials, analogous to a potential nuclear fuel, were compared. The tested materials were (Zr1−x−y−z,Yx,Ery,Mez)O2−(x+y)/2, with Me=Ce or Th. The measured specific heats were around 0.4 J K−1 g−1 and the thermal conductivities ranged from 2 to 3 W K−1 m−1. The ODSC measurements resulted in cp values. The thermal conductivity was derived from two complementary measurements, one with a thin and the other with a thick sample. The laser-flash technique directly delivered the thermal diffusivity of the sample; consequently, the specific heat capacity cp has to be known for determining the thermal conductivity. The ODSC measurements were affected by the position of the sample on the support. This, consequently, influenced the reproducibility of the measurements. The reproducibility of the scans by laser flash was excellent. Thermal conductivity decreased with increase in the stabilizer (Y, Er) concentration. This trend was justified on the basis of a model including concentration and size of the oxygen vacancies.