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) an d laser-hash technique in determining the thermal conductivity and the spec ific heat of zirconia-based materials, analogous to a potential nuclear fue l, were compared. The tested materials were (Zr1-x-y-zYx,Er-y,Me-z)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 resultedin c(p) values. The thermal conductivity was derived f rom two complementary measurements, one with a thin and the other with a th ick sample. The laser-hash technique directly delivered the thermal diffusi vity of the sample; consequently, the specific heat capacity c(p) 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 wit h increase in the stabilizer (Y, Er) concentration. This trend was justifie d on the basis of a model including concentration and size of the oxygen va cancies. (C) 1998 Elsevier Science B.V. All rights reserved.