Chemical diffusion coefficient of oxygen in thoria based fuel with 3 and 8 weight % urania

The chemical diffusion coefficients D˜ of oxygen in (Th1-yUy)O2+x cuboid specimens with 3 and 8 wt% UO2 were measured using the thermogravimetry method in the temperature range of 1316 K ≤ T ≤ 1428 K. The magnitude of the measured diffusion coefficients D˜ in these two specimens was as low as 5.3 × 10−11 ±2 × 10−11 m2 s−1 and as high as 4.5 × 10−10 ±2.2 × 10−12 m2 s−1 that generally increased with increasing uranium content. The activation energies for interstitial oxygen diffusion in the specimen thoria-urania matrix were found to range from 150.4 to 174.2 kJ mol−1, which was slightly higher than previously reported. An analytical solution approach with weight measurements was the technique used to assess the chemical diffusion coefficient in the specimens.