Evaluation of thermal conductivity of the constituent layers in TRISO particles using Raman spectroscopy

The thermal conductivity of individual layer in the tristructural-isotropic fuel particle was evaluated using Raman spectroscopy. In this method, laser acted simultaneously as an excitation source and a heating source. A three-dimensional point-heating model was developed to estimate the local temperature rise in the probing volume of the laser. The thermal conductivity can be evaluated based on the dependences of the Raman peak position on the temperature and laser power. The calculated thermal conductivities were 8.9 ± 0.2 W/m °C, 13.9 ± 1.5 W/m °C and 11.9 ± 0.9 W/m °C for the buffer, the inner and the outer PyC layers, respectively. Contrastly, the thermal conductivity of the SiC layer was 4.1 W/m °C, which is much lower than the reference value, e.g. 168 W/m °C reported by López-Honorato et al. (J. Nucl. Mater. 378(1) 35-39, 2008). The uncertainty of employing Raman spectroscopy to determine thermal conducitvity was discussed.