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

Abstract

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.

Pronghorn Theory Manual

“…The dependence of thermal properties on the gas composition within the graphite voids is not considered. The same or slightly different values for ρ S , k S , and C p,S have been measured or used elsewhere [5,58,59,107,[176][177][178][179], with the except of large differences in specific heat [58,178] and thermal conductivity [180].…”

“…(12.8b) [178,179,181-183]. This discrepancy may be attributable to the assumption that the inner and outer layers have the same properties despite annealing of the inner layer during the silicon carbide deposition process[180,183].…”

Direct Synthesis of Vertical Self-Assembly Oriented Hexagonal Boron Nitride on Gallium Nitride and Ultrahigh Photoresponse Ultraviolet Photodetectors

“…Most of those methods have a specified dimension with a well-defined thickness, which is not suitable for thin film materials. Among the steady-state techniques, optothermal Raman (OTR) was introduced to measure the thermal conductivity of thin film materials, from ultra-thin graphene to the constituent layers in tristructural-isotropic (TRISO) particles, as a fast, nondestructive testing technique [17][18][19]. OTR is a swift and convenient technique combining the principle that the Raman mode is strongly temperature-dependent and the fact that the Raman laser can act as a heat source for local temperature rise [20].…”