An improved two-temperature method for computing the temperature distributions within a TRISO-coated particle pebble fuel

Abstract

With the world’s first pebble-bed modular high-temperature gas-cooled reactor beginning commercial operation in China, the tristructural-isotropic (TRISO) coated particle pebble fuel technology has garnered significant research interest and widespread attention. In light of the fact that temperature gradients within a pebble fuel may span several hundred degrees Celsius, it becomes imperative to attain a more precise and rapid determination of the internal temperature distribution. This work first developed an Improved Two-temperature Method (ITM) based on the analogous nature of heat and neutron diffusion processes, with deriving equations for three parameters $k_f$, $k_m$, and $\mu$, to achieve higher accuracy and wider application range. Then, seven tests were implemented for validating the ITM through comparing with finite element method, which can be considered identical with the analytic solution. Results show that the ITM can provide very accurate predictions of the peak temperature of both the fuel particles and the matrix. Finally, analysis of the influences of packing fraction and particle diameter on the temperature distribution within a pebble fuel, has been investigated, and it was found that there are two competing mechanisms resulting in the optimized design occurs at the packing fraction of 0.05, and the smallest particle diameter of 0.2 mm. The developed ITM and findings in this work provide tools and thermal conditions for analyzing fission gas release, creep rate, and other performance metrics of the pebble fuel.