Optimization of the TRISO fuel particle distribution based on octahedral and icosahedral-based segmentation methods in the pebble-bed nuclear core

Abstract

The random distribution of TRISO fuel particles in the fuel elements may form local hotspots, thereby increasing the thermal stress on TRISO particle layers that may cause particle failures. Optimization of the distribution of TRISO fuel particles can significantly decrease the peak temperature, reducing the stress, and thus improve the safety and economy of the reactor. In this study, two optimization methods, namely octahedral and icosahedral-based segmentation optimization methods, were introduced to decrease the maximum temperature of the pebble fuel with packing fractions from 5% to 40%. ANSYS 19.1 was used to calculate the temperature distribution of pebble fuel elements with optimized and random TRISO particle distributions. The results showed that the optimization for the distribution of TRISO particles dispersed in the pebble fuel element is essential and feasible. The necessity and effectivity of optimization increase as packing fraction increases. The peak temperatures of the fuel pebbles with optimized TRISO particle distributions were significantly decreased in comparison with the ones with randomly distributed TRISO particle. The icosahedral-based optimization method is recommended among the two kinds of optimization methods because the effectivity of the icosahedral-based optimization method is higher than the octahedral-based ones and the icosahedral-based optimization method can also get a higher target packing fraction.