Effect of microstructure on the resilience of silicon carbide to palladium attack

The Pd/silicon carbide (SiC) reaction rate in tristructural isotropic (TRISO)-coated fuel particles has been studied. We have shown that it is possible to reduce the attack by palladium significantly by controlling the SiC microstructure. Large grain sizes as well as high coating rates did not increase the attack by Pd as previously thought. The activation energy for the Pd/SiC reaction obtained for the optimized SiC coatings, 337 kJ/mol, is almost twice as high as for standard coatings (∼160-190 kJ/mol) and five times higher than for porous samples (67 kJ/mol). An increase of the (111) texture component and the characteristics of the grain boundaries are suggested as possible reasons for reduction of the Pd/SiC reaction.