The addition of silicon carbide to surrogate nuclear fuel kernels made by the internal gelation process

The US Department of Energy plans to use the internal gelation process to make tristructural isotropic (TRISO)-coated transuranic (TRU) fuel particles. The focus of this work is to develop TRU fuel kernels with high crush strengths, good ellipticity, and adequately dispersed silicon carbide (SiC). The submicron SiC particles in the TRU kernels are to serve as getters for excess oxygen and to potentially sequester palladium, rhodium, and ruthenium, which could damage the coatings during irradiation. Zirconium oxide microspheres stabilized with yttrium were used as surrogates because zirconium and TRU microspheres from the internal gelation process are amorphous and encounter similar processing problems. The hardness of SiC required modifications to the experimental system that was used to make uranium carbide kernels. Suitable processing conditions and equipment changes were identified so that the SiC could be homogeneously dispersed in gel spheres for subsequent calcination into strong spherical kernels.