Wet-chemical dissolution of TRISO-coated simulated high-temperature-reactor fuel particles

摘要

Chemical etching with different mixtures of acidic solutions has been investigated to disintegrate the twooutermost coatings from tri-structural isotropic coated particles containing zirconia kernels, which areused in simulated particles instead of uranium dioxide. A scanning electron microscope (SEM) was usedto study the morphology of the particles after the first etching step as well as at different stages of thesecond etching step. SEM examination shows that the outer carbon layer can be readily removed witha CrO3–HNO3/H2SO4 solution. This finding was verified by energy dispersive spectroscopy (EDS) analysis.Etching of the silicon carbide layer in a hydrofluoric–nitric solution yielded partial removal of the coatingand localized attack of the underlying coating layers. The SEM results provide evidence that the etching ofthe silicon carbide layer is strongly influenced by its microstructure.