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

• Published in: Journal of nuclear materials Vol. 420; no. 1; pp. 342 - 346
• Main Authors: Skolo, K.P., Jacobs, P., Venter, J.H., Klopper, W., Crouse, P.L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 2012; Elsevier
• Subjects: Applied sciences; Carbon; Coatings; Controled nuclear fusion plants; Dissolution; Energy; Energy. Thermal use of fuels; Etching; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Nuclear fuels; Preparation and processing of nuclear fuels; Scanning electron microscopy; Silicon carbide; Simulation; Zirconium dioxide; Electron microscope; High temperature reactor; Silicon carbide; Zirconium oxide; Uranium; Coated particle; Nuclear fuel; Microstructure; Carbon; Dissolution; Protective coatings; Nuclear reactor
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2011.09.016

► TRISO coated particles were etched with different acidic solutions. ► The outer pyrolytic carbon layer was readily removed with CrO 3 -HNO 3/H 2SO 4 at 130 to 140 °C. ► Partial removal of the silicon carbide layer was observed. ► Scanning electron microscopy revealed localized attack of the underlying layers. Chemical etching with different mixtures of acidic solutions has been investigated to disintegrate the two outermost coatings from tri-structural isotropic coated particles containing zirconia kernels, which are used in simulated particles instead of uranium dioxide. A scanning electron microscope (SEM) was used to study the morphology of the particles after the first etching step as well as at different stages of the second etching step. SEM examination shows that the outer carbon layer can be readily removed with a CrO 3–HNO 3/H 2SO 4 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 coating and localized attack of the underlying coating layers. The SEM results provide evidence that the etching of the silicon carbide layer is strongly influenced by its microstructure.