Date of Award


Document Type

Campus Access Thesis


Nuclear Engineering

First Advisor

Travis W Knight

Second Advisor

Thad M Adams


Very high temperature reactors (VHTR) are capable of achieving temperatures up to 1000°C, allowing for increased plant efficiency, as well as the ability for using the process heat for hydrogen production and other commercial uses. However, the limits of operation of VHTRs are currently constrained by the ability of the tri-structural isotropic fuel (TRISO) to maintain its structural integrity under irradiation at temperatures of normal operation and accident scenarios. The silicon carbide (SiC) layer typical of most TRISO fuels acts as both a diffusion barrier and a pressure vessel for the fuel. This research focuses on the development of an advanced TRISO particle in which zirconium carbide (ZrC) layer is placed directly on the fuel kernel. The benefit of adding ZrC is that it is a good oxygen getter due to a low Gibb's free energy, forming a stable zirconium oxide and free carbon. This will help minimize typical TRISO fuel failures of the amoeba effect, cracking and over pressurization. The ZrC layer was initially deposited on surrogate zirconia kernels using a chemical vapor deposition (CVD) coater and the effects of varying gas flow rates were studied for optimization. The layers were analyzed by FESEM and confirmation was done through XPS and EDS. Also in this study, the reduction of U3O8 to UO2 took place through calcining and sintering at various heating parameters to minimize cracking. Once the coating parameters were sufficiently and reproducibility was confirmed, a ZrC layer was deposited on UO2 kernels.