| Abstract Scope |
Zirconium carbide (ZrC) is a candidate material for advanced coated particle fuels. In tristructural isotropic (TRISO) coated particle fuel concepts, ZrC could be used as a Silicon carbide (SiC) replacement for very-high temperature applications or extended service conditions where SiC would suffer decomposition or chemical attack from metallic fission products, such as Pd. Furthermore, ZrC coatings on kernels could be deployed to limit release of fission products from the kernel as shown in historic UO2* TRISO fuel forms. ZrC has been traditionally deposited using halogen-based precursors (e.g., ZrCl4), however, the formation of HCl during coating limits its use for direct coatings on uranium bearing kernels, requiring the use of intermediate or protective pyrolytic carbon (PyC) coatings due to chlorine penetration and resulting uranium dispersion. Considering fission product containment in the kernel, adding additional layers to the TRISO fuel architecture reflects increased complexity in the fuel specification, quality assurance and quality control. As such, it is desirable to explore halogen-free precursor options for ZrC deposition to allow direct deposition on kernel materials which would avoid a need for protective PyC coatings. To explore the viability of halogen free ZrC deposition, Fluidized bed chemical vapor deposition was used to coat batches of surrogate particles with single layers of ZrC using halogen and metal organic precursors with halogen-based precursor depositions serving as a baseline. These metal organic and halogen-based precursor coatings were then characterized through optical microscopy, SEM, EDS, EBSD, and XCT and compared to evaluate their viability. |