Preparation of the highly dense ceramic–metal fuel particle with fine-grained tungsten layer by chemical vapor deposition for the application in nuclear thermal propulsion

Abstract

The cermet fuel element was achieved by dispersing the UO₂ particles with or without tungsten (W) coating layer uniformly in the W matrix. It is considered to be a robust and secure fuel for use in nuclear thermal propulsion in the near future. In this study, the effect of deposition temperature on the densification and grain refinement of the W coating layer was investigated. A high-density (19.24 g·cm⁻³) W layer with a uniform thickness (~ 10 μm) and fine grains (~ 297 nm) was prepared by spouted-bed chemical vapor deposition. The prepared high-density, fine-grained W layer has the following advantages. It can prevent direct contact between fuel particles, resulting in a more uniform fuel distribution. In addition, it can decrease the reaction probability between the fuel kernel and H₂, and prevent the release of fission products from the fuel kernel by extending the diffusion path at grain boundaries more efficiently. Moreover, the high-density, fine-grained W layer showed outstanding thermal and mechanical performance. Its average hardness and Young’s modulus were approximately 7 and 200 GPa, respectively. The thermal conductivity of the W film was 101–124 W·m⁻¹·K⁻¹ at 298–773 K. This work furthers our understanding of the potential application of the high-density, fine-grained W layer in nuclear thermal propulsion.