Progress Toward Instrumented Nuclear Fuel Pellets Using Additive Manufacturing

Instrumented fuel pellets offer the potential to be used for the real-time measurement of fuel properties within emerging nuclear reactor designs. The use of three-dimensional (3D) printed nuclear fuel pellets is one approach to accommodate instrumentation. The 3D printing of nuclear materials requires that a printable feedstock material be developed for use with a specific additive manufacturing technology. In the present work, an iterative design process was used to formulate a filament containing yttria-stabilized zirconia, as a surrogate for uranium dioxide, that is suitable for use with fused filament fabrication 3D printers.

The components of the filament and their amounts, the printing parameters, and the debinding process were varied to produce an optimized printing procedure. A final five-component formulation containing 50.0 ± 0.1 vol % organic material was developed. With this formulation, the requirement to print to a 16-mm wall thickness, consistent with CANDU pellet dimensions rather than the maximum of 4 mm reported previously, resulted in numerous production failures. Ultimately, the manipulation of specific printer parameters to form microchannels within the pellet during printing resulted in pellets consistent with the target criteria. In the final set of eight pellets, seven pellets met the density criterion of 95% theoretical density, with an average density of 96.2 ± 1.0% of theoretical density.