3D Printing of Nuclear Fuel Assembly Bottom Nozzles

Metallic 3D printing of nuclear fuel assembly components has the potential to remove unwanted cost, waste, and time from the fabrication process. In addition to the direct manufacturing benefits, design engineers can create fuel assembly components that increase the performance of nuclear fuel assemblies with features that were not manufacturable a few years ago. Because of the reduced build time, each new design can be quickly iterated, producing rapid transitions between prototypes and final designs. For these reasons, the Department of Energy is highly interested in advancing methods of manufacturing for nuclear energy technologies that allow for easier engineering and commercial production of nuclear fuel assembly components. Overall, Phase I and II are focusing on optimizing the lower portion of the fuel assembly by adding beneficial 3D printed features and combining components. Phase I successfully built multiple bottom nozzle filter designs and fuel rod capture features. These were all tested for pressure drop, debris filtering efficiency, and fuel rod capture strength to vet which designs performed the best. Specifically addressing the bottom nozzle of a fuel assembly, 3D printing with Inconel-718 can enhance the debris filtering performance by constructing torturous flow passages that can be optimized for debris filtering efficiency and pressure drop. With the bottom nozzle being 3D printed, fuel rod capture features can be added to the bottom nozzle design, allowing for the removal of the lower end grid. Removing the lower end grid can lead to decreased fuel rod cladding wear by removing the contact point between the lower end grid to fuel rod and providing a more rigid fuel rod support. 3D printing a full-size bottom nozzle, analyzing specific features in different reactor environments, and performing full scale flow loop and irradiative testing are the main goals of Phase II. The commercial benefits for 3D printing in the nuclear industry are innumerable. A 3D printed bottom nozzle with fuel rod capture and debris filtering features can directly reduce cost by minimizing fuel rod failures, increasing the amount of fuel in a fuel rod, and decreasing the number of components. In general, the benefits to commercial nuclear reactor operators and the public are the countless areas where this technology can be applied to make nuclear components more efficient and thereby reducing the cost of electricity generated by nuclear power. Cost and time associated with material waste, quality control, inspection, and manufacturing of nuclear fuel assembly components can limit the efficiency of nuclear power plant operations. Using metallic 3D printing minimizes material waste and inspection time while producing close- tolerance products that increase quality and improve nuclear fuel assembly performance. 3D printing also frees designers to focus on component optimization, unhindered by standard manufacturing limitations.