Future nuclear power plants can provide a large-scale source of environmentally benign power generation while improving plant safety and minimizing proliferation risks. Some innovative reactor designs use uranium alloy fuel pins made with annular geometries that reduce fuel temperature and swelling compared to solid pins. To realize these benefits, high volume advanced manufacturing methods are needed to produce precise annular metallic fuel pins from uranium alloys such as U-Zr. Conventional fabrication methods for metal fuel—vacuum induction melting and injection casting—date back to the 1960s. These methods were originally developed to support fuel fabrication for the U.S. experimental fast reactors. Current injection casting production rates are too low for economical production. It is unlikely that injection casting is feasible for an annular pin, since the mold would need to be removed from the center of the pin after casting.
Novel Continuous Casting Process
Creare is developing a continuous casting process to produce annular metallic fuel pins. The process promises to meet precise dimensional requirements, minimize post-processing to keeps costs down, and reduce waste. It will produce pins with equiaxed, fine grains that are needed for good irradiation performance. Creare’s process uses innovative tooling, instrumentation, and control technology to economically produce annular fuel.
Our novel device pulls a casting directly from the surface of a pool of molten metal, using high intensity cooling to solidify the pin as it emerges from the pool.
In the next phase of development, advanced precision casting equipment will operate at very high temperatures (1300-1400°C) using a molten metal that more closely models nuclear fuel alloys. We will develop the equipment needed to produce the pins, run multiple series of fabrication experiments, and refine the design of the equipment based on the measured dimensions and metallurgical properties of the castings.
(Image above shows the cross-section of an annular casting. The 6 mm (approx.) outer diameter casting was made from a low melting temperature Bi-Sn alloy to demonstrate feasibility of producing annular fuel by continuous casting.)