Thin Cold Sprayed Coatings for Nuclear Fuel with Enhanced Accident Tolerance

Following the nuclear accident at Fukushima Daiichi in 2011, the U.S. Department of Energy (DOE) launched a program to develop accident tolerant fuel (ATF). ATF is defined as nuclear fuel that can tolerate loss of active cooling in a reactor core for a considerably longer time period compared to the current standard systems. Cold sprayed chromium coatings applied to the outer diameter of zirconium-based nuclear fuel cladding tubes have been developed. The layer of chromium provides increased corrosion resistance under both normal operating conditions and in accident scenarios, with secondary benefits including wear resistance.

Significant development was necessary to deposit a very thin coating layer onto long and thin (on the order of 4m long and several mm in diameter) cladding tubes using the cold spray process, making this a first of a kind application both in the nuclear industry and in the cold spray industry. A final polishing process was utilized to reduce the as-deposited coating surface roughness and to adjust the thickness to the desired specifications. Using specific scale-up processes, pilot chromium cold spray coated fuel rods were inserted in a commercial nuclear reactor in early 2019.