Fuel performance improvement program. The development of graphite-coated cladding for improved PCI performance of LWR fuels

One of the fuel concepts being tested and demonstrated as part of the Fuel Performance Improvement Program includes a graphite coating applied to the inner surface of the Zircaloy cladding. The technology for producing acceptable coatings was developed starting with the selection of a suitable graphite and culminating with the coating of 200 cladding tubes for demonstration irradiations in the Big Rock Point Reactor. During the process development, methods for controlling the coating thickness and minimizing its hydrogen content were developed that were compatible with production scale operation. During the same period, the graphite coatings were characterized and their properties were determined, mainly to provide information needed for fuel design and licensing considerations. Purity, structure, coating-to-cladding compatibility, thermal conductivity, and friction/wear characteristics were measured