PWR cladding optimization for enhanced performance margins

As the nuclear power generating industry has matured there is an increasing trend in core operating fuel duties. This drives a continuing evolution of cladding materials, to provide performance margin and support even higher fuel duty designs. Westinghouse has developed an optimized version of ZIRLOTM, with a thin level reduced from the nominal standard ZIRLO level of 1% to a range of 0.6% to 0.8%. The lower tin level has been shown to reduce the clad corrosion of fuel rods during reactor core operation by 30% or more while still providing the mechanical and off-normal corrosion protection benefits associated with tin alloy additions. Peak oxide levels of only 20-30 μm are observed at burnups up to 63 MWd/kgU. Using relatively small changes in the final annealing temperature, the clad creep can be adjusted to meet target ranges. In-reactor measurements of creep and growth of Optimized ZIRLOTM verify mechanical characteristics equivalent to standard ZIRLO. (author)