Contact Author:
Dr. Erik Vance Mader
emader@epri.com
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F:208-524-1596
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Performance of Alloy M5™ Cladding and Structure

Garry Garner (AREVA-NP), Bruce Hilton (Idaho National Lab), Erik Mader (EPRI)
Achieving PWR fuel assembly burnups beyond currently licensed limits requires improved corrosion resistance as well as improvements in irradiation induced growth and creep. Over the last several years since the licensing of alloy M5™ for general use in the U.S., the performance of M5™ cladding and structural components in over 45 PWR’s world wide (including 12 in the U.S.) has been well documented in the literature. The subject of this paper is the performance of the alloy at burnups beyond currently licensed. In 1995, four fuel assemblies containing M5™ fuel rod cladding began a demonstration program in a 15x15 U.S. reactor that would result in several fuel rods achieving a peak rod burnup of greater than 70GWd/tU in four, 24-month operational cycles. In 1997, four advanced 17x17 lead assemblies with all M5™ fuel rod cladding and guide tubes were introduced into a higher duty U.S. PWR for 3 cycles with a fourth lead assembly achieving a peak rod burnup of greater than 70GWd/tU in four, 18-month operational cycles. Reactor poolside and hot cell post irradiation examinations (PIE) of fuel rods and guide tubes from these two high burnup demonstrations began in 2005 with some examinations continuing into 2006-07. The results of examinations performed to date confirm the excellent in-reactor behavior of alloy M5™ observed in European reactors with similar burnups but varying (lower and higher) duty indices.