SYMPOSIA PAPER Published: 01 February 2018
STP159720160088

Post-Quench Ductility of Zirconium Alloy Cladding Materials

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The ductility of zirconium-based alloys after steam oxidation at high temperatures, followed by quenching in water, is of significant interest for the nuclear industry. High-temperature steam oxidation and quenching of nuclear fuel cladding occurs during postulated loss-of-coolant accidents. The industry is currently establishing in-reactor operation limits for peak cladding temperature and time at temperature based on the measured ductile-to-brittle transition of different cladding materials, both in the as-fabricated condition and using hydrogen charging as a surrogate for in-reactor operation.

Aiming to study possible differences in post-quench ductility caused by differences in chemical composition, extensive testing on Zircaloy-4, ZIRLO®, and Optimized ZIRLO™ cladding materials as a function of hydrogen content, extent of oxidation, and peak cladding temperature was performed. The results showed similar ductile-to-brittle transition for the alloys studied despite differences in chemical composition, with a decrease in the extent of oxidation to reach the ductile to brittle transition with increasing hydrogen content. Microstructural characterization was performed to investigate the evolution of the oxygen-enriched layer that forms underneath the oxide, both during the time at high temperatures and during cooling. Significantly different morphologies of the oxygen-enriched layer were observed with different cooling rates, particularly for alloys containing niobium. Possible mechanisms for the development of the oxygen-enriched layer are discussed.

Author Information

Mueller, Andrew, J.
Westinghouse Electric Company, Fuel Engineering and Safety Analysis, Pittsburgh, PA, US
Romero, Javier, E.
Westinghouse Electric Company, Fuel Engineering and Safety Analysis, Hopkins, SC
Partezana, Jonna, M.
Westinghouse Electric Company, Fuel Engineering and Safety Analysis, Pittsburgh, PA, US
Pan, Guirong
Westinghouse Electric Company, Fuel Engineering and Safety Analysis, Hopkins, SC
Mitchell, David, B.
Westinghouse Electric Company, Fuel Engineering and Safety Analysis, Hopkins, SC
Garde, Anand, M.
Westinghouse Electric Company, Fuel Engineering and Safety Analysis, Hopkins, SC
Atwood, Andrew, R.
Westinghouse Electric Company, Fuel Engineering and Safety Analysis, Hopkins, SC
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Details
Developed by Committee: B10
Pages: 1011–1038
DOI: 10.1520/STP159720160088
ISBN-EB: 978-0-8031-7642-3
ISBN-13: 978-0-8031-7641-6