SYMPOSIA PAPER Published: 01 January 1989

Development of a Cladding Alloy for High Burnup


An advanced Zircaloy cladding containing niobium has been developed and tested extensively both in long-term out-of-pile autoclave exposures and through high burnup irradiation in a pressurized water reactor (PWR) environment. Tubing of zirconium-based binary alloys containing 0.5, 1.0, and 2.5% niobium, and a quaternary composition containing tin, niobium, and iron was fabricated in such a manner that the second phase was fully precipitated, but with minimal particle growth. Autoclave testing in pure water and steam over the temperature range of 589 to 727 K indicates that all of the alloys except the 0.5% Nb have a lower post-transition corrosion rate than does Zircaloy-4, with the relative benefit increasing with temperature. Additional autoclave testing in LiOH solutions indicated a marked sensitivity of the Nb binaries to accelerated corrosion, and in these solutions only the Sn-Nb-Fe alloy was superior to Zircaloy-4. Experimental fuel assemblies with cladding of the advanced alloys were examined after one, three, and four cycles in the BR-3 reactor. Rod average burnups of up to 71 GWD/MTU were obtained with total residence times of up to 66 months. Results of post-irradiation examinations are given only for the Sn-Nb-Fe alloy as compared to Zircaloy-4. These examinations revealed that the Sn-Nb-Fe alloy showed the lowest overall corrosion, up to 50% better than Zircaloy-4 at the highest burnups, and was superior to the Zr-Nb binaries. The Sn-Nb-Fe alloy, called ZIRLO, also displayed lower irradiation growth and creep than the others.

Author Information

Sabol, GP
Westinghouse Electric Corporation, Research and Development Center, Pittsburgh, PA
Kilp, GR
Westinghouse Electric Corporation, CNFD, Monroeville, PA
Balfour, MG
Westinghouse Electric Corporation, CNFD, Monroeville, PA
Roberts, E
Materials and Mechanical Process Development, Westinghouse Electric Corporation, CNFD, Columbia, SC
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Developed by Committee: B10
Pages: 227–244
DOI: 10.1520/STP18868S
ISBN-EB: 978-0-8031-5084-3
ISBN-13: 978-0-8031-1199-8