Contribution to the Zr-Rich Part of the Zn-Zr Phase Diagram

• Published in: Journal of phase equilibria and diffusion Vol. 25; no. 4; pp. 355 - 363
• Main Authors: Williams, Maureen E., Boettinger, William J., Kattner, Ursula R.
• Format: Journal Article
• Language: English
• Published: 01.08.2004
• ISSN: 1547-7037
• DOI: 10.1361/15477030420124

The reaction of zinc vapor with Zircaloy-4 and nuclear grade zirconium was investigated with various analytical techniques: optical metallography, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Based on the results, the Zr-rich part of the Zn-Zr phase diagram was revised. A eutectoid decomposition of (*b3Zr) occurs at 718 plus/minus 6 deg C with a composition of XZr = 0.865; this temperature is lower than the previously accepted 750 deg C eutectoid. The solubility of Zn in (*aZr) was determined to be at xz" = 0.0236, a maximum at 725 deg C. The intermetallic phase ZnZr2 was observed to occur in samples heat treated at 712 deg C and 725 deg C, but not in those heat treated at 700 deg C and 775 deg C. Spent nuclear fuel storage in the United States is a major concern for both the power utilities that operate nuclear power plants and the government regulating authority, the Nuclear Regulatory Commission (NRC). Due to delays in the completion of permanent storage facilities, increased long-term reliability for temporary storage systems is required.