EVALUATION OF ZIRCONIUM 1.5 W/O NIOBIUM CLADDING FOR USE IN BOILING WATER REACTOR ENVIRONMENTS

Technical Report · Mon Oct 01 04:00:00 EDT 1962

OSTI ID:4747082

Rous, W C; Baroch, C J

Research has indicated that a Zr --1.5 wt% Nb alloy has a corrosion rate in 680 deg F water and 750 and 900 deg F steam about the same as Zircaloy-2, and a hydrogen pickup rate about 1/4 that of Zircaloy-2. It was also reported that the hydride in the Zr--Nb alloy apparently precipitated as spherically shaped particles rather than thin plates. Based on the favorable results of these corrosion tests an AEC Fuel Cycle Special Assembly 6L was designed to test the irradiation performance of Zr --1.5 wt% Nb as fuel rod cladding. Sixty-six feet of Zr --1.5 wt% Nb tubing was obtained to fabricate assembly 6L. Concurrent with the fabrication of the 6L assembly, samples of the tubing were corrosion tested with a surface heat flux of 205,000 BTU/ hr-ft/sup 2/. Under these conditions, the corrosion rate of the Zr--Nb tubing was found to be 6 to 10 times that of Zircaloy-2. The as-received Zr--1.5 wt% Nb tubing was annealed at a temperature which favored the formation of an alpha plus beta structure. It was demonstrated that the alpha stabilized structure is far more corrosion resistant than the alpha plus beta structure. Therefore, a sample of the tubing was annealed to stabilize the alpha structure and the BWR corrosion test repeated. The corrosion rate of the alpha stabilized Zr --1.5 wt% Nb tubing was still 6 to 10 times that of Zircaloy-2. Consequently, the Zr--1.5 wt% Nb tubing was replaced by Zircaloy- 4 as the clad material for the 6L assembly. Research conducted since June 1961 has indicated that the corrosion resistance of the Zr--Nb alloys is quite sensitive to the nitrogen content in a BWR environment, but in 750 deg F and higher temperature steam, the corrosion rate is relatively insensitive to the nitrogen content of the alloy. The poor corrosion resistance of the Zr-1.5 wt% Nb tubing was probably caused by high nitrogen content, 170 ppm, which had not affected the alloy performance in steam corrosion tests. (auth)

• Research Organization: General Electric Co. Atomic Power Equipment Dept., San Jose, Calif.
• NSA Number: NSA-17-016586
• OSTI ID: 4747082
• Report Number(s): GEAP-4098
• Country of Publication: United States
• Language: English

Related Subjects

ABSORPTION
ALLOTROPY
ANNEALING
CORROSION
CORROSION PROTECTION
FUEL CANS
HIGH TEMPERATURE
HYDRIDES
HYDROGEN
IRRADIATION
METALS, CERAMICS, AND OTHER MATERIALS
NIOBIUM ALLOYS
NITROGEN
PLATES
PRECIPITATION
QUANTITY RATIO
REACTION KINETICS
REACTORS
RODS
SENSITIVITY
SPHERES
STEAM
TUBES
WATER
ZIRCALOY
ZIRCONIUM
ZIRCONIUM ALLOYS
ZIRCONIUM-ALPHA
ZIRCONIUM-BETA