Isothermal oxidation of zirconium using steam

Conference · Wed Jul 01 04:00:00 EDT 2020

OSTI ID:23030265

Vazquez Chavez, Julio Giuseppe ^[1]; Hanson, Bruce; Cochrane, Robert; Fernandez-Garcia, Javier ^[1]

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1. School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT (United Kingdom)

Oxidation of zirconium and its alloys under any atmosphere is generally characterised by a protective and non-protective stage. During the protective stage, the kinetics of oxidation are quasi-parabolic, while the oxide scale formed on the surface of the metal is black, compact, and protective in nature. For the non-protective stage, the oxidation rate becomes linear, while the protective oxide film turns into a deteriorated white scale. Breakaway is known as the transition point from protective to non-protective stage. The actual mechanism leading to breakaway of zirconium is still a matter of controversy, however some of the most common factors affecting breakaway are the following: - Impurities on the metal (Carbon, Oxygen, Nitrogen); - Oxidizing atmosphere (Presence of H{sub 2}O (g) or N{sub 2} (g)); - Sample preparation (Chemically etched or polished); - Temperature (LWR, LOCA). This research investigates the effect of temperature on 'breakaway' when zirconium is oxidized isothermally in steam for 60 min at 800 and 900 deg. C using thermogravimetric and optical microscopic imaging techniques. 1. Steam isothermal oxidations were performed on zirconium at 800 and 900 deg. C using a Thermogravimetric Analyzer (TGA). 2. Log-log plots of mass gain vs time were obtained from thermogravimetric results to calculate the reaction orders (n) and reaction rate constants (K) during oxidation. 3. Results of the kinetics of reaction were correlated with optical microscopic images form Light Microscope (LM) and Scanning Electron Microscope (SEM). Breakaway depends very strongly on temperature. At 800 deg. C, the weight gain followed a cubic-parabolic behaviour with evidence of a protective oxide film. On the other hand, oxidation at 900 deg. C showed signs of breakaway since the oxide film was cracked and oxidation rate was almost linear throughout the reaction.

• Research Organization: WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
• OSTI ID: 23030265
• Report Number(s): INIS-US--21-WM-20-P20576
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
ALLOYS
CARBON
LOSS OF COOLANT
MICROSCOPES
NITROGEN
OXIDATION
OXIDES
OXYGEN
REACTION KINETICS
SAMPLE PREPARATION
SCANNING ELECTRON MICROSCOPY
STEAM
THERMAL GRAVIMETRIC ANALYSIS
ZIRCONIUM