Hydrogen pickup mechanism in zirconium alloys

Adrien Couet, Arthur Thompson Motta, Antoine Ambard, Robert J. Comstock

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

Because hydrogen ingress into zirconium cladding can cause embrittlement and limit cladding lifetime, hydrogen pickup during corrosion is a critical life-limiting degradation mechanism for nuclear fuel. However, mechanistic knowledge of the oxidation and hydrogen pickup mechanisms is still lacking. In an effort to develop such knowledge, we conducted a comprehensive study that included detailed experiments combined with oxidation modeling. We review this set of results conducted on zirconium alloys herein and articulate them into a unified corrosion theoretical framework. First, the hydrogen pickup fraction (Fh) was accurately measured for a specific set of alloys specially designed to determine the effects of alloying elements, microstructure, and corrosion kinetics on fH. We observed that fH was not constant and increased until the kinetic transition and decreased at the transition. fH depended on the alloy and was lower for niobium-containing alloys. These results led us to hypothesize that hydrogen pickup during corrosion results from the need to balance the charge during the corrosion reaction such that fH decreases when the rate of electron transport through the protective oxide increases. To assess this hypothesis, two experiments were performed: (1) micro-X-ray absorption near-edge spectroscopy (u, -XANES) to investigate the evolution of the oxidation state of alloying elements when incorporated in the growing oxide and (2) in situ electrochemical impedance spectroscopy (EIS) to measure oxide resistivity as a function of exposure time on different alloys. With the use of these results, we developed an analytical zirconium alloy corrosion model based on the coupling of oxygen vacancies and electron currents. Both modeling and EIS results show that as the oxide electric conductivity decreases the fH increases. These new results support the general hypothesis of charge balance. The model quantitatively and qualitatively predicts the differences observed in oxidation kinetics and hydrogen pickup fraction between different alloys.

Original languageEnglish (US)
Title of host publicationZirconium in the Nuclear Industry
Subtitle of host publication18th International Symposium
EditorsRobert J. Comstock, Arthur T. Motta
PublisherASTM International
Pages312-349
Number of pages38
ISBN (Electronic)9780803176416
DOIs
StatePublished - Jan 1 2018
Event18th International Symposium on Zirconium in the Nuclear Industry - Hilton Head, United States
Duration: May 15 2016May 19 2016

Publication series

NameASTM Special Technical Publication
VolumeSTP 1597
ISSN (Print)0066-0558

Other

Other18th International Symposium on Zirconium in the Nuclear Industry
CountryUnited States
CityHilton Head
Period5/15/165/19/16

Fingerprint

Zirconium alloys
Pickups
Hydrogen
Corrosion
Oxides
Oxidation
Alloying elements
Electrochemical impedance spectroscopy
Kinetics
Niobium
X ray absorption near edge structure spectroscopy
X ray absorption
Nuclear fuels
Embrittlement
Oxygen vacancies
Zirconium
Experiments
Degradation
Microstructure
Electrons

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

Cite this

Couet, A., Motta, A. T., Ambard, A., & Comstock, R. J. (2018). Hydrogen pickup mechanism in zirconium alloys. In R. J. Comstock, & A. T. Motta (Eds.), Zirconium in the Nuclear Industry: 18th International Symposium (pp. 312-349). (ASTM Special Technical Publication; Vol. STP 1597). ASTM International. https://doi.org/10.1520/STP159720160055
Couet, Adrien ; Motta, Arthur Thompson ; Ambard, Antoine ; Comstock, Robert J. / Hydrogen pickup mechanism in zirconium alloys. Zirconium in the Nuclear Industry: 18th International Symposium. editor / Robert J. Comstock ; Arthur T. Motta. ASTM International, 2018. pp. 312-349 (ASTM Special Technical Publication).
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Couet, A, Motta, AT, Ambard, A & Comstock, RJ 2018, Hydrogen pickup mechanism in zirconium alloys. in RJ Comstock & AT Motta (eds), Zirconium in the Nuclear Industry: 18th International Symposium. ASTM Special Technical Publication, vol. STP 1597, ASTM International, pp. 312-349, 18th International Symposium on Zirconium in the Nuclear Industry, Hilton Head, United States, 5/15/16. https://doi.org/10.1520/STP159720160055

Hydrogen pickup mechanism in zirconium alloys. / Couet, Adrien; Motta, Arthur Thompson; Ambard, Antoine; Comstock, Robert J.

Zirconium in the Nuclear Industry: 18th International Symposium. ed. / Robert J. Comstock; Arthur T. Motta. ASTM International, 2018. p. 312-349 (ASTM Special Technical Publication; Vol. STP 1597).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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N2 - Because hydrogen ingress into zirconium cladding can cause embrittlement and limit cladding lifetime, hydrogen pickup during corrosion is a critical life-limiting degradation mechanism for nuclear fuel. However, mechanistic knowledge of the oxidation and hydrogen pickup mechanisms is still lacking. In an effort to develop such knowledge, we conducted a comprehensive study that included detailed experiments combined with oxidation modeling. We review this set of results conducted on zirconium alloys herein and articulate them into a unified corrosion theoretical framework. First, the hydrogen pickup fraction (Fh) was accurately measured for a specific set of alloys specially designed to determine the effects of alloying elements, microstructure, and corrosion kinetics on fH. We observed that fH was not constant and increased until the kinetic transition and decreased at the transition. fH depended on the alloy and was lower for niobium-containing alloys. These results led us to hypothesize that hydrogen pickup during corrosion results from the need to balance the charge during the corrosion reaction such that fH decreases when the rate of electron transport through the protective oxide increases. To assess this hypothesis, two experiments were performed: (1) micro-X-ray absorption near-edge spectroscopy (u, -XANES) to investigate the evolution of the oxidation state of alloying elements when incorporated in the growing oxide and (2) in situ electrochemical impedance spectroscopy (EIS) to measure oxide resistivity as a function of exposure time on different alloys. With the use of these results, we developed an analytical zirconium alloy corrosion model based on the coupling of oxygen vacancies and electron currents. Both modeling and EIS results show that as the oxide electric conductivity decreases the fH increases. These new results support the general hypothesis of charge balance. The model quantitatively and qualitatively predicts the differences observed in oxidation kinetics and hydrogen pickup fraction between different alloys.

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Couet A, Motta AT, Ambard A, Comstock RJ. Hydrogen pickup mechanism in zirconium alloys. In Comstock RJ, Motta AT, editors, Zirconium in the Nuclear Industry: 18th International Symposium. ASTM International. 2018. p. 312-349. (ASTM Special Technical Publication). https://doi.org/10.1520/STP159720160055