Positron annihilation analysis of the atomic scale changes in oxidized Zircaloy-4 samples

J. Heikinheimo, S. Ortner, I. Makkonen, J. Kujala, M. Blackmur, F. Tuomisto

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)

Abstract

The process of oxidation in zirconium alloys is not straightforward. It includes cyclic periods, where the oxidation rate is decelerating as a function of increasing oxide thickness. Transition to the higher oxidation rate happens approximately after every 2 μm oxide growth and each cycle is associated with a layer of oxide with little or no cracking and a similar thickness layer with a large number of micro-scale lateral cracks. This work uses positron annihilation Doppler broadening spectroscopy to investigate the development of atomic-scale defect features in the oxides on Zircaloy-4 samples exposed to alkaline water at 350 °C. Results from the Doppler broadening measurements supported by Density Functional Theory calculations indicate that complexes involving both zirconium-site and oxygen-site vacancies exist in the oxide. The implications of the vacancies in the oxide layer are considered for oxygen diffusion and the oxidation rate.

Original languageEnglish
Pages (from-to)172-180
Number of pages9
JournalJournal of Nuclear Materials
Volume495
DOIs
Publication statusPublished - Nov 2017
MoE publication typeNot Eligible

Fingerprint

Positron annihilation
positron annihilation
Oxides
oxides
Oxidation
oxidation
Doppler effect
Vacancies
Oxygen
zirconium alloys
Zirconium alloys
oxygen
Zirconium
Density functional theory
cracks
Spectroscopy
density functional theory
Cracks
Defects
cycles

Keywords

  • Doppler broadening
  • Positron annihilation spectroscopy
  • Zirconium oxidation

Cite this

Heikinheimo, J. ; Ortner, S. ; Makkonen, I. ; Kujala, J. ; Blackmur, M. ; Tuomisto, F. / Positron annihilation analysis of the atomic scale changes in oxidized Zircaloy-4 samples. In: Journal of Nuclear Materials. 2017 ; Vol. 495. pp. 172-180.
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Positron annihilation analysis of the atomic scale changes in oxidized Zircaloy-4 samples. / Heikinheimo, J.; Ortner, S.; Makkonen, I.; Kujala, J.; Blackmur, M.; Tuomisto, F.

In: Journal of Nuclear Materials, Vol. 495, 11.2017, p. 172-180.

Research output: Contribution to journalArticleScientificpeer-review

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AU - Heikinheimo, J.

AU - Ortner, S.

AU - Makkonen, I.

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AU - Blackmur, M.

AU - Tuomisto, F.

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AB - The process of oxidation in zirconium alloys is not straightforward. It includes cyclic periods, where the oxidation rate is decelerating as a function of increasing oxide thickness. Transition to the higher oxidation rate happens approximately after every 2 μm oxide growth and each cycle is associated with a layer of oxide with little or no cracking and a similar thickness layer with a large number of micro-scale lateral cracks. This work uses positron annihilation Doppler broadening spectroscopy to investigate the development of atomic-scale defect features in the oxides on Zircaloy-4 samples exposed to alkaline water at 350 °C. Results from the Doppler broadening measurements supported by Density Functional Theory calculations indicate that complexes involving both zirconium-site and oxygen-site vacancies exist in the oxide. The implications of the vacancies in the oxide layer are considered for oxygen diffusion and the oxidation rate.

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