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

doi:10.1016/j.jnucmat.2017.08.004

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

^*Corresponding author for this work

Not published at VTT

Aalto University
Culham Science Centre

Research output: Contribution to journal › Article › Scientific › peer-review

13 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 language	English
Pages (from-to)	172-180
Number of pages	9
Journal	Journal of Nuclear Materials
Volume	495
DOIs	https://doi.org/10.1016/j.jnucmat.2017.08.004
Publication status	Published - Nov 2017
MoE publication type	A1 Journal article-refereed

Funding

We acknowledge the computational resources provided by the Aalto Science-IT project and CSC - the Finnish IT Center for Science. We also thank Amec Foster Wheeler for their support and the provision of samples. IM acknowledges financial support from the Academy of Finland (projects 285809 and 293932).

Keywords

Doppler broadening
Positron annihilation spectroscopy
Zirconium oxidation

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10.1016/j.jnucmat.2017.08.004

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title = "Positron annihilation analysis of the atomic scale changes in oxidized Zircaloy-4 samples",

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.",

keywords = "Doppler broadening, Positron annihilation spectroscopy, Zirconium oxidation",

author = "J. Heikinheimo and S. Ortner and I. Makkonen and J. Kujala and M. Blackmur and F. Tuomisto",

note = "Funding Information: We acknowledge the computational resources provided by the Aalto Science-IT project and CSC - the Finnish IT Center for Science. We also thank Amec Foster Wheeler for their support and the provision of samples. IM acknowledges financial support from the Academy of Finland (projects 285809 and 293932 ). Funding Information: We acknowledge the computational resources provided by the Aalto Science-IT project and CSC - the Finnish IT Center for Science. We also thank Amec Foster Wheeler for their support and the provision of samples. IM acknowledges financial support from the Academy of Finland (projects 285809 and 293932). Publisher Copyright: {\textcopyright} 2017 Elsevier B.V. Copyright: Copyright 2017 Elsevier B.V., All rights reserved.",

year = "2017",

month = nov,

doi = "10.1016/j.jnucmat.2017.08.004",

language = "English",

volume = "495",

pages = "172--180",

journal = "Journal of Nuclear Materials",

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T1 - Positron annihilation analysis of the atomic scale changes in oxidized Zircaloy-4 samples

AU - Heikinheimo, J.

AU - Ortner, S.

AU - Makkonen, I.

AU - Kujala, J.

AU - Blackmur, M.

AU - Tuomisto, F.

N1 - Funding Information: We acknowledge the computational resources provided by the Aalto Science-IT project and CSC - the Finnish IT Center for Science. We also thank Amec Foster Wheeler for their support and the provision of samples. IM acknowledges financial support from the Academy of Finland (projects 285809 and 293932 ). Funding Information: We acknowledge the computational resources provided by the Aalto Science-IT project and CSC - the Finnish IT Center for Science. We also thank Amec Foster Wheeler for their support and the provision of samples. IM acknowledges financial support from the Academy of Finland (projects 285809 and 293932). Publisher Copyright: © 2017 Elsevier B.V. Copyright: Copyright 2017 Elsevier B.V., All rights reserved.

PY - 2017/11

Y1 - 2017/11

N2 - 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.

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.

KW - Doppler broadening

KW - Positron annihilation spectroscopy

KW - Zirconium oxidation

UR - https://www.scopus.com/pages/publications/85027726108

U2 - 10.1016/j.jnucmat.2017.08.004

DO - 10.1016/j.jnucmat.2017.08.004

M3 - Article

AN - SCOPUS:85027726108

SN - 0022-3115

VL - 495

SP - 172

EP - 180

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

ER -

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

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Keywords

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