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Title: Microbeam X-Ray Absorption Near-Edge Spectroscopy of Alloying Elements in the Oxide Layers of Irradiated Zircaloy-2

Abstract

Hydrogen pickup of zirconium-based fuel cladding and structural materials during in-reactor corrosion can degrade fuel components because the ingress of hydrogen can lead to the formation of brittle hydrides. In the boiling water reactor (BWR) environment, Zircaloy-2 fuel cladding and structural components such as water rods and channels can experience accelerated hydrogen pickup, whereas Zircaloy-4 components exposed to similar conditions do not. Because the principal difference between the two alloys is that Zircaloy-2 contains nickel, accelerated hydrogen pickup has been hypothesized to result from the presence of nickel. However, an understanding of the mechanism by which this acceleration occurs is still lacking. We investigated the link between hydrogen pickup and the oxidation behavior of alloying elements when incorporated into the oxide layers formed on zirconium alloys when corroded in the reactor. Synchrotron radiation microbeam X-ray absorption near-edge spectroscopy (XANES) at the Advanced Photon Source was performed on carefully selected BWR-corroded Zircaloy-2 water rods at an assembly-averaged burnup ranging from 32.8 to 74.6 GWd/MTU to determine the oxidation states of alloying elements, such as iron and nickel, within the oxide layers as a function of distance from the oxide-metal interface at high burnup. Samples were chosen for comparison based on havingmore » similar oxide thicknesses, processing, elevation, reactors, and fluences but different hydrogen pickup fractions. Examinations of the oxide layers formed on these samples showed that (1) the oxidation states of these alloying elements changed with distance from the oxide-metal interface, (2) these elements exhibited delayed oxidation relative to the host zirconium, and (3) nickel in Zircaloy-2 remained metallic in the oxide layer at a longer distance from the oxide-metal interface than iron. An analysis of these results showed an apparent correlation between the delayed oxidation of nickel and higher hydrogen pickup of Zircaloy-2 at high burnup.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1468942
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Conference: 18th International Symposium on Zirconium in the Nuclear Industry, 05/15/16 - 05/19/16, Hilton Head, SC, US
Country of Publication:
United States
Language:
English
Subject:
XANES; alloying elements; high burn-up; hydrogen pick-up; oxidation state; zircaloy-2

Citation Formats

Shivprasad, Aditya P., Motta, Arthur T., Kucuk, Aylin, Yagnik, Suresh, and Cai, Zhonghou. Microbeam X-Ray Absorption Near-Edge Spectroscopy of Alloying Elements in the Oxide Layers of Irradiated Zircaloy-2. United States: N. p., 2018. Web. doi:10.1520/STP159720160076.
Shivprasad, Aditya P., Motta, Arthur T., Kucuk, Aylin, Yagnik, Suresh, & Cai, Zhonghou. Microbeam X-Ray Absorption Near-Edge Spectroscopy of Alloying Elements in the Oxide Layers of Irradiated Zircaloy-2. United States. doi:10.1520/STP159720160076.
Shivprasad, Aditya P., Motta, Arthur T., Kucuk, Aylin, Yagnik, Suresh, and Cai, Zhonghou. Mon . "Microbeam X-Ray Absorption Near-Edge Spectroscopy of Alloying Elements in the Oxide Layers of Irradiated Zircaloy-2". United States. doi:10.1520/STP159720160076. https://www.osti.gov/servlets/purl/1468942.
@article{osti_1468942,
title = {Microbeam X-Ray Absorption Near-Edge Spectroscopy of Alloying Elements in the Oxide Layers of Irradiated Zircaloy-2},
author = {Shivprasad, Aditya P. and Motta, Arthur T. and Kucuk, Aylin and Yagnik, Suresh and Cai, Zhonghou},
abstractNote = {Hydrogen pickup of zirconium-based fuel cladding and structural materials during in-reactor corrosion can degrade fuel components because the ingress of hydrogen can lead to the formation of brittle hydrides. In the boiling water reactor (BWR) environment, Zircaloy-2 fuel cladding and structural components such as water rods and channels can experience accelerated hydrogen pickup, whereas Zircaloy-4 components exposed to similar conditions do not. Because the principal difference between the two alloys is that Zircaloy-2 contains nickel, accelerated hydrogen pickup has been hypothesized to result from the presence of nickel. However, an understanding of the mechanism by which this acceleration occurs is still lacking. We investigated the link between hydrogen pickup and the oxidation behavior of alloying elements when incorporated into the oxide layers formed on zirconium alloys when corroded in the reactor. Synchrotron radiation microbeam X-ray absorption near-edge spectroscopy (XANES) at the Advanced Photon Source was performed on carefully selected BWR-corroded Zircaloy-2 water rods at an assembly-averaged burnup ranging from 32.8 to 74.6 GWd/MTU to determine the oxidation states of alloying elements, such as iron and nickel, within the oxide layers as a function of distance from the oxide-metal interface at high burnup. Samples were chosen for comparison based on having similar oxide thicknesses, processing, elevation, reactors, and fluences but different hydrogen pickup fractions. Examinations of the oxide layers formed on these samples showed that (1) the oxidation states of these alloying elements changed with distance from the oxide-metal interface, (2) these elements exhibited delayed oxidation relative to the host zirconium, and (3) nickel in Zircaloy-2 remained metallic in the oxide layer at a longer distance from the oxide-metal interface than iron. An analysis of these results showed an apparent correlation between the delayed oxidation of nickel and higher hydrogen pickup of Zircaloy-2 at high burnup.},
doi = {10.1520/STP159720160076},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {1}
}

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