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Title: Neutron Scattering Measurements of Hydrogen Distribution in a Zircaloy-4 Alloy Charged with Hydrogen Gas

Abstract

Neutron incoherent scattering measurements were conducted on Zircaloy-4 round bars. The specimens were charged in a tube furnace at 430 C, using a 12.5 vol. % hydrogen in an argon mixture for 30, 60, and 90 minutes at 13.8 kPa pressure. The volume-average neutron diffraction measurements showed the presence of the face-centered-cubic delta zirconium hydride ({delta}-ZrH{sub 2}) phase in the hydrogenated specimens. The assessment of the background in the diffraction profiles due to the incoherent scattering from the hydrogen atoms was carried out by performing inelastic scans around zero energy transfer and at a fixed two-theta value for which there was only flat background and no coherent scattering. To estimate the relative amount of hydrogen in the Zircaloy-4 samples, the increase in incoherent scattering intensities with hydrogen content was calibrated using samples for which the hydrogen content was known. Measurement of the background scattering from locations within the round bar was also performed to map the distribution of hydrogen content.

Authors:
 [1];  [1];  [1];  [1];  [2];  [2]
  1. ORNL
  2. University of Tennessee, Knoxville (UTK)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Flux Isotope Reactor; High Temperature Materials Laboratory
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
949736
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Science Forum; Journal Volume: 539-543; Journal Issue: n PART 2
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 36 MATERIALS SCIENCE; ALLOYS; ARGON; ATOMS; COHERENT SCATTERING; DIFFRACTION; DISTRIBUTION; ENERGY TRANSFER; FCC LATTICES; FURNACES; HYDROGEN; INCOHERENT SCATTERING; MIXTURES; NEUTRON DIFFRACTION; NEUTRONS; SCATTERING; ZIRCALOY 4; ZIRCONIUM HYDRIDES

Citation Formats

Garlea, Elena, Garlea, Vasile O, Choo, Hahn, Hubbard, Camden R, Liaw, Peter K, and Rack, P. D.. Neutron Scattering Measurements of Hydrogen Distribution in a Zircaloy-4 Alloy Charged with Hydrogen Gas. United States: N. p., 2007. Web. doi:10.4028/www.scientific.net/MSF.539-543.1443.
Garlea, Elena, Garlea, Vasile O, Choo, Hahn, Hubbard, Camden R, Liaw, Peter K, & Rack, P. D.. Neutron Scattering Measurements of Hydrogen Distribution in a Zircaloy-4 Alloy Charged with Hydrogen Gas. United States. doi:10.4028/www.scientific.net/MSF.539-543.1443.
Garlea, Elena, Garlea, Vasile O, Choo, Hahn, Hubbard, Camden R, Liaw, Peter K, and Rack, P. D.. Mon . "Neutron Scattering Measurements of Hydrogen Distribution in a Zircaloy-4 Alloy Charged with Hydrogen Gas". United States. doi:10.4028/www.scientific.net/MSF.539-543.1443.
@article{osti_949736,
title = {Neutron Scattering Measurements of Hydrogen Distribution in a Zircaloy-4 Alloy Charged with Hydrogen Gas},
author = {Garlea, Elena and Garlea, Vasile O and Choo, Hahn and Hubbard, Camden R and Liaw, Peter K and Rack, P. D.},
abstractNote = {Neutron incoherent scattering measurements were conducted on Zircaloy-4 round bars. The specimens were charged in a tube furnace at 430 C, using a 12.5 vol. % hydrogen in an argon mixture for 30, 60, and 90 minutes at 13.8 kPa pressure. The volume-average neutron diffraction measurements showed the presence of the face-centered-cubic delta zirconium hydride ({delta}-ZrH{sub 2}) phase in the hydrogenated specimens. The assessment of the background in the diffraction profiles due to the incoherent scattering from the hydrogen atoms was carried out by performing inelastic scans around zero energy transfer and at a fixed two-theta value for which there was only flat background and no coherent scattering. To estimate the relative amount of hydrogen in the Zircaloy-4 samples, the increase in incoherent scattering intensities with hydrogen content was calibrated using samples for which the hydrogen content was known. Measurement of the background scattering from locations within the round bar was also performed to map the distribution of hydrogen content.},
doi = {10.4028/www.scientific.net/MSF.539-543.1443},
journal = {Materials Science Forum},
number = n PART 2,
volume = 539-543,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Qualitative and quantitative phase measurements were conducted on Zircaloy-4 round bars using neutron scattering techniques. The mapping through the thickness of the specimens using neutron diffraction showed the presence of the face-centered-cubic delta zirconium hydride ({delta}-ZrH{sub 2}) phase on the surface. To determine the relative amount of hydrogen in the Zircaloy-4 samples, the increase of the incoherent scattering with the hydrogen content was calibrated using standard samples for which the hydrogen content was known.
  • Neutron incoherent scattering measurements were conducted on Zircaloy-4 round bars. The specimens were charged in a tube furnace at 430 C, using a 12.5 vol. % hydrogen in an argon mixture for 30, 60, and 90 minutes at 13.8 kPa pressure. The volume-average neutron diffraction measurements showed the presence of the face-centered-cubic delta zirconium hydride ({delta}.ZrH{sub 2}) phase in the hydrogenated specimens. The assessment of the background in the diffraction profiles due to the incoherent scattering from the hydrogen atoms was carried out by performing inelastic scans around zero energy transfer and at a fixed two-theta value for which theremore » was only flat background and no coherent scattering. To estimate the relative amount of hydrogen in the Zircaloy-4 samples, the increase in incoherent scattering intensities with hydrogen content was calibrated using samples for which the hydrogen content was known. Measurement of the background scattering from locations within the round bar was also performed to map the distribution of hydrogen content.« less
  • In this study, a nondestructive neutron scattering method to precisely measure the hydrogen content in high-temperature steam-oxidized Zircaloy-4 cladding was developed. Zircaloy-4 cladding was used to produce hydrided specimens with hydrogen content up to ≈500 wppm. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentrations were selected for the neutron study. The hydrided samples were then oxidized in steam up to ≈6.0wt. % at 1100°C. Optical microscopy shows that our hydriding procedure results in uniform distribution of circumferential hydrides across the wall thickness,more » and uniform oxide layers were formed on the sample surfaces by the steam oxidation. Small- and wide-angle neutron scattering were simultaneously performed to provide a quick (less than an hour per sample) measurement of the hydrogen content in various types of hydrided and oxidized Zircaloy-4. Our study demonstrates that the hydrogen in pre-oxidized Zircaloy-4 cladding can be measured very accurately by both small- and wide-angle neutron scattering. For steam-oxidized samples, the small-angle neutron scattering is contaminated with coherent scattering from additional structural features induced by the steam oxidation. However, the scattering intensity of the wide-angle neutron scattering increases proportionally with the hydrogen charged in the samples. The hydrogen content and wide-angle neutron scattering intensity are highly linearly correlated for the oxidized cladding samples examined in this work, and can be used to precisely determine the hydrogen content in steam-oxidized Zircaloy-4 samples. Hydrogen contents determined by neutron scattering of oxidation samples were also found to be consistent with the results of chemical analysis within acceptable margins for error.« less
  • The macroscopic stress distribution across a Zircaloy-4 gas tungsten arc weld was measured by time-of-flight neutron diffraction at the SMARTS diffractometer at Los Alamos National Laboratory. The method enabled the measurement of strain for all the available reflections permitted by the rolling texture of the plate and the modified texture in the weld-metal and heat affected zone. A maximum longitudinal stress of 220 {+-} 40 MPa was observed in the weld compared with the 0.2% yield stress of 390 MPa of the plate. A maximum transverse stress of 60 {+-} 40 MPa was observed in the weld. Textures were measuredmore » at the HIPPO diffractometer.« less
  • This experiment was carried out to address the need for overcoming the difficulties encountered in hydrogen analysis by means of plasma emission spectroscopy in atmospheric ambient gas. The result of this study on zircaloy-4 samples from a nuclear power plant demonstrates the possibility of attaining a very sharp emission line from impure hydrogen with a very low background and practical elimination of spectral contamination of hydrogen emission arising from surface water and water vapor in atmospheric ambient gas. This was achieved by employing ultrapure ambient helium gas as well as the proper defocusing of the laser irradiation and a largemore » number of repeated precleaning laser shots at the same spot of the sample surface. Further adjustment of the gating time has led to significant reduction of spectral width and improvement of detection sensitivity to {approx}50 ppm. Finally, a linear calibration curve was also obtained for the zircaloy-4 samples with zero intercept. These results demonstrate the feasibility of this technique for practical in situ and quantitative analysis of hydrogen impurity in zircaloy-4 tubes used in a light water nuclear power plant.« less