Equibiaxial Flexure Strength of a Superfine-Grained Nuclear Graphite

Anne A. Campbell; Andrew A. Wereszczak; Josina W. Geringer; Yutai Katoh

doi:10.1520/STP163920210075

Equibiaxial Flexure Strength of a Superfine-Grained Nuclear Graphite

Anne A. Campbell, Andrew A. Wereszczak, Josina W. Geringer, Yutai Katoh

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

3 Scopus citations

Abstract

The strength of advanced graphite is reported in accordance with ASTM D7846-16 using a two-parameter Weibull distribution for uniaxial strength testing. The rule of thumb for Weibull distributions is to use a minimum of 30 strength measurements to have a high level of confidence in the Weibull characteristic strength and the Weibull modulus. These large sample sets for statistical confidence are easily obtained for as-manufactured graphite, but determination of the Weibull two-factor parameters on graphite that has been exposed to neutron irradiation is nearly impossible due to irradiation testing restraints on specimen size and space limitations in test reactors for the accommodation of specimens. These restrictions have resulted in irradiation programs that use sub-sized specimens to measure uniaxial strength change, but the specimen geometries still hinder the number of replicate specimens for each irradiation condition. In contrast, this work used an advanced ceramic standard, ASTM C1499-05, as the foundation for equibiaxial strength testing of a superfine-grained nuclear graphite to investigate the irradiation-induced strength change and any changes to the two-parameter Weibull distribution. The goal was to investigate the effect of specimen size on the two-parameter Weibull distribution parameters in support of the small specimens and geometry desired for irradiation. A study of the effect of a reduced sample population was also undertaken to investigate the reliability of using the two-parameter Weibull distribution to study changes to the materials properties caused by neutron irradiation damage. The results of this work suggest that these equibiaxial specimens would be ideal for statistically significant studies of the effects of irradiation on the Weibull characteristic strength (but not the modulus) and for providing a method for surveillance specimen campaigns for future operating commercial reactors.

Original language	English
Title of host publication	Graphite Testing for Nuclear Applications
Subtitle of host publication	The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments
Editors	Athanasia Tzelepi, Martin Metcalfe
Publisher	ASTM International
Pages	18-33
Number of pages	16
ISBN (Electronic)	9780803177253
DOIs	https://doi.org/10.1520/STP163920210075
State	Published - 2022
Event	2021 Symposium on Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments - Virtual, Online Duration: Sep 23 2021 → Sep 24 2021

Publication series

Name	ASTM Special Technical Publication
Volume	STP 1639
ISSN (Print)	0066-0558

Conference

Conference	2021 Symposium on Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments
City	Virtual, Online
Period	09/23/21 → 09/24/21

Funding

This manuscript has been authored by UT-Battelle LLC under contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy. gov/downloads/doe-public-access-plan). The authors wish to acknowledge Chunghao Shih for performance of the strength testing. This research was performed at Oak Ridge National Laboratory and sponsored by IBIDEN Co., Ltd. (NFE-11-03389) and the Advanced Reactor Technologies program of the U.S. Department of Energy. Oak Ridge National Laboratory is managed by UT-Battelle LLC under contract number DE-AC05-00OR22725 for the U.S. Department of Energy.

Funders	Funder number
Ibiden Co., Ltd.	NFE-11-03389
U.S. Department of Energy
Oak Ridge National Laboratory
UT-Battelle	DE-AC05-00OR22725

Keywords

equibiaxial strength
graphite
strength testing

Access to Document

10.1520/STP163920210075

Cite this

Campbell, A. A., Wereszczak, A. A., Geringer, J. W., & Katoh, Y. (2022). Equibiaxial Flexure Strength of a Superfine-Grained Nuclear Graphite. In A. Tzelepi, & M. Metcalfe (Eds.), Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments (pp. 18-33). (ASTM Special Technical Publication; Vol. STP 1639). ASTM International. https://doi.org/10.1520/STP163920210075

Campbell, Anne A. ; Wereszczak, Andrew A. ; Geringer, Josina W. et al. / Equibiaxial Flexure Strength of a Superfine-Grained Nuclear Graphite. Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments. editor / Athanasia Tzelepi ; Martin Metcalfe. ASTM International, 2022. pp. 18-33 (ASTM Special Technical Publication).

@inproceedings{537027b64d8845bfb276a679ee6d3486,

title = "Equibiaxial Flexure Strength of a Superfine-Grained Nuclear Graphite",

abstract = "The strength of advanced graphite is reported in accordance with ASTM D7846-16 using a two-parameter Weibull distribution for uniaxial strength testing. The rule of thumb for Weibull distributions is to use a minimum of 30 strength measurements to have a high level of confidence in the Weibull characteristic strength and the Weibull modulus. These large sample sets for statistical confidence are easily obtained for as-manufactured graphite, but determination of the Weibull two-factor parameters on graphite that has been exposed to neutron irradiation is nearly impossible due to irradiation testing restraints on specimen size and space limitations in test reactors for the accommodation of specimens. These restrictions have resulted in irradiation programs that use sub-sized specimens to measure uniaxial strength change, but the specimen geometries still hinder the number of replicate specimens for each irradiation condition. In contrast, this work used an advanced ceramic standard, ASTM C1499-05, as the foundation for equibiaxial strength testing of a superfine-grained nuclear graphite to investigate the irradiation-induced strength change and any changes to the two-parameter Weibull distribution. The goal was to investigate the effect of specimen size on the two-parameter Weibull distribution parameters in support of the small specimens and geometry desired for irradiation. A study of the effect of a reduced sample population was also undertaken to investigate the reliability of using the two-parameter Weibull distribution to study changes to the materials properties caused by neutron irradiation damage. The results of this work suggest that these equibiaxial specimens would be ideal for statistically significant studies of the effects of irradiation on the Weibull characteristic strength (but not the modulus) and for providing a method for surveillance specimen campaigns for future operating commercial reactors.",

keywords = "equibiaxial strength, graphite, strength testing",

author = "Campbell, {Anne A.} and Wereszczak, {Andrew A.} and Geringer, {Josina W.} and Yutai Katoh",

note = "Publisher Copyright: {\textcopyright} 2022 ASTM International. All rights reserved.; 2021 Symposium on Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments ; Conference date: 23-09-2021 Through 24-09-2021",

year = "2022",

doi = "10.1520/STP163920210075",

language = "English",

series = "ASTM Special Technical Publication",

publisher = "ASTM International",

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editor = "Athanasia Tzelepi and Martin Metcalfe",

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Campbell, AA , Wereszczak, AA, Geringer, JW & Katoh, Y 2022, Equibiaxial Flexure Strength of a Superfine-Grained Nuclear Graphite. in A Tzelepi & M Metcalfe (eds), Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments. ASTM Special Technical Publication, vol. STP 1639, ASTM International, pp. 18-33, 2021 Symposium on Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments, Virtual, Online, 09/23/21. https://doi.org/10.1520/STP163920210075

Equibiaxial Flexure Strength of a Superfine-Grained Nuclear Graphite. / Campbell, Anne A.; Wereszczak, Andrew A.; Geringer, Josina W. et al.
Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments. ed. / Athanasia Tzelepi; Martin Metcalfe. ASTM International, 2022. p. 18-33 (ASTM Special Technical Publication; Vol. STP 1639).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

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AU - Katoh, Yutai

PY - 2022

Y1 - 2022

N2 - The strength of advanced graphite is reported in accordance with ASTM D7846-16 using a two-parameter Weibull distribution for uniaxial strength testing. The rule of thumb for Weibull distributions is to use a minimum of 30 strength measurements to have a high level of confidence in the Weibull characteristic strength and the Weibull modulus. These large sample sets for statistical confidence are easily obtained for as-manufactured graphite, but determination of the Weibull two-factor parameters on graphite that has been exposed to neutron irradiation is nearly impossible due to irradiation testing restraints on specimen size and space limitations in test reactors for the accommodation of specimens. These restrictions have resulted in irradiation programs that use sub-sized specimens to measure uniaxial strength change, but the specimen geometries still hinder the number of replicate specimens for each irradiation condition. In contrast, this work used an advanced ceramic standard, ASTM C1499-05, as the foundation for equibiaxial strength testing of a superfine-grained nuclear graphite to investigate the irradiation-induced strength change and any changes to the two-parameter Weibull distribution. The goal was to investigate the effect of specimen size on the two-parameter Weibull distribution parameters in support of the small specimens and geometry desired for irradiation. A study of the effect of a reduced sample population was also undertaken to investigate the reliability of using the two-parameter Weibull distribution to study changes to the materials properties caused by neutron irradiation damage. The results of this work suggest that these equibiaxial specimens would be ideal for statistically significant studies of the effects of irradiation on the Weibull characteristic strength (but not the modulus) and for providing a method for surveillance specimen campaigns for future operating commercial reactors.

AB - The strength of advanced graphite is reported in accordance with ASTM D7846-16 using a two-parameter Weibull distribution for uniaxial strength testing. The rule of thumb for Weibull distributions is to use a minimum of 30 strength measurements to have a high level of confidence in the Weibull characteristic strength and the Weibull modulus. These large sample sets for statistical confidence are easily obtained for as-manufactured graphite, but determination of the Weibull two-factor parameters on graphite that has been exposed to neutron irradiation is nearly impossible due to irradiation testing restraints on specimen size and space limitations in test reactors for the accommodation of specimens. These restrictions have resulted in irradiation programs that use sub-sized specimens to measure uniaxial strength change, but the specimen geometries still hinder the number of replicate specimens for each irradiation condition. In contrast, this work used an advanced ceramic standard, ASTM C1499-05, as the foundation for equibiaxial strength testing of a superfine-grained nuclear graphite to investigate the irradiation-induced strength change and any changes to the two-parameter Weibull distribution. The goal was to investigate the effect of specimen size on the two-parameter Weibull distribution parameters in support of the small specimens and geometry desired for irradiation. A study of the effect of a reduced sample population was also undertaken to investigate the reliability of using the two-parameter Weibull distribution to study changes to the materials properties caused by neutron irradiation damage. The results of this work suggest that these equibiaxial specimens would be ideal for statistically significant studies of the effects of irradiation on the Weibull characteristic strength (but not the modulus) and for providing a method for surveillance specimen campaigns for future operating commercial reactors.

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Campbell AA , Wereszczak AA, Geringer JW, Katoh Y. Equibiaxial Flexure Strength of a Superfine-Grained Nuclear Graphite. In Tzelepi A, Metcalfe M, editors, Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments. ASTM International. 2022. p. 18-33. (ASTM Special Technical Publication). doi: 10.1520/STP163920210075

Equibiaxial Flexure Strength of a Superfine-Grained Nuclear Graphite

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