Understanding the effect of specimen size on the properties of fine-grain isotropic nuclear graphite for irradiation studies: Mechanical properties

Anne A. Campbell; Andrew A. Wereszczak; Mary A. Snead; Yutai Katoh

doi:10.1016/j.jnucmat.2023.154263

Understanding the effect of specimen size on the properties of fine-grain isotropic nuclear graphite for irradiation studies: Mechanical properties

Anne A. Campbell, Andrew A. Wereszczak, Mary A. Snead, Yutai Katoh

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

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Abstract

Programs at Oak Ridge National Laboratory are investigating the effects of neutron irradiation in the High Flux Isotope Reactor (HFIR) on properties of fine-grain isotropic nuclear graphites. Specimens were irradiated in the HFIR flux trap, which requires using specimens that are smaller than the sizes recommended by ASTM standards. This work has investigated whether subsized specimens can be used to reliably predict strength behavior. The results show that (1) tensile strength was loosely coupled to specimen volume, (2) the compression specimens had a slightly higher strength for larger volumes, (3) the uniaxial flexural strength was nearly independent of specimen effective area for one orientation whereas the other orientation showed a slight strength–size scaling Weibull behavior, and (4) equibiaxial flexural strength followed traditional strength–size scaling Weibull behavior. These results suggest that fine-grain graphite is more similar to ceramics than to medium- and large-grained graphite with respect to both the strength-limiting flaws (Griffith theory) and the effect of machining on the strength behavior. This work shows that using specimens that are smaller than ASTM recommendations are suitable for investigating the strength changes caused by neutron irradiation because the primary interest is the relative change in the strength distribution parameters rather than their absolute values.

Original language	English
Article number	154263
Journal	Journal of Nuclear Materials
Volume	576
DOIs	https://doi.org/10.1016/j.jnucmat.2023.154263
State	Published - Apr 1 2023

Funding

Oak Ridge National Laboratory is managed by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 for the US Department of Energy. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05–00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US 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 US government purposes. 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 ). This research was performed at the Oak Ridge National Laboratory (ORNL) and sponsored by Tokai Carbon Co. Ltd. under the Material Science and Technology Division, Work-for-Others (WFO) Program, IAN: 16B630901, and DOE agreement: NFE-09-02345, Toyo Tanso Co. Ltd. under the Material Science and Technology Division, Work-for-Others (WFO) Program, IAN: 16B654401, and DOE agreement: NFE-10-02974, IBIDEN Co. Ltd. under the Material Science and Technology Division, Work-for-Others (WFO) Program, IAN: 16B667001, and DOE agreement: NFE-11-03389, and Nippon Steel Chemical – Nippon Carbon Group ( NSCC NCK Group) under the Material Science and Technology Division, Work-for-Others (WFO) Program, IAN: 16B680601, and DOE agreement: NFE-12-03865, all with the US Department of Energy.

Funders	Funder number
IBIDEN Co. Ltd.	NFE-11-03389, 16B667001
Nippon Steel Chemical – Nippon Carbon Group
Tokai Carbon Co. Ltd.	16B630901
Toyo Tanso Co. Ltd.	16B654401, NFE-10-02974
U.S. Department of Energy	NFE-09-02345
Oak Ridge National Laboratory
UT-Battelle	DE-AC05–00OR22725
National Supercomputer Centre in Guangzhou	16B680601, NFE-12-03865

Keywords

Graphite
Neutron irradiation effects
Strength

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10.1016/j.jnucmat.2023.154263

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title = "Understanding the effect of specimen size on the properties of fine-grain isotropic nuclear graphite for irradiation studies: Mechanical properties",

abstract = "Programs at Oak Ridge National Laboratory are investigating the effects of neutron irradiation in the High Flux Isotope Reactor (HFIR) on properties of fine-grain isotropic nuclear graphites. Specimens were irradiated in the HFIR flux trap, which requires using specimens that are smaller than the sizes recommended by ASTM standards. This work has investigated whether subsized specimens can be used to reliably predict strength behavior. The results show that (1) tensile strength was loosely coupled to specimen volume, (2) the compression specimens had a slightly higher strength for larger volumes, (3) the uniaxial flexural strength was nearly independent of specimen effective area for one orientation whereas the other orientation showed a slight strength–size scaling Weibull behavior, and (4) equibiaxial flexural strength followed traditional strength–size scaling Weibull behavior. These results suggest that fine-grain graphite is more similar to ceramics than to medium- and large-grained graphite with respect to both the strength-limiting flaws (Griffith theory) and the effect of machining on the strength behavior. This work shows that using specimens that are smaller than ASTM recommendations are suitable for investigating the strength changes caused by neutron irradiation because the primary interest is the relative change in the strength distribution parameters rather than their absolute values.",

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Understanding the effect of specimen size on the properties of fine-grain isotropic nuclear graphite for irradiation studies: Mechanical properties

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