TY - GEN
T1 - Performance of Graphite Oxidation with Environment and Specimen Geometry Variations
AU - Smith, Rebecca E.
AU - Windes, William
N1 - Funding Information:
We would like to thank Austin Matthews of Idaho National Laboratory for his assistance with oxidation testing and analysis, as well as Joshua Kane of Idaho National Laboratory and Cristian Contescu of Oak Ridge National Laboratory for sharing many insights into graphite oxidation behavior. We gratefully acknowledge that funding for this work was provided by the U.S. Department of Energy’s Advanced Reactor Technologies Program under the DOE Idaho Operations Office, Contract DE-AC07-05ID14517, with Battelle Energy Alliance, LLC.
Publisher Copyright:
Copyright 2022 by ASTM International.
PY - 2022/12/1
Y1 - 2022/12/1
N2 - For oxidation data from diverse studies to be compared and applied to nuclear graphite degradation behavior, all testing must quantify the oxidation rate as a material-specific property under tightly controlled test conditions. Graphite oxidation behavior is affected by a wide range of parameter variations beyond graphite grade and oxidation temperature. ASTM D7542-15 attempts to control the graphite oxidation with specific furnace dimensions and careful test parameters designed to establish surplus oxygen conditions over a limited temperature range. Practical constraints for relating the observed oxidation of the standardized test sample size to smaller sample geometries must be considered along with the testing conditions to enforce an intrinsic, or material-specific, response. Similarly, these same test parameters must be examined when altering the oxidizing furnace (i.e., oxidizing within a thermogravimetric analyzer [TGA]) to ensure consistent intrinsic response rather than responding to the extrinsic test conditions. Here, data are presented from both vertical furnace and TGA experiments. Substantial differences in sample dimensions and geometric proportions require substantial verification of the test conditions. Because these variations can influence oxygen availability, the presence of excess oxygen must be confirmed to validate the range of conditions over which the data from disparate oxidizing systems can be compared. Statistical reproduction of testing over a suitable range of parameters appears to be more important than accommodating larger specimens, competing priorities that are particularly challenging for irradiated materials. The major considerations addressed are oxygen supply (partial pressure, gas flow, availability at the interface), specimen dimensions and purity, grade-specific microstructural effects (mass loss progression, oxidation penetration, and density gradient evolution), concurrent with temperature effects for tested conditions.
AB - For oxidation data from diverse studies to be compared and applied to nuclear graphite degradation behavior, all testing must quantify the oxidation rate as a material-specific property under tightly controlled test conditions. Graphite oxidation behavior is affected by a wide range of parameter variations beyond graphite grade and oxidation temperature. ASTM D7542-15 attempts to control the graphite oxidation with specific furnace dimensions and careful test parameters designed to establish surplus oxygen conditions over a limited temperature range. Practical constraints for relating the observed oxidation of the standardized test sample size to smaller sample geometries must be considered along with the testing conditions to enforce an intrinsic, or material-specific, response. Similarly, these same test parameters must be examined when altering the oxidizing furnace (i.e., oxidizing within a thermogravimetric analyzer [TGA]) to ensure consistent intrinsic response rather than responding to the extrinsic test conditions. Here, data are presented from both vertical furnace and TGA experiments. Substantial differences in sample dimensions and geometric proportions require substantial verification of the test conditions. Because these variations can influence oxygen availability, the presence of excess oxygen must be confirmed to validate the range of conditions over which the data from disparate oxidizing systems can be compared. Statistical reproduction of testing over a suitable range of parameters appears to be more important than accommodating larger specimens, competing priorities that are particularly challenging for irradiated materials. The major considerations addressed are oxygen supply (partial pressure, gas flow, availability at the interface), specimen dimensions and purity, grade-specific microstructural effects (mass loss progression, oxidation penetration, and density gradient evolution), concurrent with temperature effects for tested conditions.
KW - acute oxidation
KW - advanced reactor
KW - kinetic regime
KW - nuclear graphite
KW - testing
UR - http://www.scopus.com/inward/record.url?scp=85168887959&partnerID=8YFLogxK
UR - https://www.mendeley.com/catalogue/6582383d-7ac8-3dc1-b093-78db4dd0cdae/
U2 - 10.1520/STP163920210134
DO - 10.1520/STP163920210134
M3 - Conference contribution
AN - SCOPUS:85168887959
SN - 9780803177253
T3 - ASTM Special Technical Publication
SP - 279
EP - 303
BT - Graphite Testing for Nuclear Applications
A2 - Tzelepi, Athanasia
A2 - Metcalfe, Martin
PB - ASTM International
T2 - 2021 Symposium on Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments
Y2 - 23 September 2021 through 24 September 2021
ER -