Comparison of unirradiated and irradiated AGR-2 TRISO fuel particle oxidation response

Darren J. Skitt; Rachel L. Seibert; Tyler J. Gerczak; Grant W. Helmreich; Zachary M. Burns; John D. Hunn

doi:10.1016/j.jnucmat.2023.154409

Comparison of unirradiated and irradiated AGR-2 TRISO fuel particle oxidation response

Darren J. Skitt, Rachel L. Seibert, Tyler J. Gerczak, Grant W. Helmreich, Zachary M. Burns, John D. Hunn

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

Abstract

The silicon carbide (SiC) coating in a tristructural isotropic (TRISO) particle acts as a barrier to fission product release during reactor operation and accident scenarios. Oxidation and subsequent failure of the SiC layer during a rare air ingress event is a proposed mechanism for fission product release in a high-temperature gas-cooled reactor (HTGR). Although previous oxidation studies have analyzed unirradiated TRISO particle response, this study compared the oxidation behavior of irradiated and unirradiated TRISO particles from the second Advanced Gas Reactor Fuel Development and Qualification Program irradiation experiment (AGR-2). Particles with exposed SiC were subjected to six varying oxidizing tests in the Furnace for Irradiated TRISO Testing (FITT), examined for failure fraction with the Irradiated Microsphere Gamma Analyzer (IMGA) and characterized with focused ion beam and scanning/transmission electron microscopy techniques to analyze the oxide layer. Uncorrelated unirradiated particle failures throughout the series of exposures suggests that external factors inherent to the experiment increased particle failure sensitivity. However, irradiated particle observations indicated an increased failure response at 400 h 1400 °C in both 2% and 21% O₂ atmospheres above failure associated with external factors. Oxide thickness measurements after 400 h at 1400 °C revealed a greater oxidation rate than predicted by parabolic growth, which was attributed to the increased complexity of the oxide structure at longer exposure times. Altering the atmosphere from 21% to 2% O₂ reduced the average oxide thickness by approximately 12%–14% in both irradiated and unirradiated particles at 400 h 1400 °C. Overall, the minor variations observed between irradiated and unirradiated particles in this study led to the conclusion that unirradiated TRISO particles can be used to approximate irradiated TRISO oxidation kinetics.

Original language	English
Article number	154409
Journal	Journal of Nuclear Materials
Volume	580
DOIs	https://doi.org/10.1016/j.jnucmat.2023.154409
State	Published - Jul 2023

Funding

This work was sponsored by the US Department of Energy Office of Nuclear Energy-Advanced Reactor Technologies as part of the Advanced Gas Reactor Fuel Development and Qualification Program. Hot cell activities were supported by the staff of the ORNL Irradiated Fuels Examination Laboratory. The authors would also like to thank Will Cureton and Peter Doyle at ORNL for providing technical reviews of the paper. Work sponsored by US DEPARTMENT OF ENERGY, Office of Nuclear Energy - as part of the, Advanced Gas Reactor Fuel Development and Qualification Program

Funders	Funder number
Advanced Gas Reactor Fuel Development and Qualification Program
US Department of Energy Office of Nuclear Energy-Advanced Reactor Technologies
U.S. Department of Energy
Office of Nuclear Energy
Oak Ridge National Laboratory

Keywords

High-temperature gas-cooled reactor
Oxidation
Silicon carbide
TRISO

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10.1016/j.jnucmat.2023.154409

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@article{fc3d5672db514c02a986cfae6b33a041,

title = "Comparison of unirradiated and irradiated AGR-2 TRISO fuel particle oxidation response",

abstract = "The silicon carbide (SiC) coating in a tristructural isotropic (TRISO) particle acts as a barrier to fission product release during reactor operation and accident scenarios. Oxidation and subsequent failure of the SiC layer during a rare air ingress event is a proposed mechanism for fission product release in a high-temperature gas-cooled reactor (HTGR). Although previous oxidation studies have analyzed unirradiated TRISO particle response, this study compared the oxidation behavior of irradiated and unirradiated TRISO particles from the second Advanced Gas Reactor Fuel Development and Qualification Program irradiation experiment (AGR-2). Particles with exposed SiC were subjected to six varying oxidizing tests in the Furnace for Irradiated TRISO Testing (FITT), examined for failure fraction with the Irradiated Microsphere Gamma Analyzer (IMGA) and characterized with focused ion beam and scanning/transmission electron microscopy techniques to analyze the oxide layer. Uncorrelated unirradiated particle failures throughout the series of exposures suggests that external factors inherent to the experiment increased particle failure sensitivity. However, irradiated particle observations indicated an increased failure response at 400 h 1400 °C in both 2% and 21% O2 atmospheres above failure associated with external factors. Oxide thickness measurements after 400 h at 1400 °C revealed a greater oxidation rate than predicted by parabolic growth, which was attributed to the increased complexity of the oxide structure at longer exposure times. Altering the atmosphere from 21% to 2% O2 reduced the average oxide thickness by approximately 12%–14% in both irradiated and unirradiated particles at 400 h 1400 °C. Overall, the minor variations observed between irradiated and unirradiated particles in this study led to the conclusion that unirradiated TRISO particles can be used to approximate irradiated TRISO oxidation kinetics.",

keywords = "High-temperature gas-cooled reactor, Oxidation, Silicon carbide, TRISO",

author = "Skitt, {Darren J.} and Seibert, {Rachel L.} and Gerczak, {Tyler J.} and Helmreich, {Grant W.} and Burns, {Zachary M.} and Hunn, {John D.}",

note = "Publisher Copyright: {\textcopyright} 2023 Elsevier B.V.",

year = "2023",

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doi = "10.1016/j.jnucmat.2023.154409",

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volume = "580",

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AU - Skitt, Darren J.

AU - Seibert, Rachel L.

AU - Gerczak, Tyler J.

AU - Helmreich, Grant W.

AU - Burns, Zachary M.

AU - Hunn, John D.

PY - 2023/7

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AB - The silicon carbide (SiC) coating in a tristructural isotropic (TRISO) particle acts as a barrier to fission product release during reactor operation and accident scenarios. Oxidation and subsequent failure of the SiC layer during a rare air ingress event is a proposed mechanism for fission product release in a high-temperature gas-cooled reactor (HTGR). Although previous oxidation studies have analyzed unirradiated TRISO particle response, this study compared the oxidation behavior of irradiated and unirradiated TRISO particles from the second Advanced Gas Reactor Fuel Development and Qualification Program irradiation experiment (AGR-2). Particles with exposed SiC were subjected to six varying oxidizing tests in the Furnace for Irradiated TRISO Testing (FITT), examined for failure fraction with the Irradiated Microsphere Gamma Analyzer (IMGA) and characterized with focused ion beam and scanning/transmission electron microscopy techniques to analyze the oxide layer. Uncorrelated unirradiated particle failures throughout the series of exposures suggests that external factors inherent to the experiment increased particle failure sensitivity. However, irradiated particle observations indicated an increased failure response at 400 h 1400 °C in both 2% and 21% O2 atmospheres above failure associated with external factors. Oxide thickness measurements after 400 h at 1400 °C revealed a greater oxidation rate than predicted by parabolic growth, which was attributed to the increased complexity of the oxide structure at longer exposure times. Altering the atmosphere from 21% to 2% O2 reduced the average oxide thickness by approximately 12%–14% in both irradiated and unirradiated particles at 400 h 1400 °C. Overall, the minor variations observed between irradiated and unirradiated particles in this study led to the conclusion that unirradiated TRISO particles can be used to approximate irradiated TRISO oxidation kinetics.

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VL - 580

JO - Journal of Nuclear Materials

JF - Journal of Nuclear Materials

M1 - 154409

ER -

Comparison of unirradiated and irradiated AGR-2 TRISO fuel particle oxidation response

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