Microstructural analysis of tristructural isotropic particles in high-temperature steam mixed gas atmospheres

Katherine I. Montoya; Brian A. Brigham; Grant Helmreich; Jesse Werden; Tyler J. Gerczak; Elizabeth S. Sooby

doi:10.1016/j.jnucmat.2023.154385

Microstructural analysis of tristructural isotropic particles in high-temperature steam mixed gas atmospheres

Katherine I. Montoya, Brian A. Brigham, Grant Helmreich, Jesse Werden, Tyler J. Gerczak, Elizabeth S. Sooby

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

2 Scopus citations

Abstract

High-temperature gas-cooled reactors (HTGRs) use tristructural isotropic (TRISO) particles embedded in a graphitic matrix material to form the integral fuel element. Potential off-normal reactor conditions for HTGRs include steam ingress with temperatures above 1,000 °C. Fuel element exposure to steam can cause the graphitic matrix material to evolve, forming an atmosphere composed of oxidants and oxidation products and potentially exposing the TRISO particles to these conditions. Investigating the oxidation response of TRISO particles exposed to a mixed gas atmosphere will provide insight into the stability under off-normal conditions. In this study, surrogate TRISO particles were exposed to high temperatures (T = 1,200 °C) in flowing steam (3% < pH₂O < 21%) and CO (pCO < 1%) to determine the oxidation behavior of the SiC layer when exposed to various mixed gas atmospheres. Scanning electron microscopy, x-ray diffraction, and focused ion beam milling was used to determine the impact of CO and steam on the oxidation behavior of the SiC layer. The data presented demonstrates how the SiC layer showed strong oxidation resistance due to limited SiO₂ growth and maintained its structural integrity under these off-normal conditions.

Original language	English
Article number	154385
Journal	Journal of Nuclear Materials
Volume	579
DOIs	https://doi.org/10.1016/j.jnucmat.2023.154385
State	Published - Jun 2023

Funding

FIB microscopic measurements were taken in the Low Activation Materials and Development and Analysis facilities at Oak Ridge National Laboratory. Ion milling cross-sectioning was performed at the University of Texas at San Antonio Kleberg Advanced Microscopy Center with the support of Hitachi High-Tech. Materials for this work were provided by the US Department of Energy's (DOE's) Office of Nuclear Energy Advanced Reactor Technologies as part of the Advanced Gas Reactor Fuel Development and Qualification (AGR) program. This material is based upon work supported by the U.S. Department of Energy, Office of Nuclear Energy AGR Program, ORISE H.E.R.E Program, and Department of Energy Nuclear Energy University Programs. Award Number: DE-NE0008798. FIB microscopic measurements were taken in the Low Activation Materials and Development and Analysis facilities at Oak Ridge National Laboratory. Ion milling cross-sectioning was performed at the University of Texas at San Antonio Kleberg Advanced Microscopy Center with the support of Hitachi High-Tech. Materials for this work were provided by the US Department of Energy's (DOE's) Office of Nuclear Energy Advanced Reactor Technologies as part of the Advanced Gas Reactor Fuel Development and Qualification (AGR) program. This material is based upon work supported by the U.S. Department of Energy , Office of Nuclear Energy AGR Program, ORISE H.E.R.E Program, and Department of Energy Nuclear Energy University Programs. Award Number: DE-NE0008798.

Keywords

High-temperature gas reactor
Ion milling techniques
Nuclear fuel
Silicon carbide
Steam oxidation
TRISO

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10.1016/j.jnucmat.2023.154385

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title = "Microstructural analysis of tristructural isotropic particles in high-temperature steam mixed gas atmospheres",

abstract = "High-temperature gas-cooled reactors (HTGRs) use tristructural isotropic (TRISO) particles embedded in a graphitic matrix material to form the integral fuel element. Potential off-normal reactor conditions for HTGRs include steam ingress with temperatures above 1,000 °C. Fuel element exposure to steam can cause the graphitic matrix material to evolve, forming an atmosphere composed of oxidants and oxidation products and potentially exposing the TRISO particles to these conditions. Investigating the oxidation response of TRISO particles exposed to a mixed gas atmosphere will provide insight into the stability under off-normal conditions. In this study, surrogate TRISO particles were exposed to high temperatures (T = 1,200 °C) in flowing steam (3% < pH2O < 21%) and CO (pCO < 1%) to determine the oxidation behavior of the SiC layer when exposed to various mixed gas atmospheres. Scanning electron microscopy, x-ray diffraction, and focused ion beam milling was used to determine the impact of CO and steam on the oxidation behavior of the SiC layer. The data presented demonstrates how the SiC layer showed strong oxidation resistance due to limited SiO2 growth and maintained its structural integrity under these off-normal conditions.",

keywords = "High-temperature gas reactor, Ion milling techniques, Nuclear fuel, Silicon carbide, Steam oxidation, TRISO",

author = "Montoya, {Katherine I.} and Brigham, {Brian A.} and Grant Helmreich and Jesse Werden and Gerczak, {Tyler J.} and Sooby, {Elizabeth S.}",

note = "Publisher Copyright: {\textcopyright} 2023",

year = "2023",

month = jun,

doi = "10.1016/j.jnucmat.2023.154385",

language = "English",

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AU - Montoya, Katherine I.

AU - Brigham, Brian A.

AU - Helmreich, Grant

AU - Werden, Jesse

AU - Gerczak, Tyler J.

AU - Sooby, Elizabeth S.

PY - 2023/6

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N2 - High-temperature gas-cooled reactors (HTGRs) use tristructural isotropic (TRISO) particles embedded in a graphitic matrix material to form the integral fuel element. Potential off-normal reactor conditions for HTGRs include steam ingress with temperatures above 1,000 °C. Fuel element exposure to steam can cause the graphitic matrix material to evolve, forming an atmosphere composed of oxidants and oxidation products and potentially exposing the TRISO particles to these conditions. Investigating the oxidation response of TRISO particles exposed to a mixed gas atmosphere will provide insight into the stability under off-normal conditions. In this study, surrogate TRISO particles were exposed to high temperatures (T = 1,200 °C) in flowing steam (3% < pH2O < 21%) and CO (pCO < 1%) to determine the oxidation behavior of the SiC layer when exposed to various mixed gas atmospheres. Scanning electron microscopy, x-ray diffraction, and focused ion beam milling was used to determine the impact of CO and steam on the oxidation behavior of the SiC layer. The data presented demonstrates how the SiC layer showed strong oxidation resistance due to limited SiO2 growth and maintained its structural integrity under these off-normal conditions.

AB - High-temperature gas-cooled reactors (HTGRs) use tristructural isotropic (TRISO) particles embedded in a graphitic matrix material to form the integral fuel element. Potential off-normal reactor conditions for HTGRs include steam ingress with temperatures above 1,000 °C. Fuel element exposure to steam can cause the graphitic matrix material to evolve, forming an atmosphere composed of oxidants and oxidation products and potentially exposing the TRISO particles to these conditions. Investigating the oxidation response of TRISO particles exposed to a mixed gas atmosphere will provide insight into the stability under off-normal conditions. In this study, surrogate TRISO particles were exposed to high temperatures (T = 1,200 °C) in flowing steam (3% < pH2O < 21%) and CO (pCO < 1%) to determine the oxidation behavior of the SiC layer when exposed to various mixed gas atmospheres. Scanning electron microscopy, x-ray diffraction, and focused ion beam milling was used to determine the impact of CO and steam on the oxidation behavior of the SiC layer. The data presented demonstrates how the SiC layer showed strong oxidation resistance due to limited SiO2 growth and maintained its structural integrity under these off-normal conditions.

KW - High-temperature gas reactor

KW - Ion milling techniques

KW - Nuclear fuel

KW - Silicon carbide

KW - Steam oxidation

KW - TRISO

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Microstructural analysis of tristructural isotropic particles in high-temperature steam mixed gas atmospheres

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