Abstract
High-temperature gas-cooled reactors (HTGRs) in operation use tristructural isotropic (TRISO) particles embedded in graphite and carbonized resin matrix to form the fuel element. This graphite matrix material serves as a supportive structural element, heat transfer medium, and neutron moderator. In HTGR designs, fuel compacts are exposed to helium coolant, which facilitates high outlet temperatures (750°C<T<950°C) and subsequently greater thermal efficiency than current commercial power reactors. However, data pertaining to the oxidation resistance of graphite matrix material in HTGR accident or off-normal conditions (<50k kPa pH2O, 800°C<T<1600°C) is limited. In this study, both the oxidation behavior of matrix graphite material and its gas-phase products, including CO, CO2, and H2, are quantified in varied oxidant atmospheres using a coupled thermogravimetric analyzer and mass spectrometer. Oxidation rates reported here for varied steam (H2O [g]) atmospheres are predominantly linear and comparable with literature values in the range of tested temperatures (800–1200°C). Changes in dominant matrix oxidation products from primarily CO to a mixture of CO, CO2, and H2 were observed at higher temperatures (≥1000°C) and steam atmospheres (≥5 kPa pH2O). Kinetic data indicates that there was no shift in oxidation regime with chemical oxidation occurring at all temperatures and H2O (g) atmospheres tested. These data provide insight into the oxidation behavior of graphite matrix material and will inform future testing conditions, notably mixed atmospheric conditions, of HTGR fuel elements.
| Original language | English |
|---|---|
| Article number | 153256 |
| Journal | Journal of Nuclear Materials |
| Volume | 557 |
| DOIs | |
| State | Published - Dec 15 2021 |
Funding
Firstly, we thank the anonymous reviewers whose suggestions greatly improved the quality of the manuscript. We thank Dr. Ekkehard Post from Netzsch Inc. for H2O (g) atmosphere methodological support and testing. We also thank Mr. Cole Moczygemba for plotting final figure forms. The tested materials were based upon work supported by the US Department of Energy, Office of Nuclear Energy Advanced Gas Reactor Fuel Qualification and Development Program and Department of Energy Nuclear Energy University Programs, Award Number: DE-NE0008798. This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Firstly, we thank the anonymous reviewers whose suggestions greatly improved the quality of the manuscript. We thank Dr. Ekkehard Post from Netzsch Inc. for H 2 O (g) atmosphere methodological support and testing. We also thank Mr. Cole Moczygemba for plotting final figure forms. The tested materials were based upon work supported by the US Department of Energy, Office of Nuclear Energy Advanced Gas Reactor Fuel Qualification and Development Program and Department of Energy Nuclear Energy University Programs, Award Number: DE-NE0008798. This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Keywords
- Graphite matrix material
- High-temperature gas-cooled reactors
- High-temperature oxidation
- Matrix oxidation products
- Nuclear materials