NSUF 19-1774: Effect of Irradiation on Nuclear Graphite Microstructure in Relation to Oxidation in Oxygen Environments
One primary safety concern in Very High Temperature Reactors (VHTRs) is graphite oxidation during an air-ingress accident. The graphite oxidation rate is significantly affected by the mass transfer rate of relevant chemical species to the active oxidation sites from a flow stream, and the kinetic chemical reaction parameters. Research has been performed over the past decades to study the kinetic reaction behaviors of some of the latest developed nuclear graphite candidates, such as IG-110, NBG, and PECA. However, we still have very limited understanding of the effect of irradiation on the graphite oxidation. Neutron irradiation tends to close the graphite pores, thus slows down the mass transfer of the oxidant molecules and subsequently oxidation. On the other hand, neutron irradiation also breaks graphite crystal structures, which increases the quantity of active sites available for chemical reaction. Competing effects of these two mechanisms remain to be understood in the community. Therefore, we propose to investigate the effect of irradiation on graphite micro structure in relation to oxidation behaviors in oxygen environment.
This proposed project is divided into three phases. In Phase I, three nuclear grade graphite samples will be irradiated in the Michigan Ion Beam Laboratory (MIBL) by 10 MeV carbon ions to accumulate 5 dpa damages at high temperature, as they would encounter in a prototypic VHTR, within a depth about 7 µm from the surfaces. We are seeking NSUF to cover the irradiation fees through this call. Sample pieces will be then prepared from the irradiated graphite for structural characterization to study and correlate the effect of irradiation on graphite pore evolution. Sample will be analyzed by TEM and SEM. In addition, the specific surface area will be measured by a non-destructive examination method, such as high-resolution 3D X-ray tomography and Brunauer–Emmett–Teller (BET) technique. In Phase II, the mass transfer rate of oxidant molecules in the three irradiated samples will be measured using a Wicke-Kallenbach diffusion cell. Finally, the oxidation rate of the irradiated samples will be carefully measured using an existing oxidation apparatus at the leading university. In this proposed technical approach, each phase will use the data generated from the previous phases. Furthermore, pristine samples will be analyzed to provide a reference for comparison. The irradiated samples and characterization will be performed over a period of six weeks and the following analysis will be conducted over twelve weeks. The results of this proposed research will unveil the effect of irradiation on the graphite oxidation in oxygen environments, and serve as a benchmark for HTGR fuel development.
Допълнителна информация
| Поле | Стойност |
|---|---|
| Abstract | One primary safety concern in Very High Temperature Reactors (VHTRs) is graphite oxidation during an air-ingress accident. The graphite oxidation rate is significantly affected by the mass transfer rate of relevant chemical species to the active oxidation sites from a flow stream, and the kinetic chemical reaction parameters. Research has been performed over the past decades to study the kinetic reaction behaviors of some of the latest developed nuclear graphite candidates, such as IG-110, NBG, and PECA. However, we still have very limited understanding of the effect of irradiation on the graphite oxidation. Neutron irradiation tends to close the graphite pores, thus slows down the mass transfer of the oxidant molecules and subsequently oxidation. On the other hand, neutron irradiation also breaks graphite crystal structures, which increases the quantity of active sites available for chemical reaction. Competing effects of these two mechanisms remain to be understood in the community. Therefore, we propose to investigate the effect of irradiation on graphite micro structure in relation to oxidation behaviors in oxygen environment. This proposed project is divided into three phases. In Phase I, three nuclear grade graphite samples will be irradiated in the Michigan Ion Beam Laboratory (MIBL) by 10 MeV carbon ions to accumulate 5 dpa damages at high temperature, as they would encounter in a prototypic VHTR, within a depth about 7 µm from the surfaces. We are seeking NSUF to cover the irradiation fees through this call. Sample pieces will be then prepared from the irradiated graphite for structural characterization to study and correlate the effect of irradiation on graphite pore evolution. Sample will be analyzed by TEM and SEM. In addition, the specific surface area will be measured by a non-destructive examination method, such as high-resolution 3D X-ray tomography and Brunauer–Emmett–Teller (BET) technique. In Phase II, the mass transfer rate of oxidant molecules in the three irradiated samples will be measured using a Wicke-Kallenbach diffusion cell. Finally, the oxidation rate of the irradiated samples will be carefully measured using an existing oxidation apparatus at the leading university. In this proposed technical approach, each phase will use the data generated from the previous phases. Furthermore, pristine samples will be analyzed to provide a reference for comparison. The irradiated samples and characterization will be performed over a period of six weeks and the following analysis will be conducted over twelve weeks. The results of this proposed research will unveil the effect of irradiation on the graphite oxidation in oxygen environments, and serve as a benchmark for HTGR fuel development. |
| Award Announced Date | 2019-05-14T16:26:11.473 |
| Awarded Institution | Center for Advanced Energy Studies |
| Facility | Microscopy and Characterization Suite |
| Facility Tech Lead | Alina Zackrone, Kevin Field, Yaqiao Wu |
| Irradiation Facility | None |
| PI | Miao Song |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1774 |