NSUF 18-1545: Microstructural characterization of grain boundaries in Hastelloy N corroded in molten FLiBe salt under neutron irradiation
The Fluoride salt-cooled High-temperature Reactor (FHR) is being actively considered as the next generation nuclear reactor because it offers, among other benefits, a high degree of passive safety and high thermal efficiency. Integrating the successful experience of the Molten Salt Reactor Experiment (MSRE) program at the Oak Ridge National Laboratory (ORNL) with current advanced nuclear technologies, the primary coolant in the FHR will most likely be 7Li enriched FLiBe (2LiF-BeF2) salt. In support of the materials development for FHR, the in-reactor corrosion tests of candidate alloys, nickel-based Hastelloy N® in molten FLiBe were successfully conducted in nuclear research reactor at the Massachusetts Institute of Technology for 1000 hours. Our preliminary post-irradiation examinations (PIE) including visual observation and weight change indicate significant difference in the corrosion rate of in-reactor tested samples. In addition, some microstructure analyses including XRD, SEM, STEM have been carried out using the instruments at INL-CAES supported by NSUF (16-633). We observed Mo-rich precipitates with various geometries in grain boundaries. Mo is highly resistant to molten fluoride salt. The formation of these precipitates during in-core corrosion might significantly changes alloy corrosion behavior in molten salt in long term. However, the formation mechanism of grain boundary precipitate and its relationship to crucible material is not well understood. Therefore, we propose to characterize the microstructure of the grain boundaries of the Hastelloy N irradiated in molten salt (FLiBe) in graphite crucible and in nickel-lined crucible using the (1) SEM, EDS, FIB, and EBSD microscope system at IMCL, 5 days in total, to lift out lamellas and to identify grain boundary angle, (2) the Titan Themis 200 S/TEM with super-X EDS system, 5 days in total, to analyze precipitate chemistry and crystal structure.
Additional Info
| Field | Value |
|---|---|
| Abstract | The Fluoride salt-cooled High-temperature Reactor (FHR) is being actively considered as the next generation nuclear reactor because it offers, among other benefits, a high degree of passive safety and high thermal efficiency. Integrating the successful experience of the Molten Salt Reactor Experiment (MSRE) program at the Oak Ridge National Laboratory (ORNL) with current advanced nuclear technologies, the primary coolant in the FHR will most likely be 7Li enriched FLiBe (2LiF-BeF2) salt. In support of the materials development for FHR, the in-reactor corrosion tests of candidate alloys, nickel-based Hastelloy N® in molten FLiBe were successfully conducted in nuclear research reactor at the Massachusetts Institute of Technology for 1000 hours. Our preliminary post-irradiation examinations (PIE) including visual observation and weight change indicate significant difference in the corrosion rate of in-reactor tested samples. In addition, some microstructure analyses including XRD, SEM, STEM have been carried out using the instruments at INL-CAES supported by NSUF (16-633). We observed Mo-rich precipitates with various geometries in grain boundaries. Mo is highly resistant to molten fluoride salt. The formation of these precipitates during in-core corrosion might significantly changes alloy corrosion behavior in molten salt in long term. However, the formation mechanism of grain boundary precipitate and its relationship to crucible material is not well understood. Therefore, we propose to characterize the microstructure of the grain boundaries of the Hastelloy N irradiated in molten salt (FLiBe) in graphite crucible and in nickel-lined crucible using the (1) SEM, EDS, FIB, and EBSD microscope system at IMCL, 5 days in total, to lift out lamellas and to identify grain boundary angle, (2) the Titan Themis 200 S/TEM with super-X EDS system, 5 days in total, to analyze precipitate chemistry and crystal structure. |
| Award Announced Date | 2018-09-17T12:03:35.193 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Alina Zackrone |
| Irradiation Facility | None |
| PI | David Carpenter |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1545 |