NSUF 13-419: Toward an understanding of the effect of dose rate on the irradiation response of F-M alloys
Ferritic-martensitic (F-M) alloys are leading candidates for cladding and structural components in fusion and advanced fission reactors, due to their high strength, resistance to thermal stresses, dimensional stability, and low activation. Throughout their service lifetime, these materials will be exposed to neutron irradiation doses as high as several hundred displacements per atom (dpa). Ions are commonly used to simulate the neutron damage at these high doses, due to their higher damage rates and minimal residual radioactivity, allowing for quicker and more cost-effective experiments. However, an increased irradiation dose rate increases the rate of point defect recombination, and thus, the temperature or final dose of the irradiation may need to be varied in order to achieve comparable microstructures or microchemistries. Understanding these dose rate effects is key to using ion irradiation techniques to assess the long-term viability of F-M alloys in advanced reactor systems. Limited studies have been carried out on neutron-irradiated F-M materials, so the dose rate effect has yet to be resolved for F-M alloys. Furthermore, irradiation effects are highly sensitive to variations between heats of the same alloy, and thus far, there are no published studies that have examined neutron and ion irradiation on the same heat of an F-M alloy. This project aims to significantly advance the understanding of dose rate effects in F-M alloys, and will thereby fill the aforementioned gap in the literature, by providing a comparison between neutron and ion irradiation damage on the same heats of alloys. In the proposed work, the microstructure, phase stability, and radiation-induced segregation (RIS) will be characterized in three commercial F-M alloys – T91, HCM12A, and HT9 – which have been irradiated in the Advanced Test Reactor (dose rate ~10-7 dpa/sec) to 3 dpa at a minimum temperature of 500°C. These samples originated from the same heats of alloys as have already been studied under proton irradiation (~10-5 dpa/sec) and self-ion irradiation (~10-3 dpa/sec) by the principal investigator and colleagues at the PI’s previous institution of employment. Data collected under this proposal will be compared with results from the proton and self-ion irradiated specimens, for which extensive microstructure, precipitate, and RIS analyses have already been carried out. This proposal presents a rare and unique opportunity to compare irradiation effects in F-M alloys over three dose rates, in the same alloy heats. A combination of transmission electron microscopy (TEM) and local electrode atom probe (LEAP) analyses will provide a thorough characterization of the irradiated microstructure, phases, and grain boundary RIS. This proposal requests access to the Microscopy and Characterization Suite (MaCS) at the Center for Advanced Energy Studies (CAES), for 6 days on the FEI Quanta focused ion beam, 4 days on the CAMECA 4000X HR LEAP, and 6 days on the FEI Tecnai TEM.
Additional Info
| Field | Value |
|---|---|
| Abstract | Ferritic-martensitic (F-M) alloys are leading candidates for cladding and structural components in fusion and advanced fission reactors, due to their high strength, resistance to thermal stresses, dimensional stability, and low activation. Throughout their service lifetime, these materials will be exposed to neutron irradiation doses as high as several hundred displacements per atom (dpa). Ions are commonly used to simulate the neutron damage at these high doses, due to their higher damage rates and minimal residual radioactivity, allowing for quicker and more cost-effective experiments. However, an increased irradiation dose rate increases the rate of point defect recombination, and thus, the temperature or final dose of the irradiation may need to be varied in order to achieve comparable microstructures or microchemistries. Understanding these dose rate effects is key to using ion irradiation techniques to assess the long-term viability of F-M alloys in advanced reactor systems. Limited studies have been carried out on neutron-irradiated F-M materials, so the dose rate effect has yet to be resolved for F-M alloys. Furthermore, irradiation effects are highly sensitive to variations between heats of the same alloy, and thus far, there are no published studies that have examined neutron and ion irradiation on the same heat of an F-M alloy. This project aims to significantly advance the understanding of dose rate effects in F-M alloys, and will thereby fill the aforementioned gap in the literature, by providing a comparison between neutron and ion irradiation damage on the same heats of alloys. In the proposed work, the microstructure, phase stability, and radiation-induced segregation (RIS) will be characterized in three commercial F-M alloys – T91, HCM12A, and HT9 – which have been irradiated in the Advanced Test Reactor (dose rate ~10-7 dpa/sec) to 3 dpa at a minimum temperature of 500°C. These samples originated from the same heats of alloys as have already been studied under proton irradiation (~10-5 dpa/sec) and self-ion irradiation (~10-3 dpa/sec) by the principal investigator and colleagues at the PI’s previous institution of employment. Data collected under this proposal will be compared with results from the proton and self-ion irradiated specimens, for which extensive microstructure, precipitate, and RIS analyses have already been carried out. This proposal presents a rare and unique opportunity to compare irradiation effects in F-M alloys over three dose rates, in the same alloy heats. A combination of transmission electron microscopy (TEM) and local electrode atom probe (LEAP) analyses will provide a thorough characterization of the irradiated microstructure, phases, and grain boundary RIS. This proposal requests access to the Microscopy and Characterization Suite (MaCS) at the Center for Advanced Energy Studies (CAES), for 6 days on the FEI Quanta focused ion beam, 4 days on the CAMECA 4000X HR LEAP, and 6 days on the FEI Tecnai TEM. |
| Award Announced Date | 2013-06-13T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Yaqiao Wu |
| Irradiation Facility | None |
| PI | Janelle Wharry |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 419 |