NSUF 18-1130: Post-irradiation analysis at the nanoscale of 14YWT after high dose (16.6 dpa) neutron irradiation at 386C and 412C
The objective of this investigation is to perform detailed microstructural characterization at the nanoscale of neutron irradiated specimens of the oxide dispersion strengthened (ODS) 14YWT ferritic alloy (SM13 heat), with nominal composition Fe-14Cr-3W-0.4Ti-0.3Y2O3 (wt.%). The specimens of interest are TEM disks that have been neutron irradiated at the BOR-60 reactor, in Russia, to ~16.6 dpa at 386C and ~412C. The BOR-60 reactor is one of the only operating sodium fast experimental reactors in operation in the world, and 14YWT is a candidate material to be used as fuel cladding in fast reactors. The scarcity of neutron sources worldwide together with the difficulty to access and handle neutron irradiated samples put an added value to any results arising from this study, which will represent a benchmark in understanding the microstructural stability of this alloy under real reactor conditions. The aim of this proposal is to assess any potential microstructural changes induced by the neutron irradiation conditions: in the grain size and orientation relationships between grains, in the atomic structure and chemistry of the oxygen-enriched nanoclusters, in the distribution of solute atoms near grain boundaries or any changes in the composition profiles of grain boundaries. A variety of scanning transmission electron microscopy (S/TEM), scanning electron microscopy (SEM) transmission Kikuchi Diffraction (tKD) and atom probe tomography (APT) techniques will be used to achieve this goal, together with the use of the focused ion beam (FIB) lift-out technique for sample preparation. The results of this study will also provide the first opportunity to discover if Cr-rich alpha' precipitates may have formed in 14YWT during neutron irradiation. A significant amount of microstructural characterization has been performed on the 14YWT (SM13 heat) alloy in the unirradiated condition, which will greatly aid in making conclusions regarding neutron radiation microstructural effects on these samples. Furthermore, a benefit of this study will also be comparing the microstructural characterization results from neutron irradiation experiments with those from similar ion irradiation experiments. A detailed APT analysis of 14YWT (SM13 heat) ion irradiated at the Center for Accelerator Mass Spectrometry (CAMS) in Lawrence Livermore National Laboratory (LLNL), CA with Fe++ ions (70 MeV, 20 dpa) at 450C has already been completed under a DoE-NEUP IRP framework. The results arising from this proposal will definitely help to make a correlation between ion and neutron irradiation effects in materials. The desired time frame for conducting the specimen preparation, TEM, APT and SEM-tKD analysis may take no more than 6 months. The preparation of TEM and APT samples by the FIB lift-out technique in the LAMDA facility is estimated to take no more than 2 months, depending on the instrument availability. TEM and SEM-tKD experimental work in the LAMDA facility will be performed in parallel to APT characterization in Oxford during the following 2 months. Data analysis and reporting will be made during the last 2 months.
Additional Info
| Field | Value |
|---|---|
| Abstract | The objective of this investigation is to perform detailed microstructural characterization at the nanoscale of neutron irradiated specimens of the oxide dispersion strengthened (ODS) 14YWT ferritic alloy (SM13 heat), with nominal composition Fe-14Cr-3W-0.4Ti-0.3Y2O3 (wt.%). The specimens of interest are TEM disks that have been neutron irradiated at the BOR-60 reactor, in Russia, to ~16.6 dpa at 386C and ~412C. The BOR-60 reactor is one of the only operating sodium fast experimental reactors in operation in the world, and 14YWT is a candidate material to be used as fuel cladding in fast reactors. The scarcity of neutron sources worldwide together with the difficulty to access and handle neutron irradiated samples put an added value to any results arising from this study, which will represent a benchmark in understanding the microstructural stability of this alloy under real reactor conditions. The aim of this proposal is to assess any potential microstructural changes induced by the neutron irradiation conditions: in the grain size and orientation relationships between grains, in the atomic structure and chemistry of the oxygen-enriched nanoclusters, in the distribution of solute atoms near grain boundaries or any changes in the composition profiles of grain boundaries. A variety of scanning transmission electron microscopy (S/TEM), scanning electron microscopy (SEM) transmission Kikuchi Diffraction (tKD) and atom probe tomography (APT) techniques will be used to achieve this goal, together with the use of the focused ion beam (FIB) lift-out technique for sample preparation. The results of this study will also provide the first opportunity to discover if Cr-rich alpha' precipitates may have formed in 14YWT during neutron irradiation. A significant amount of microstructural characterization has been performed on the 14YWT (SM13 heat) alloy in the unirradiated condition, which will greatly aid in making conclusions regarding neutron radiation microstructural effects on these samples. Furthermore, a benefit of this study will also be comparing the microstructural characterization results from neutron irradiation experiments with those from similar ion irradiation experiments. A detailed APT analysis of 14YWT (SM13 heat) ion irradiated at the Center for Accelerator Mass Spectrometry (CAMS) in Lawrence Livermore National Laboratory (LLNL), CA with Fe++ ions (70 MeV, 20 dpa) at 450C has already been completed under a DoE-NEUP IRP framework. The results arising from this proposal will definitely help to make a correlation between ion and neutron irradiation effects in materials. The desired time frame for conducting the specimen preparation, TEM, APT and SEM-tKD analysis may take no more than 6 months. The preparation of TEM and APT samples by the FIB lift-out technique in the LAMDA facility is estimated to take no more than 2 months, depending on the instrument availability. TEM and SEM-tKD experimental work in the LAMDA facility will be performed in parallel to APT characterization in Oxford during the following 2 months. Data analysis and reporting will be made during the last 2 months. |
| Award Announced Date | 2018-02-01T14:09:54.243 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Kory Linton |
| Irradiation Facility | None |
| PI | Maria A Auger |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1130 |