NSUF 18-1392: TEM/EDS study of Nb redistribution in ZrNb alloys following proton irradiation
We propose to study the effect of irradiation on Nb redistribution in ZrNb alloy. The research objectives of this study are to provide knowledge on the Nb redistribution and quantify Nb concentration in both precipitates and matrix after irradiation. The overall research program aims at precisely characterizing the microstructure and microchemistry of proton irradiated ZrNb alloys, before and after corrosion, with different Nb contents, below and above the theoretical solid solubility limit to better understand in-reactor corrosion behavior of Zr-Nb alloys. This study will utilize Titan Themis 200 Transmission Electron Microscope (TEM/STEM) with Super-X Energy Dispersive Spectroscopy (EDS) at IMCL to study proton irradiated samples that have been already prepared by FIB liftout technique. The samples are Zr-xNb binary model alloys (x=0.2,0.5,1.0wt%) all irradiated up to 1 dpa at 350°C. STEM/EDS examinations will focus on characterizing the microstructure and microchemistry of the concentrated Nb phases (ßNb native precipitates and Nb rich irradiation-induced needle like precipitates). Atomic scale resolution STEM images of precipitates and their interface with matrix will be taken to determine crystal structure of precipitates and the orientation relationship with the matrix. In addition, ultra-high counting EDS mapping and line scan will provide precise Nb content data in both precipitates and matrix. Then, STEM/EDS data will be used to compare with the results from upcoming Atomic Probe Tomography (APT) experiments for validation. After corrosion experiments, same geometry FIB samples will be prepared, and same TEM/STEM/EDS technique will be used on Titan to examine the microstructure and microchemistry change after corrosion. Indeed, Nb solute concentration, known to control the fuel cladding corrosion kinetics, may be lowered by precipitation of radiation induced Nb rich needle like particles. However, it is still unclear if the Nb in these radiation induced precipitates come from native precipitates dissolution or from Nb originally in solid solution. This decrease of Nb in solid solution under irradiation is hypothesized to be primarily responsible for the relatively low in-reactor corrosion kinetics experienced by ZrNb alloys even at large burnups (up to 80 Gwd/MTU), at the contrary to Zircaloys which experience an increase in corrosion kinetics at relatively high burnup (~50 Gwd/MTU). This overall hypothesis is tested through an on-going research program at the PIs laboratory, and this RTE would bring critical data for its success. This information will allow for the contribution to and re-evaluation of current fuel cladding design in order to maximize safety and burnup for use in current generation of nuclear reactors. This RTE will also inform the on-going effort to evaluate the potential for proton irradiation to mimic neutron irradiation for fuel cladding licensing purposes.
Additional Info
| Field | Value |
|---|---|
| Abstract | We propose to study the effect of irradiation on Nb redistribution in ZrNb alloy. The research objectives of this study are to provide knowledge on the Nb redistribution and quantify Nb concentration in both precipitates and matrix after irradiation. The overall research program aims at precisely characterizing the microstructure and microchemistry of proton irradiated ZrNb alloys, before and after corrosion, with different Nb contents, below and above the theoretical solid solubility limit to better understand in-reactor corrosion behavior of Zr-Nb alloys. This study will utilize Titan Themis 200 Transmission Electron Microscope (TEM/STEM) with Super-X Energy Dispersive Spectroscopy (EDS) at IMCL to study proton irradiated samples that have been already prepared by FIB liftout technique. The samples are Zr-xNb binary model alloys (x=0.2,0.5,1.0wt%) all irradiated up to 1 dpa at 350°C. STEM/EDS examinations will focus on characterizing the microstructure and microchemistry of the concentrated Nb phases (ßNb native precipitates and Nb rich irradiation-induced needle like precipitates). Atomic scale resolution STEM images of precipitates and their interface with matrix will be taken to determine crystal structure of precipitates and the orientation relationship with the matrix. In addition, ultra-high counting EDS mapping and line scan will provide precise Nb content data in both precipitates and matrix. Then, STEM/EDS data will be used to compare with the results from upcoming Atomic Probe Tomography (APT) experiments for validation. After corrosion experiments, same geometry FIB samples will be prepared, and same TEM/STEM/EDS technique will be used on Titan to examine the microstructure and microchemistry change after corrosion. Indeed, Nb solute concentration, known to control the fuel cladding corrosion kinetics, may be lowered by precipitation of radiation induced Nb rich needle like particles. However, it is still unclear if the Nb in these radiation induced precipitates come from native precipitates dissolution or from Nb originally in solid solution. This decrease of Nb in solid solution under irradiation is hypothesized to be primarily responsible for the relatively low in-reactor corrosion kinetics experienced by ZrNb alloys even at large burnups (up to 80 Gwd/MTU), at the contrary to Zircaloys which experience an increase in corrosion kinetics at relatively high burnup (~50 Gwd/MTU). This overall hypothesis is tested through an on-going research program at the PIs laboratory, and this RTE would bring critical data for its success. This information will allow for the contribution to and re-evaluation of current fuel cladding design in order to maximize safety and burnup for use in current generation of nuclear reactors. This RTE will also inform the on-going effort to evaluate the potential for proton irradiation to mimic neutron irradiation for fuel cladding licensing purposes. |
| Award Announced Date | 2018-05-17T10:57:22.783 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Alina Zackrone |
| Irradiation Facility | None |
| PI | zefeng yu |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1392 |