NSUF 15-600: Microstructure Characterization of High-Energy-Xe-Ion-Irradiated U-Mo
The dispersion-type fuel developed to be used in research and test reactors for reducing uranium enrichment is composed of U-Mo alloy fuel particles in a matrix of pure Al or an Al alloy, designated as U-Mo/Al. The design of qualified U-Mo/Al dispersion fuel relies heavily on the profound understanding of the radiation stability of the U-Mo-Al interaction product behavior and the gas-filled pore formation mechanism [1, 2]. To simulate fission fragment damage an irradiation study with 100MeV Xe ions was conducted on U-Mo fuel coated with Al. The experiment was designed to obtain qualitative and quantitative assessments of the microstructural evolution of the interaction products as a function of dose and damage rate, as well as assessing the development of large pores during irradiation. This study also aims to understand the fundamental mechanisms leading to Al penetration of diffusion barriers (ZrN or Si) to react with U-Mo, as has been observed in the high-flux regions of in-pile tests [3]. It is suspected that Al penetrates the diffusion barrier by diffusion in local thermal-spikes and mixing in global thermal-spikes [4] above a threshold fission rate. This experiment will allow determination of the Al penetration mechanism. Additionally, in U-Mo fuels irradiated in reactors, a fission-gas-bubble superlattice was observed that had a face centered cubic structure coherent with the host U-Mo body-centered cubic structure [5]. This microstructure is believed to be the most effective configuration to accommodate the insoluble gaseous fission products. Although important, an understanding of the formation mechanisms of the gas bubble superlattice are still missing. In this study, a high energy (100 MeV) Xe ion irradiation experiment is carried out on U-Mo fuels, aiming to understand the fundamental mechanisms leading to gas-bubble superlattice (three-dimensional ordering) formation and collapse. Eventually, these experiments may provide the possibility of designed material property modification by ion-matter interaction. The 100 MeV Xe ion irradiation experiment was performed at the ATLAS accelerator at Argonne National Laboratory. The characterization experiments will be carried out using Transmission Electronic Microscopy (TEM), Scanning Electronic Microscopy (SEM) and synchrotron irradiation techniques. Principal features of the irradiated microstructure are dislocations and bubbles/voids, which will be characterized using TEM. The structural and elemental information of the specimens will be obtained with SEM and TEM equipped with Energy Dispersive Spectroscopy (EDX). The approach of using SEM and TEM combined with FIB to characterize nuclear fuels has been successfully demonstrated in ref. [6]. In order to create a correlation between damage rate and the irradiated microstructure, it is critical to use Focused Ion Beam (FIB) milling to produce site-specific TEM samples over the full span of the ion damage profile (~ 7 µm in U-Mo).
Additional Info
| Field | Value |
|---|---|
| Abstract | The dispersion-type fuel developed to be used in research and test reactors for reducing uranium enrichment is composed of U-Mo alloy fuel particles in a matrix of pure Al or an Al alloy, designated as U-Mo/Al. The design of qualified U-Mo/Al dispersion fuel relies heavily on the profound understanding of the radiation stability of the U-Mo-Al interaction product behavior and the gas-filled pore formation mechanism [1, 2]. To simulate fission fragment damage an irradiation study with 100MeV Xe ions was conducted on U-Mo fuel coated with Al. The experiment was designed to obtain qualitative and quantitative assessments of the microstructural evolution of the interaction products as a function of dose and damage rate, as well as assessing the development of large pores during irradiation. This study also aims to understand the fundamental mechanisms leading to Al penetration of diffusion barriers (ZrN or Si) to react with U-Mo, as has been observed in the high-flux regions of in-pile tests [3]. It is suspected that Al penetrates the diffusion barrier by diffusion in local thermal-spikes and mixing in global thermal-spikes [4] above a threshold fission rate. This experiment will allow determination of the Al penetration mechanism. Additionally, in U-Mo fuels irradiated in reactors, a fission-gas-bubble superlattice was observed that had a face centered cubic structure coherent with the host U-Mo body-centered cubic structure [5]. This microstructure is believed to be the most effective configuration to accommodate the insoluble gaseous fission products. Although important, an understanding of the formation mechanisms of the gas bubble superlattice are still missing. In this study, a high energy (100 MeV) Xe ion irradiation experiment is carried out on U-Mo fuels, aiming to understand the fundamental mechanisms leading to gas-bubble superlattice (three-dimensional ordering) formation and collapse. Eventually, these experiments may provide the possibility of designed material property modification by ion-matter interaction. The 100 MeV Xe ion irradiation experiment was performed at the ATLAS accelerator at Argonne National Laboratory. The characterization experiments will be carried out using Transmission Electronic Microscopy (TEM), Scanning Electronic Microscopy (SEM) and synchrotron irradiation techniques. Principal features of the irradiated microstructure are dislocations and bubbles/voids, which will be characterized using TEM. The structural and elemental information of the specimens will be obtained with SEM and TEM equipped with Energy Dispersive Spectroscopy (EDX). The approach of using SEM and TEM combined with FIB to characterize nuclear fuels has been successfully demonstrated in ref. [6]. In order to create a correlation between damage rate and the irradiated microstructure, it is critical to use Focused Ion Beam (FIB) milling to produce site-specific TEM samples over the full span of the ion damage profile (~ 7 µm in U-Mo). |
| Award Announced Date | 2015-08-10T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Yaqiao Wu |
| Irradiation Facility | None |
| PI | Bei Ye |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 600 |