NSUF 17-952: Atom Probe Tomography Study of Neutron Irradiated U-Mo Fuel
U–7-10 wt% Mo based fuel has been developed for application in high performance research reactors. Fission gas bubbles are generated during irradiation of fuels and their characteristics and properties are an important factor that influences irradiation behavior of fuels. A three-dimensional highly-ordered gas bubble structure coherent with the host U–Mo bcc lattice. Despite the studies by TEM, the chemical compositions of the fission gas bubbles and the matrix, the number density and volume fraction of the fission gas bubbles, and the possible relations between the fission gas bubbles and solid fission products remain unclear. In addition, TEM provides two-dimensional information, and results on gas bubble superlattice obtained from TEM need to be verified by a three-dimensional technique. Atom probe tomography (APT) is an emergent characterization technique that is capable of determining the chemical identity of each individual atom and generating three-dimensional chemical maps imaging the distribution of individual atoms. APT offers three-dimensional information with simultaneously high spatial resolution and high analytical sensitivity. In the work previously performed using RERTR program funding, the first APT investigation of neutron irradiated U-Mo fuel was conducted. Fission gas bubble superlattice were observed in various orientations. However, APT was performed on U-Mo fuel at one fission density, and the APT experiment was conducted in laser mode, which may have caused heating to the tip samples and accordingly affect the accuracy of gas bubble composition measurements. Hence, more detailed APT studies in voltage mode are needed. The proposed study aims to obtain, through APT, distribution, composition, number density and volume fraction of fission products including fission gas bubbles and solid fission products in neutron irradiated U-Mo fuel. Such information obtained is anticipated to significantly advance the understanding of the irradiation behavior of U-Mo fuel. This project will use neutron irradiated U-10 wt% Mo dispersion fuel. APT tips and TEM lamellae will be taken, using focused ion beam (FIB), from inside the grain interiors and also across grain boundaries where large intergranular gas bubbles are absent. Most APT experiments will be performed in voltage mode, and a few measurement will be conducted in laser mode to ascertain the influence of possible heating in laser mode on accuracy of gas bubble measurement. Low sample/stage temperature (20 K) will be used for most APT experiments, and higher temperatures (e.g., 50 K) will be applied for a few experiments to investigate the possible effect of sample/stage temperature on APT measurements. The chemical composition, number density and volume fraction of fission gas bubbles and the chemical composition of the U-Mo matrix will be measured. The distribution and composition of solid fission products and their relations to fission gas bubbles will be obtained. The expected period of performance of the project is Apr. – Jun. 2017.
Additional Info
| Field | Value |
|---|---|
| Abstract | U–7-10 wt% Mo based fuel has been developed for application in high performance research reactors. Fission gas bubbles are generated during irradiation of fuels and their characteristics and properties are an important factor that influences irradiation behavior of fuels. A three-dimensional highly-ordered gas bubble structure coherent with the host U–Mo bcc lattice. Despite the studies by TEM, the chemical compositions of the fission gas bubbles and the matrix, the number density and volume fraction of the fission gas bubbles, and the possible relations between the fission gas bubbles and solid fission products remain unclear. In addition, TEM provides two-dimensional information, and results on gas bubble superlattice obtained from TEM need to be verified by a three-dimensional technique. Atom probe tomography (APT) is an emergent characterization technique that is capable of determining the chemical identity of each individual atom and generating three-dimensional chemical maps imaging the distribution of individual atoms. APT offers three-dimensional information with simultaneously high spatial resolution and high analytical sensitivity. In the work previously performed using RERTR program funding, the first APT investigation of neutron irradiated U-Mo fuel was conducted. Fission gas bubble superlattice were observed in various orientations. However, APT was performed on U-Mo fuel at one fission density, and the APT experiment was conducted in laser mode, which may have caused heating to the tip samples and accordingly affect the accuracy of gas bubble composition measurements. Hence, more detailed APT studies in voltage mode are needed. The proposed study aims to obtain, through APT, distribution, composition, number density and volume fraction of fission products including fission gas bubbles and solid fission products in neutron irradiated U-Mo fuel. Such information obtained is anticipated to significantly advance the understanding of the irradiation behavior of U-Mo fuel. This project will use neutron irradiated U-10 wt% Mo dispersion fuel. APT tips and TEM lamellae will be taken, using focused ion beam (FIB), from inside the grain interiors and also across grain boundaries where large intergranular gas bubbles are absent. Most APT experiments will be performed in voltage mode, and a few measurement will be conducted in laser mode to ascertain the influence of possible heating in laser mode on accuracy of gas bubble measurement. Low sample/stage temperature (20 K) will be used for most APT experiments, and higher temperatures (e.g., 50 K) will be applied for a few experiments to investigate the possible effect of sample/stage temperature on APT measurements. The chemical composition, number density and volume fraction of fission gas bubbles and the chemical composition of the U-Mo matrix will be measured. The distribution and composition of solid fission products and their relations to fission gas bubbles will be obtained. The expected period of performance of the project is Apr. – Jun. 2017. |
| Award Announced Date | 2017-04-26T10:08:27.17 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Alina Zackrone, Yaqiao Wu |
| Irradiation Facility | None |
| PI | Haiming Wen |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 952 |