NSUF 16-766: Fission Gas Bubble Characterizations of High-Energy Xe Implanted U3Si2
Gaseous fission products such as Xe and Kr form bubbles within nuclear fuel materials during operation. The fission gas bubbles compromise the fuel performance by causing gaseous swelling, degrading thermal conductivity, and eventually initiating fission gas release and fuel cracking. Fission gas behavior is therefore an important factor determining fuel performance. Fission gas bubbles form within grains (intragranular) as well as on grain boundaries (intergranular). The evolution mechanisms and influence on bulk properties differs between intragranular and intergranular bubbles. Thus, quantitative information such as the size distribution and number density of both types of bubbles is crucial to predicting the degradation of bulk fuel properties by these microstructural modifications. Because fission gas behavior is simultaneously driven by thermally-activated Xe diffusion and radiation-enhanced Xe diffusion, fuel temperature also plays an important role in controlling the size distribution and number density of various types of fission gas bubbles. As a result, previous experimental data focusing on low-temperature research reactor conditions are not sufficient for the establishment of advanced fuel performance codes to evaluate U3Si2 as an accident tolerant fuel (ATF) in LWRs. While in-pile neutron irradiation tests (ATF-1 campaign) and corresponding post-irradiation examination (PIE) microstructure characterization results will not be available till 2018, ion irradiation testing can work as an inexpensive alternative to study radiation effects in U3Si2. In particular, for nuclear fuel materials, when high-energy (~100 MeV level) fission product ions are used, the actual energetic fission products (which cause the majority of the radiation-induced microstructural modifications in real nuclear fuels) can be replicated using a powerful accelerator. Hence, this proposed project aims to take advantage of the efficiency and economy of high-energy ion irradiation to produce valuable experimental references for the ongoing development of advanced fuel performance models to evaluate U3Si2 as an ATF in LWRs. Thus, the fission gas behavior models can be preliminarily optimized. Further fine optimization will be done one in-pile irradiation data produced by ATF-1 campaign are available. Accordingly, three sintered U3Si2 samples irradiated by 84 MeV Xe ions to 1.03×1017 ions/cm-2 at 300°C, 450°C, and 600°C, respectively, will be investigated along with an as-received (control) sample. The irradiation temperatures cover the typical U3Si2 fuel temperatures at LWR conditions, whereas the irradiation dose provides a peak Xe concentration equivalent to 5% burnup. A TEM foil and a 20 µm × 20 µm × 20 µm cube will be prepared from each sample using FIB. The TEM foils will be investigated to establish the morphology, size distribution, and number density of Xe bubbles at different irradiation temperatures. Additionally, through a separate non-NSUF proposal, the FIB cubes will be investigated using multiple synchrotron scattering techniques. The investigations will include high energy diffraction microscopy (HEDM) as well as wide-angle and small-angle X-ray Scattering (WAXS & SAXS) to reveal the development of lattice strain, potential phase decomposition/amorphization, and quantitative characteristics of small Xe bubbles. The results of this proposed project will help facilitate multiple modeling efforts supported by the NEAMS-ATF HIP program by providing experimental data at LWR conditions for model optimization, parameterization, and validation. FIB sample preparation will take six (6) days, with half the time spent preparing TEM samples and half preparing synchrotron cubes; TEM examination will take four (4) days, 1 day for each TEM sample. The total time required is within the RTE proposal limitation.
Additional Info
| Field | Value |
|---|---|
| Abstract | Gaseous fission products such as Xe and Kr form bubbles within nuclear fuel materials during operation. The fission gas bubbles compromise the fuel performance by causing gaseous swelling, degrading thermal conductivity, and eventually initiating fission gas release and fuel cracking. Fission gas behavior is therefore an important factor determining fuel performance. Fission gas bubbles form within grains (intragranular) as well as on grain boundaries (intergranular). The evolution mechanisms and influence on bulk properties differs between intragranular and intergranular bubbles. Thus, quantitative information such as the size distribution and number density of both types of bubbles is crucial to predicting the degradation of bulk fuel properties by these microstructural modifications. Because fission gas behavior is simultaneously driven by thermally-activated Xe diffusion and radiation-enhanced Xe diffusion, fuel temperature also plays an important role in controlling the size distribution and number density of various types of fission gas bubbles. As a result, previous experimental data focusing on low-temperature research reactor conditions are not sufficient for the establishment of advanced fuel performance codes to evaluate U3Si2 as an accident tolerant fuel (ATF) in LWRs. While in-pile neutron irradiation tests (ATF-1 campaign) and corresponding post-irradiation examination (PIE) microstructure characterization results will not be available till 2018, ion irradiation testing can work as an inexpensive alternative to study radiation effects in U3Si2. In particular, for nuclear fuel materials, when high-energy (~100 MeV level) fission product ions are used, the actual energetic fission products (which cause the majority of the radiation-induced microstructural modifications in real nuclear fuels) can be replicated using a powerful accelerator. Hence, this proposed project aims to take advantage of the efficiency and economy of high-energy ion irradiation to produce valuable experimental references for the ongoing development of advanced fuel performance models to evaluate U3Si2 as an ATF in LWRs. Thus, the fission gas behavior models can be preliminarily optimized. Further fine optimization will be done one in-pile irradiation data produced by ATF-1 campaign are available. Accordingly, three sintered U3Si2 samples irradiated by 84 MeV Xe ions to 1.03×1017 ions/cm-2 at 300°C, 450°C, and 600°C, respectively, will be investigated along with an as-received (control) sample. The irradiation temperatures cover the typical U3Si2 fuel temperatures at LWR conditions, whereas the irradiation dose provides a peak Xe concentration equivalent to 5% burnup. A TEM foil and a 20 µm × 20 µm × 20 µm cube will be prepared from each sample using FIB. The TEM foils will be investigated to establish the morphology, size distribution, and number density of Xe bubbles at different irradiation temperatures. Additionally, through a separate non-NSUF proposal, the FIB cubes will be investigated using multiple synchrotron scattering techniques. The investigations will include high energy diffraction microscopy (HEDM) as well as wide-angle and small-angle X-ray Scattering (WAXS & SAXS) to reveal the development of lattice strain, potential phase decomposition/amorphization, and quantitative characteristics of small Xe bubbles. The results of this proposed project will help facilitate multiple modeling efforts supported by the NEAMS-ATF HIP program by providing experimental data at LWR conditions for model optimization, parameterization, and validation. FIB sample preparation will take six (6) days, with half the time spent preparing TEM samples and half preparing synchrotron cubes; TEM examination will take four (4) days, 1 day for each TEM sample. The total time required is within the RTE proposal limitation. |
| Award Announced Date | 2016-12-16T07:44:26.653 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Yaqiao Wu |
| Irradiation Facility | None |
| PI | Yinbin Miao |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 766 |