NSUF 13-388: X-ray characterization of fission gas bubble pressure in ion irradiated metallic alloy fuels
The formation and growth of fission gas bubbles in irradiated nuclear fuels is a process of vital technical importance because the behaviors of these gas bubbles have significant impact on the swelling of the fuel, which may lead to fuel failure during in-pile irradiation. This issue has been subject to extensive theoretical (simulations) and experimental investigations. One key question that remains to be answered, however, is the internal gas pressure of the fission gas bubbles in irradiated nuclear fuels. It has been shown in our ongoing research that the growth of fission gas bubbles in fuel materials is very sensitive to the internal pressure of the gas bubbles. In order to reduce the uncertainties that current meso-scale simulation techniques (kinetic rate theory or phase field approaches) for modeling nuclear fuel microstructural behaviors suffer from, experimental evaluations of key parameters such as gas bubble equation of state are imminent needs which clearly require knowledge of gas bubble pressure. The most reliable way to acquire such knowledge is through experimental investigations. With the unique capabilities of the Advanced Photon Source facility at Argonne National Laboratory, accurate estimate of internal gas bubble pressure becomes possible. X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) techniques will be employed in this proposed work to characterize Xe ion irradiated depleted U-Mo and depleted U-Zr alloy specimens. By working at low enough temperatures, X-ray absorption spectroscopy (XAS) results could be used to estimate Xe-Xe distances and coordination numbers. From a comparison with the cell parameter for fcc Xe (0.613nm at 5K), one could determine the xenon pressure within the gas bubbles (xenon aggregates). A method has also been established based on poro-elasticity theory to extrapolate the estimated internal gas pressure at low temperature (as measured) to the temperature at which the bubbles form during irradiations. Some research results have already demonstrated the similarity between ion and neutron irradiation generated defect structures in both cladding and structural materials and nuclear fuels. In particular, applying this method in nuclear fuel investigations make a stronger argument as a big fraction of damage in fuels are induced by heavy fission fragment instead of neutrons. Moreover, use of Xe irradiation has been demonstrated to produce similar gas bubble microstructures as reactor irradiated fuels with UO2. The specimens to be characterized include irradiated U-Mo and U-Zr materials that receive relatively low and high irradiation doses. The estimated internal gas pressure will help clarify the mechanisms by which fission gas bubbles grow as the sink efficiency of gas bubbles depends mainly on their internal gas pressures. The estimated gas bubble internal pressure values will also provide key guidance for kinetic rate theory and phase field simulations of metallic fuels by reducing the uncertainty in one of the critical parameters. To avoid unnecessary complications with sample oxidation after the ion irradiation experiments, we would like to have our experiments done in the early spring and we propose one week beam time for the experiment at the MRCAT beamline.
Additional Info
| Field | Value |
|---|---|
| Abstract | The formation and growth of fission gas bubbles in irradiated nuclear fuels is a process of vital technical importance because the behaviors of these gas bubbles have significant impact on the swelling of the fuel, which may lead to fuel failure during in-pile irradiation. This issue has been subject to extensive theoretical (simulations) and experimental investigations. One key question that remains to be answered, however, is the internal gas pressure of the fission gas bubbles in irradiated nuclear fuels. It has been shown in our ongoing research that the growth of fission gas bubbles in fuel materials is very sensitive to the internal pressure of the gas bubbles. In order to reduce the uncertainties that current meso-scale simulation techniques (kinetic rate theory or phase field approaches) for modeling nuclear fuel microstructural behaviors suffer from, experimental evaluations of key parameters such as gas bubble equation of state are imminent needs which clearly require knowledge of gas bubble pressure. The most reliable way to acquire such knowledge is through experimental investigations. With the unique capabilities of the Advanced Photon Source facility at Argonne National Laboratory, accurate estimate of internal gas bubble pressure becomes possible. X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) techniques will be employed in this proposed work to characterize Xe ion irradiated depleted U-Mo and depleted U-Zr alloy specimens. By working at low enough temperatures, X-ray absorption spectroscopy (XAS) results could be used to estimate Xe-Xe distances and coordination numbers. From a comparison with the cell parameter for fcc Xe (0.613nm at 5K), one could determine the xenon pressure within the gas bubbles (xenon aggregates). A method has also been established based on poro-elasticity theory to extrapolate the estimated internal gas pressure at low temperature (as measured) to the temperature at which the bubbles form during irradiations. Some research results have already demonstrated the similarity between ion and neutron irradiation generated defect structures in both cladding and structural materials and nuclear fuels. In particular, applying this method in nuclear fuel investigations make a stronger argument as a big fraction of damage in fuels are induced by heavy fission fragment instead of neutrons. Moreover, use of Xe irradiation has been demonstrated to produce similar gas bubble microstructures as reactor irradiated fuels with UO2. The specimens to be characterized include irradiated U-Mo and U-Zr materials that receive relatively low and high irradiation doses. The estimated internal gas pressure will help clarify the mechanisms by which fission gas bubbles grow as the sink efficiency of gas bubbles depends mainly on their internal gas pressures. The estimated gas bubble internal pressure values will also provide key guidance for kinetic rate theory and phase field simulations of metallic fuels by reducing the uncertainty in one of the critical parameters. To avoid unnecessary complications with sample oxidation after the ion irradiation experiments, we would like to have our experiments done in the early spring and we propose one week beam time for the experiment at the MRCAT beamline. |
| Award Announced Date | 2012-12-04T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Jeff Terry |
| Irradiation Facility | None |
| PI | Di Yun |
| PI Email | [email protected] |
| Project Type | APS |
| RTE Number | 388 |