Abstract
Sapphire (α-Al2O3) is a candidate fiber-optic sensor material for extreme temperature environments, potentially including those of nuclear reactors. However, its optical transmission under high-dose neutron irradiation is not well understood compared with that of conventional fused silica. This study examined dimensional changes, optical transmission, and irradiation-induced defects in neutron-irradiated α-Al2O3 at temperatures of 298 °C to 688 °C and doses of 3.2 to 12 dpa. Although previous studies attributed radiation-induced attenuation (RIA) at the highest irradiation temperatures to increased optical scattering from radiation-induced voids, our findings indicate that scattering from neither voids nor dislocation loops can explain the measured attenuation. Instead, absorption due to aluminum vacancy centers appears more likely based on a comparison of the spectral features of the measured optical attenuation with previous literature. Significant c-axis swelling (5.51 % ± 0.83 %) was observed in the 12 dpa, 592 °C irradiated sample, much higher than earlier measurements, suggesting temperature sensor drift of 543 °C to 1,140 °C. Void patterning was predominantly observed along the a-axis, differing from previous studies on polycrystalline samples, which showed c-axis patterning. Dislocation loops evolved into network dislocations with increasing temperature and dose; voids formed within these structures, showing no size or density changes, indicating an atypical growth mechanism.
| Original language | English |
|---|---|
| Article number | 155695 |
| Journal | Journal of Nuclear Materials |
| Volume | 607 |
| DOIs | |
| State | Published - Mar 2025 |
Funding
The characterization and analysis reported here were supported by the Advanced Sensors and Instrumentation program of the US Department of Energy's Office of Nuclear Energy (DOE-NE). The irradiation experiments were funded by the ORNL Laboratory Directed Research and Development Program, managed by UT- Battelle, LLC, for the US DOE. A portion of this research used the irradiation capabilities of HFIR, a DOE Office of Science User Facility operated by ORNL. The optical transmission measurements were funded by DOE-NE under DOE Idaho Operations Office Contract DE-AC07–051D14517 as part of a Nuclear Science User Facilities rapid turnaround experiment. We gratefully acknowledge the valuable insights from Dr. Steven J. Zinkle of the University of Tennessee, Knoxville. Tony Birri, Travis Dixon, and Kyle Everett (ORNL) assisted with the optical transmission measurements. The characterization and analysis reported here were supported by the Advanced Sensors and Instrumentation program of the US Department of Energy's Office of Nuclear Energy (DOE-NE). The irradiation experiments were funded by the ORNL Laboratory Directed Research and Development Program, managed by UT- Battelle, LLC, for the US DOE. A portion of this research used the irradiation capabilities of HFIR, a DOE Office of Science User Facility operated by ORNL. The optical transmission measurements were funded by DOE-NE under DOE Idaho Operations Office Contract DE-AC07-051D14517 as part of a Nuclear Science User Facilities rapid turnaround experiment. We gratefully acknowledge the valuable insights from Dr. Steven J. Zinkle of the University of Tennessee, Knoxville. Tony Birri, Travis Dixon, and Kyle Everett (ORNL) assisted with the optical transmission measurements.
Keywords
- Neutron irradiation
- Optical fibers
- Radiation-induced attenuation
- Sapphire
- Transmission electron microscopy
- Voids