NSUF 18-1424: Active Irradiation Testing of Temperature Sensing Capability of Clad Sapphire Optical Fibers with Type 2 Bragg Gratings using Optical Backscatter Reflectometry

We propose active irradiation testing of the temperature sensing capability of clad sapphire optical fibers with Type 2 Fiber Bragg Gratings (FBGs) in the Ohio State University Research Reactor (OSURR) using an Optical Backscatter Reflectometer (OBR). Our motivation is that in-pile sensing is important for the qualification of advanced nuclear fuels and materials. Moreover, advanced high temperature reactors will require novel instrumentation for process control and on-line condition monitoring. Optical fiber-based sensors are promising candidates for in-pile sensing due to their small diameter (~100 µm) and the fact that they are fabricated from high temperature-tolerant, radiation-hard materials. Furthermore, spatially distributed temperature and/or strain measurements are possible with sub-cm resolution. Distributed temperature measurements made by the PI and co-PI using Type 2 fiber Bragg gratings (FBGs) inscribed in single-mode fused silica (a-SiO2) optical fibers survived three days of irradiation in the central irradiation facility (CIF) of the OSURR, with no observable signal degradation. However, the operating temperatures of silica fiber-based sensors are generally limited to less than 900°C. Fuel centerline temperatures can easily exceed 1,000°C for ceramic fuels and even for some metallic fuels. For these extremely high temperature applications, single crystal sapphire (a-Al2O3) optical fiber-based sensors are much better suited, as sapphire fibers have shown thermal stability up to 1,600°C. The primary challenges to making distributed measurements using sapphire fibers are (1) creating a grating in the sapphire fiber that will survive extreme temperatures and intense irradiation, and (2) achieving an effective cladding for the sapphire fibers that allows single-mode light transmission. To address these challenges, the co-PI has patented a unique process for establishing a cladding around the surface of sapphire fibers inscribed with the same radiation-tolerant Type 2 FBGs used in silica fibers. The sapphire fibers with cladding and gratings are currently available and ready for irradiation testing.

This work proposes 5 days of irradiation in the CIF of the OSURR using a simple rig that is identical to ones used in previous tests performed by the PI. The total project duration is 9 months. While no efforts will be made to vary the irradiation temperature, gamma heating in the facility results in temperatures typically in the range of 200-300°C. In-situ distributed temperature measurements will be made during irradiation using a Luna Innovations OBR, provided by the co-PI. In addition to monitoring signal degradation, the in-pile measurements will be compared with measurements from a Type K thermocouple to check for signs of signal drift. This sensor irradiation testing will be complemented by out-of-pile furnace testing (up to 1,600°C) to determine thermal stability outside of the scope of this rapid turnaround experiment. If these separate effects tests are successful, the results will set the stage for combined high temperature irradiation testing in the OSURR, followed by higher dose sensor testing led by the PI.

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필드	값
Abstract	We propose active irradiation testing of the temperature sensing capability of clad sapphire optical fibers with Type 2 Fiber Bragg Gratings (FBGs) in the Ohio State University Research Reactor (OSURR) using an Optical Backscatter Reflectometer (OBR). Our motivation is that in-pile sensing is important for the qualification of advanced nuclear fuels and materials. Moreover, advanced high temperature reactors will require novel instrumentation for process control and on-line condition monitoring. Optical fiber-based sensors are promising candidates for in-pile sensing due to their small diameter (~100 µm) and the fact that they are fabricated from high temperature-tolerant, radiation-hard materials. Furthermore, spatially distributed temperature and/or strain measurements are possible with sub-cm resolution. Distributed temperature measurements made by the PI and co-PI using Type 2 fiber Bragg gratings (FBGs) inscribed in single-mode fused silica (a-SiO2) optical fibers survived three days of irradiation in the central irradiation facility (CIF) of the OSURR, with no observable signal degradation. However, the operating temperatures of silica fiber-based sensors are generally limited to less than 900°C. Fuel centerline temperatures can easily exceed 1,000°C for ceramic fuels and even for some metallic fuels. For these extremely high temperature applications, single crystal sapphire (a-Al2O3) optical fiber-based sensors are much better suited, as sapphire fibers have shown thermal stability up to 1,600°C. The primary challenges to making distributed measurements using sapphire fibers are (1) creating a grating in the sapphire fiber that will survive extreme temperatures and intense irradiation, and (2) achieving an effective cladding for the sapphire fibers that allows single-mode light transmission. To address these challenges, the co-PI has patented a unique process for establishing a cladding around the surface of sapphire fibers inscribed with the same radiation-tolerant Type 2 FBGs used in silica fibers. The sapphire fibers with cladding and gratings are currently available and ready for irradiation testing. This work proposes 5 days of irradiation in the CIF of the OSURR using a simple rig that is identical to ones used in previous tests performed by the PI. The total project duration is 9 months. While no efforts will be made to vary the irradiation temperature, gamma heating in the facility results in temperatures typically in the range of 200-300°C. In-situ distributed temperature measurements will be made during irradiation using a Luna Innovations OBR, provided by the co-PI. In addition to monitoring signal degradation, the in-pile measurements will be compared with measurements from a Type K thermocouple to check for signs of signal drift. This sensor irradiation testing will be complemented by out-of-pile furnace testing (up to 1,600°C) to determine thermal stability outside of the scope of this rapid turnaround experiment. If these separate effects tests are successful, the results will set the stage for combined high temperature irradiation testing in the OSURR, followed by higher dose sensor testing led by the PI.
Award Announced Date	2018-05-17T11:04:50.91
Awarded Institution	None
Facility	None
Facility Tech Lead	Raymond Cao
Irradiation Facility	None
PI	Christian Petrie
PI Email	[email protected]
Project Type	RTE
RTE Number	1424