Kelly McCary

Optical fibers provide a variety of options for instrumentation in reactor environments. Multiple physical phenomena can be measured using optical fibers including, temperature, strain, pressure, and fluid level. Optical fibers are advantageous because they are immune to electromagnetic interference, have a small diameter (~125 µm), and have a fast response. This work investigates temperature sensing with sapphire optical fiber in the Ohio State University Research Reactor (OSURR). Specifically, this work investigates temperature sensing, using the Optical Frequency Domain Reflectometry (OFDR) sensing technique. A Luna Innovations Optical Backscatter Reflectometer (OBR) 4600, was used with sapphire optical fibers with an internal cladding and that were inscribed with type-II fiber Bragg gratings (FBGs). The sapphire fiber optic temperature sensors were irradiated in the central irradiation facility (CIF) of the OSURR for five days and received a total fluence of approximately 2.5x1018 n/cm2 and a gamma dose of approximately 3.48 Grad. The temperature was uncontrolled and the maximum temperature of the air in the CIF reached approximately 80 ºC, as measured by a k-type thermocouple. Further development and characterization of the cladding process will enable the deployment of nearsingle mode sapphire optical fiber as high temperature radiation resistant sensors.