b'Nuclear Science User Facilities Active Irradiation Testing of Temperature SensingCapability of Clad Sapphire Optical Fibers With Type 2Bragg Gratings Using Optical Backscatter ReflectometryChristian M. PetrieOak Ridge National Laboratory petriecm@ornl.govT his work investigatedcontrolled, but the thermocouples the temperature-sensingwere used to provide a reference to capabilities of Type II fiberwhich the fiber-based temperature Bragg gratings (FBGs) inscribed inmeasurements could be compared.sapphire optical fiber in The OhioResultsState University Research ReactorThe FBGs located closest to the (OSURR) (Figure 1). A Lunasilica-to-sapphire fiber splices Innovations 4600 optical backscattergenerally performed much better reflectometer (OBR) was used tothan the FBGs located further from interrogate FBGs in three sapphirethe splice. All measurements for optical fibers with an internalFBGs located more than ~510 cm cladding that was developed byfrom the silica-to-sapphire splice Ohio State [1]. The sapphire fiberseither failed or showed prohibitive were fusion-spliced to silica leadnoise, perhaps indicating that the fibers. In addition to the sapphirecladding of the sapphire fiber was fibers, two silica fibers with thenot effective in achieving single-same Type II FBGs were included inmode operation. However, for two the experiment as a reference. Theof the three sapphire fibers, the fiber-based sensors were irradiatedFBG located closest to the silica-to-in the Central Irradiation Facilitysapphire splice performed well, with (CIF) of the OSURR for a total ofthe magnitude and time response 40 hours over five days at a reactorof the fiber-optic measurements power of 450 kW, resulting in a totalgenerally matching those of the neutron fluence of approximatelythermocouples for all five days of 2.51018 n/cm2 and a gammairradiation (Figure 2). Some of the dose of approximately 3.48 Grad.observed differences between the Two K-type thermocouples werevarious sapphire fibers could be included within the rig: one at theattributed to pre-irradiation heat core centerline and the other 12treatment. The two sapphire fibers inches above the top of the core.that showed better performance The temperature was not activelywere heat treated at 1300C prior 68'