High temperature sensing using raman-DTS with single-crystal fibers for nuclear application

Results of high-temperature sensing with distributed single-crystal fiber based on a Raman optical-time-domainreflectometry (ROTDR) for nuclear applications is presented. A novel distributed temperature sensing (DTS) system for use with sapphire and YAG fibers was developed to monitor temperature in continuous radiation and high-temperature environments such as nuclear reactor cores or coolant loops. Performance evaluations including accuracy and repeatability of the DTS system are discussed in this paper. Calibration techniques have been implemented to correct the dynamic variation of the optical loss with temperature in the single-crystal fibers. In various sections of different types of fibers and under different temperatures, correction algorithms were used to calculate the calibration parameters to obtain an accurate temperature profile that allows deployment the sensing system under extreme conditions. Continuous calibration and sequential temperature measurement data were analyzed. Distributed temperature measurements with the single-crystal fibers under high radiation loads at high-temperatures have been carried out.