Correction Techniques of Radiation Induced Errors for Raman Distributed Temperature Sensor and Experiment at the Experimental Fast Reactor: JOYO

Abstract

Optical fibers have advantages like flexible configuration, intrinsic immunity for electromagnetic fields etc., and they have been used as optical fiber sensors. By some of these techniques, continuous or discrete distribution of physical parameters can be measured. Here, in order to apply Raman distributed temperature sensor (RDTS) to the monitoring of nuclear facilities, some correction techniques for radiation induced errors were investigated. It has been shown that, when uniform loss distribution can be assumed, simple correction technique with two thermocouples can be applied. Moreover, if loop type arrangement is applied, even when the loss distribution is not uniform, radiation induced errors can be canceled.
For the demonstration of the feasibility of this technique, measurements using a commercial RDTS system were carried out along the primary piping system of the experimental fast reactor: JOYO. During the continuous measurements with the total dose of more than 10⁷R, the radiation induced errors showed a saturating tendency. The correction technique with two thermocouples was applied and its feasibility has been demonstrated. Although the time response of the system should be improved, the RDTS can be expected as a noble temperature monitor in nuclear facilities.