Development of a Miniaturized and Embedded Optical Fiber Dosimeter for Drone Inspection

We present a new miniaturized architecture of a fiber-based dosimeter exploiting the radiation-induced attenuation (RIA) of a phosphosilicate single-mode optical fiber to monitor in real-time the total ionizing dose (TID) up to 70 Gy(SiO2) with a few mGy(SiO2) dose resolution. This system of less than 200 g with its packaging has been embedded on a foldable drone able to be deployed in high radiation zone (HRZ) at nuclear facilities through a one meter long, 100 mm diameter diagnostic hole allowing to access the HRZ through its biological wall. To achieve these performances, the operation principle of the dosimeter has been deeply optimized to improve the quality of a fiber coil RIA measurement around 1530 nm, in particular by considering the impact of light polarization in the dual channels sensing architecture. Its performances have been first assessed through60Co  -ray radiation testing up to 107 Gy(air). The opto- and micro-electronics components of the sensor show no degradation up to this maximal achieved TID. In this generation of dosimeter, which employs a 160 m coil of radiation-sensitive optical fiber, the measurable TID range is up to 70 Gy with 2 mGy dose resolution, corresponding to more than 50 dB of dynamic range. This latter can be adapted by varying the fiber length for monitoring other radiation environments. After its calibration, the dosimeter has been embedded on the drone and multiple short irradiation runs allowed to benchmark the dose measurements done by the embedded dosimeter to the ones provided by the137Cs -ray source facility at ORANO La Hague. Results agree within 5%, demonstrating the feasibility to perform embedded dosimetry during drone missions in HRZ.