Brillouin optical time-domain analysis (BOTDA) sensors offer remarkable advantages for the surveillance of the planned French deep geological radioactive wastes repository, called Cigéo<sup>1,2</sup>. In this work we study the performances of Brillouin distributed sensors in harsh environment. We evaluate the radiation tolerance of different sensor classes and their responses evolution during γ-ray exposition with 1kGy/h dose rate (to reach ~0.2MGy) and after 1, 3, 6 and 10 MGy accumulated doses. Measurements on strained Ge-doped SMF are reported to highlight the variation on Brillouin scattering proprieties, both intrinsic frequency position of Brillouin shift and its dependence on temperature and strain.
Raman Distributed Temperature Sensors (RDTS) offer exceptional advantages for the monitoring of the envisioned French deep geological repository for nuclear wastes, called Cigéo. Here, we present experimental studies on how the performances of RDTS evolve in harsh environments like those associated with H<sub>2</sub> or γ-rays. Both of them are shown to strongly affect the temperature measurements made with RDTS. We showed that by adapting the characteristics of the used fiber for the sensing, we could limit its degradation but that additional hardening by system studies will have to be developed before integration of RDTS in Cigéo.