France’s State of the Art Distributed Optical Fibre Sensors Qualified for the Monitoring of the French Underground Repository for High Level and Intermediate Level Long Lived Radioactive Wastes

Abstract

This paper presents the state of the art distributed sensing systems, based on optical fibres, developed and qualified for the French Cigéo project, the underground repository for high level and intermediate level long-lived radioactive wastes. Four main parameters, namely strain, temperature, radiation and hydrogen concentration are currently investigated by optical fibre sensors, as well as the tolerances of selected technologies to the unique constraints of the Cigéo’s severe environment. Using fluorine-doped silica optical fibre surrounded by a carbon layer and polyimide coating, it is possible to exploit its Raman, Brillouin and Rayleigh scattering signatures to achieve the distributed sensing of the temperature and the strain inside the repository cells of radioactive wastes. Regarding the dose measurement, promising solutions are proposed based on Radiation Induced Attenuation (RIA) responses of sensitive fibres such as the P-doped ones. While for hydrogen measurements, the potential of specialty optical fibres with Pd particles embedded in their silica matrix is currently studied for this gas monitoring through its impact on the fibre Brillouin signature evolution.

Extreme Radiation Sensitivity of Ultra-Low Loss Pure-Silica-Core Optical Fibers at Low Dose Levels and Infrared Wavelengths

“…Interestingly, the F-doped and PSC fibers have also been identified as the most promising waveguides for data transfer or multi-parameter (temperature, strain, pressure, liquid level…) point or distributed sensing [ 3 ] in severe environments. Usually, these applications also work at telecom wavelengths to benefit from the technologies developed for telecommunications.…”

Near‐IR Radiation‐Induced Attenuation of Aluminosilicate Optical Fibers

“…Radiation effects on optical fibers have been intensively studied since more than 40 years, as the unique advantages of these waveguides are exploited for a large variety of applications (data transfer, diagnostics, discrete, or distributed sensors) in radiation‐rich environments associated with space, dismantling, nuclear waste repositories, and fusion‐ or fission‐related facilities. [ 1–4 ] Most of the past efforts focused on the identification of the most tolerant fiber compositions against the observed fiber darkening (radiation‐induced attenuation [RIA]) to build radiation tolerant or radiation‐hardened data links or sensors. [ 5–7 ] However, today, it is well known that some of the fiber compositions render the glass very sensitive to radiations, allowing its use as a radiation detector [ 8,9 ] or even as a dosimeter when this high sensitivity is combined with no RIA dependence on the other irradiation parameters: dose rate and temperature.…”

CYTOP Fibre Bragg Grating Sensors for Harsh Radiation Environments

“…Within the context of MODERN-2020, a project focusing on nuclear waste repositories, analyses indicate that solely gamma radiation is present in these storage cells. A good example of ongoing work includes that of Lesoille et al [1], who discussed quasi-distributed measurements for dosimetry, hydrogen, and temperature monitoring within a demonstrator of this application context.…”