Temperature Resistant Fiber Bragg Gratings for On-Line and Structural Health Monitoring of the Next-Generation of Nuclear Reactors.

The harsh environment associated with the next generation of nuclear reactors is a great challenge facing all new sensing technologies to be deployed for on-line monitoring purposes and for the implantation of SHM methods. Sensors able to resist sustained periods at very high temperatures continuously as is the case within sodium-cooled fast reactors require specific developments and evaluations. Among the diversity of optical fiber sensing technologies, temperature resistant fiber Bragg gratings are increasingly being considered for the instrumentation of future nuclear power plants, especially for components exposed to high temperature and high radiation levels.

State-of-strain evaluation with fiber Bragg grating rosettes: application to discrimination between strain and temperature effects in fiber sensors.

An optical rosette that incorporates fiber Bragg gratings as strain gauges has been designed, fabricated, and tested. We investigated it by measuring the state of strain of a thin plate as the test structure submitted to an increasing load in a four-point bending configuration and for various angular orientations. This device has also been successfully investigated as a self-temperature-compensated in situ uniaxial strain sensor without any angular dependence and with high accuracy in recovery analysis, leading us to expect many industrial applications.