Development of fiber optic hydrogen sensors for testing nuclear waste repositories

Fiber sensors are promising systems for monitoring hydrogen concentrations in the range 0-4% near the high radioactive wastes deposited in the underground laboratories of HADES (SCK-CEN Mol Research Centre in Belgium). We present the results, comparison and discussion of three different developments of hydrogen sensors developed: semitransparent palladium films, long length singlemode optical fiber without any preparation and fiber Bragg grating (FBG) coated with palladium.