On-line monitoring of environmental conditions in nuclear facilities is becoming a more and more important problem.
Standard electronic sensors are not the ideal solution due to radiation sensitivity and difficulties in installation of
multiple sensors. In contrast, radiation-hard optical fibres can sustain very high radiation doses and also naturally offer
multi-point or distributed monitoring of external perturbations. Multiple local electro-mechanical sensors can be replaced
by just one measuring fibre.
At present, there are over four hundred operational nuclear power plants (NPPs) in the world 1. Operating experience has
shown that ineffective control of the ageing degradation of major NPP components can threaten plant safety and also
plant life. Among those elements, cables are vital components of I&C systems in NPPs. To ensure their safe operation
and predict remaining life, environmental monitoring is necessary. In particular, temperature and radiation dose are
considered to be the two most important parameters.
The aim of this paper is to assess experimentally the feasibility of optical fibre temperature measurements in a low doserate
radiation environment, using a commercially available reflectometer based on Rayleigh backscattering. Four
different fibres were installed in the Sub-Pile Room of the BR2 Material testing nuclear reactor in Mol, Belgium. This
place is man-accessible during the reactor shut-down, allowing easy fibre installation. When the reactor operates, the
dose-rates in the room are in a range 0.005-5 Gy/h with temperatures of 40-60 °C, depending on the location. Such a
surrounding is not much different to some "hot" environments in NPPs, where I&C cables are located.