Feasibility of optical sensing for robotics in highly radioactive environments

The application of robotics for repair, refurbishing, or dismantling of nuclear installations implies severe radiation resistance requirements. This is particularly critical when optical sensing is considered. The results of a series of γ irradiation experiments on such devices are reported and their behavior under radiation is identified. Test results show that carefully selected optical fibers can keep their radiation induced attenuation lower than 0.3 dB/m even up to a total dose of 10 MGy. Temperature annealing can even lower this attenuation down to 0.1 dB/m. Commercially available light emitting diodes and photodiodes present attenuations figures up to 15 dB, even after a gamma irradiation as low as 250 kGy. Properly chosen bias procedures are shown to greatly enhance this figure. The feasibility of optical sensing for proximity measurement and data transmission for nuclear robots used under severe radiation conditions is shown