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Development of the fiber-optic sensor with a large surface area to measure radioactive contamination in soil at nuclear facility site

Once decommissioning of a nuclear facility is completed, it shall be confirmed if its site meets the site release criteria. For this the residual radioactivity in the site should be measured and assessed. This paper developed and characterized the fiber-optic sensor with a large surface area for measurement of radioactivity in soil at nuclear facility site, which is less time-consuming due to ease of measurement. The fiber-optic sensor consisted of a radiation sensing probe including scintillator panel and light guide and a transmission optical fiber. The light measuring system was assembled combining it with photomultiplier tube, pre-amplifier, multichannel analyser and display. Several measurements using the light measuring system showed that, as for measuring time for measurement of cesium-137 source, 1,800 sec was the optical measurement duration, and as for reflector, aluminium foil was the best.