An imaging plate (IP) was applied to measure tritium in high 60Co gamma-ray radiation fields. The IP made of europium-doped BaFBr(I), a photostimulated luminescence (PSL) material, is a two-dimensional radiation sensor. The PSL response of the IP has a peak at 20-50 keV and steeply decreases towards higher energy, falling by one hundredth at around 1 MeV. By utilizing a large difference in the PSL response to photon energy between 60Co (1.173 and 1.333 MeV) and tritium (maximum energy of 18.6 keV), the bremsstrahlung X-ray induced by tritium beta ray was detected in mixed radiation fields with tritium and 60Co, varying 60Co dose rate in the range 0.0013 to 9.22 μGy/min. It was found that the effect of 60Co irradiation to PSL value, obtained by irradiated with tritium of 12.5 MBq, was negligible by dose rate of 4.38 μGy/min and there was only 7.0% difference of PSL value, obtained by irradiated with tritium of 100 MBq, between dose rate of 0.0013 and 9.22 μGy/min. The IP tritium measurement method can be a promising candidate to measure tritium in high gammaray radiation fields.
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