Development of a new passive integral dosemeter for gamma ray monitoring using an imaging plate

A new passive integral dosemeter for gamma ray monitoring is being developed using an imaging plate (IP). In the application of IPs to dosimetry, a fading effect causes serious problems. The fading is considered to be caused by the recombination or holes and charges trapped shallowly in the F centres, which have several activation energies. Appropriate annealing procedures allow elimination of trapped charges with low activation energies, and quantitative estimation of the radiation dose is possible. The optimum condition for minimising the effect of fading on dose estimation was obtained by post-irradiation annealing of BAS-MS (BAS-MS2025, fabricated by Fuji Film Co. Ltd) IPs at 80 degrees C for 24 h. This was confirmed by calculation. Under this condition, the detection limit was calculated to be 3.15 microSv when 10% error is allowed. A 1-month integral dose was measured by the IP. The results were compared with those obtained using a commercially available fluoro-glass dosemeter.