Intercomparison of dose rates obtained from scintillation detectors with different shape in the environmental monitoring, 2; Simulation

Tsuda, Shuichi  ; Yoshida, Tadayoshi ; Tanigaki, Minoru*; Okumura, Ryo*; Saito, Kimiaki  

Environmental dose rate monitoring has been performed using scintillation detectors since the Fukushima Dai-ichi Nuclear Power Plant accident happened. It is necessary to evaluate the influence of directional dependence on indicated values, because scintillation detectors with such dependence are used, though photons come from various direction in the environment. In this study, pulse height spectra were measured using scintillation detectors with different crystal configurations and ambient dose equivalent rates were obtained using spectrum - dose conversion operators. The ratio of dose rates calculated in a simulated environmental radiation field agrees with the measurement fairly well. The calculated dose rates of CsI(Tl) cylindrical crystals with varying height-to-diameter ratios indicated that the environmental dose rates can be estimated by a simple calibration using a unidirectional beam, provided that a crystal configuration and an irradiation surface are properly selected.