Dependence of dose rate measurement in the environment on crystal configuration of scintillation detectors

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

Environmental dose rate monitoring has been performed using scintillation detectors since the Fukushima Dai-ichi Nuclear Power Plant accident happened. After the accident, various scintillation detectors with directional dependence are used in the measurement, though detectors with superior directional dependence are needed because photons come from various direction in the environment. To investigate the influence of crystal configurations on indicated values of dose rates, pulse height spectra were measured using scintillation-based detectors with different crystal configurations and ambient dose rates were obtained using a spectrum - dose conversion operator (G(E) function). It is found that the dose rate for a rectangular-parallelepiped crystal is 40% than that for a cylindrical one at the maximum. However, the values agreed within 10% among all the detectors irrespective of the crystal shapes, using G(E) functions determined in a rotational irradiation geometry.