Study on Method for Simultaneous Determination of Ambient Dose Equivalent Rates and Activity Concentration in Air for Environmental Radiation Monitoring

Abstract

For proper environmental radiation monitoring, a method to simultaneously determine ambient dose equivalent rate and radioactivity concentration in the air by using a newly developed scintillation spectrometer, namely a CeBr 3 spectrometer was investigated. The performance of the proposed method, including energy dependence, angular dependence and the linearity of the spectrometer (i.e. the dose rate dependence of its re-sponse), was verified by a series of measurements, conducted according to the procedure of inter-comparison of detectors used for early warning network performed by the European Radiation Dosimetry Group (EURADOS). Measurement results show that the proposed method is suitable for environmental radiation monitoring pur-poses. After thorough tests, the investigation on obtaining activity concentration in air from the pulse height spectrum of γ-ray was demonstrated in the laboratory by using a point-like sealed 133 Ba source to simulate an artificial increase of ambient dose equivalent rate due to a radioactive cloud containing 131 I and 133 Xe. The photon fluence rate was obtained from the pulse height spectrum by using the unfolding method, and the activ ity concentration in air for radionuclides of interest could be estimated from the obtained photon fluence rate by applying the conversion coefficient evaluated via a Monte Carlo calculation.