Study on method for simultaneous determination of ambient dose equivalent rates and activity concentration in air for environmental radiation monitoring

Kowatari, Munehiko; Tanimura, Yoshihiko   ; Kessler, P.*; Neumaier, S.*; Rttger, A.*

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 spectrometer was investigated. The performance of the proposed method, including energy dependence and linearity of the spectrometer, 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 monitoring purposes. After thorough tests, the activity concentration in air was determined in the laboratory by using a point-like sealed Ba source to mimic a radioactive cloud containing I and Xe. The photon fluence rate was obtained from the pulse height distribution by using the unfolding method, and the activity concentration in air for radioisotopes of interest, mainly Xe, was estimated from the obtained photon fluence rate by applying the conversion coefficient evaluated via a Monte Carlo calculation. The results additionally show that the method presented in this study is reliable and suitable for the environmental radiation measurement.