Characteristics of commercially available CdZnTe detector as gamma-ray spectrometer under severe nuclear accident

Around sites of severe nuclear accidents such as the Fukushima Daiichi Nuclear Power Plant, in-situ measurements of gamma-ray energy spectra and identifying radionuclides are important for radiological protection from both external and internal dose uptake.For such applications, a commercially available CdZnTe spectrometer (Kromek GR-1) was characterized within the calibration fields at the Facility of Radiation Standards (FRS) of Japan Atomic Energy Agency (JAEA).The angular dependence of detection efficiency was studied using the photoelectric peak counts of the 137 Cs and 226 Ra gamma-rays.The efficiency was kept within 15 % degradation in the range from -135˚ to 135˚, which covers 85% of all incident angles, for gamma-rays above 242 keV.The usable dose ranges for peak-energy and energy spectrum measurements were investigated by evaluating the photoelectric peak channel and comparing the air kerma rates calculated from the measured gamma-ray spectra to the reference ones determined by the ionization chamber.The spectrometer could correctly measure the gamma-ray spectra and the photoelectric peak of the 137 Cs gamma-ray below 200 μGy•h -1 and 3 mGy•h -1 , respectively.