The results of investigation of detector made of cadmium zinc telluride (CdZnTe or CZT) crystal with a working volume of 1500 mm 3 are presented. The detector is shown to have good spectrometric characteristics in registering gamma radiation from 241 Am, 57 Co, 137 Cs and 60 Co sources and can be effectively used for low-background measurements.

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The results of application of gamma-spectrometric technologies for carborne radiation survey in the NPP vicinity are presented [1-7]. The methods presented were developed at Nuclear Radiation Monitoring Laboratory, Moscow Engineering Physics Institute. The methods presented were developed at Nuclear Radiation Monitoring Laboratory, Moscow Engineering Physics Institute. The principal feature of the methods developed is that no prior information about any gamma-emitting source characteristics (radionuclide combination, etc.) and radiation background data are to be used for sources localization and identification. The methods can be applied when the car is moving and under conditions of strong spatial variations in the radiation background. The gamma-spectrometric methods developed are fundamentally ahead of the dosimetric ones in terms of sensitivity and information content. The special methods for gamma-spectrometric data processing and analyzing were developed and implemented in the SMS Na Avto software and SAS Na Avto software.

The feasibility of correct NaI gamma-spectrometry activity measurement for each nuclide in 131I, 132I, 133I, 134I, 135I, 133Xe, 135mXe, 135Xe and 222Rn composition is presented. To get this result the special matrix method M3 and SAS Na M3 software were used for spectra processing. SAS Na M3 software was developed for complex NaI gamma-spectra processing. Special algorithms and auxiliary software are used to overcome the problems of the classic spectra processing matrix method. Being used for spectrum processing SAS Na M3 software determines the nuclide composition of the sample, activity of nuclides identified and activities uncertainties. The activity values estimation is made for nuclides not identified in the sample measured but included in SAS Na M3 software nuclides library. The values of minimal detectable activities for NaI ∅3''× 3'' gamma-spectrometer and 1 hour measuring time are ~ 0.6 Bq for 131I, 132I, 133I, 134I and ~ 2 Bq for 135I.