The article presents the results of a gamma- spectrometer study with a low- capacity scintillation (NaI(Tl)) detection unit, with software GammaVision v.8, adopted to solve certification problems, including for measuring activities close to zero. The list of factors influencing the presentation of the minimum detected activity (MDA) in the report protocol is analyzed software GammaVision v.8. To perform the measurements, the company´s ORTEC gamma-spectrometer with a low-capacity detection  unit a type digiBASE-RH, in which a high-voltage power supply unit, amplifier, digital multi-channel analyzer with USB-connection to a computer with the installed driver are installed, was used. The peak search in the library was performed using a compressed version of the library, which contains two nuclides 137Cs and 40K. Methods of calculating MDA are based on the intensity of accounts. Nuclide activity is calculation for all peaks in the library, the energy of which is in the selected energy ranges for analysis. Measurements and calculations MDA under the given conditions of research for five methods depending on time of measurement and geometry of measurements are carried out. It is shown that the level of MDA can be reduced by choosing the optimal conditions, time of measurement and geometry of measurements. Recommendations are given for the use of capacity for counting sample, which will reduce the amount of substance required for analysis and optimize the time spent on measuring the counting sample. In a prospect it is expedient to undertake a study of dependence of MDA from the physical properties and radionuclide composition of the substance for the counting sample and the dependence from the uncertainty in the equation MDA.

The article provides a systematic approach to quality control of measurements of total alpha-and beta-activity using a counter with a low background ALPHA / BETA COUNTING SYSTEM ALBA (mod. ALBA / LLAB) and software ALBA 2000 v.2.5.6. The purpose is to determine the compliance of these objects with the requirements of regulatory documentation. The spectrometry method is based on the physical concentration of radionuclides from the sample volume, measuring the rate of alpha, and beta radiation of the obtained dry residue of the sample, comparing the sample count rate with calibration values of activity, and calculating the total alpha, beta activity of the sample. The primary means of testing is a counter with a low background ALPHA / BETA COUNTING SYSTEM ALBA 200, the lower limit of measurements of the alpha activity, which is 0.02 Bq/l, and beta activity of 0.1 Bq/l, the relative random uncertainty of the measurement result is 60 % with a confidence level P = 0.95. The efficiency of registration on the alpha channel of 43 %, background on the alpha channel of 0,11 imp./min, for a measurement time of 60,000 s, the efficiency of registration on the beta channel of 30 %, background on the beta channel of 1,9 imp./min, for measurement time 60000 s. As a comparison sample for calculating total alpha activity, a sample with alpha radiation, 241Am (geometry 2π), is used. To calculate the total beta activity, a sample of beta-emitter of potassium sulfate with radionuclide is used at 40K (geometry 2π). The weight of the counting sample ranges from 200 to 1000 mg. The activity values are calculated automatically, using the software ALBA 2000, v.2.5.6. Measurement of the total activity of radionuclides in counting samples using the method should be performed only in calibrated geometries. At the same time, the safety requirements, personnel qualifications, and test conditions must be met. Quality control of measurements in the alpha, beta counter ALBA-2000 v.2.5.6. It is carried out in qualitative and quantitative ways.