RESUMO
Alpha-particle counting at a defined solid angle (DSA) is one of the most accurate methods used in the primary activity standardization of alpha-particle emitting radionuclides. The important features of the technique are geometrically calculated efficiency and low background energy spectra. This paper describes measurement conditions of the DSA counter installed at Turkish Atomic Energy Authority - Sarayköy Nuclear Research and Training Center (TAEK-SANAEM) and source preparation apparatus. Details of source preparation, preliminary work of measurement and solid angle calculations are explained. The standardization of the activity of 241Am sources with detailed uncertainty analysis is reported as part of a validation of the method.
RESUMO
A commercially available Fidelis ionization chamber was calibrated and assessed in PTB with activity standard solutions. The long-term stability and linearity of the system was checked. Energy-dependent efficiency curves for photons and beta particles were determined, using an iterative method in Excel™, to enable calibration factors to be calculated for radionuclides which were not used in the calibration. Relative deviations between experimental and calculated radionuclide efficiencies are of the order of 1% for most photon emitters and below 5% for pure beta emitters. The system will enable TAEK-SANAEM to provide traceable activity measurements.
RESUMO
Dissolution of radionuclides of interest is an indispensable first step in the alpha spectrometric analysis of soil samples. In this study a uranium recovery method for the analysis of uranium isotopes in soil samples is presented. Two different soil sample dissolution techniques were used: digestion in open beaker and fusion. The results of these techniques were compared. Two proficiency test samples and one reference material prepared by the IAEA were analyzed. Better results were obtained by fusion dissolution technique but impurities were higher than with acid leaching. Results of two techniques were more or less similar within the uncertainty limits. The detection limit (a(#)) was evaluated as part of the quality control.
RESUMO
Qualifications of uncertainties associated with the measurement of specific activity concentration of uranium radioisotope ((238)U) in water samples by alpha-particle spectrometry are presented. Possible sources of uncertainty are identified and quantified in the activity concentration measurements of (238)U isotope; the major source being the statistical counting uncertainty as expected. The combined relative standard uncertainty [Formula: see text] of the measurement was calculated as 1.4Bq kg(-1) (7.9%) for the investigated NPL sample. The accuracy and precision of recommended procedure were checked analysing six spiked water samples supplied from IAEA-proficiency test exercises. The results were evaluated in terms of relative bias, z-score, u-score, trueness and precision. These results show that the activity values and their uncertainties are in good agreement with recommended values.
RESUMO
An alpha spectrometric method for the rapid determination of 226Ra isotope in water samples is presented. The method is based on the co-precipitation of (Ba)(Ra)SO4 for source preparation. The parameters contributing to the uncertainty budget are investigated. Geometry factor (solid angle / 4pi) was used instead of 226Ra standard disc for the determination of detector efficiency. The analytical method has been successfully applied to the determination of 226Ra for water samples in proficiency tests organized by International Atomic Energy Agency (IAEA) and National Physical Laboratory (NPL). The proposed method also showed high reproducibility.
