Priprema radioaktivnih standarda za kalibraciju gama spektrometara

Rutinska merenja uzoraka iz životne sredine gama spektrometrijom zahtevaju pripremu radioaktivnih standarda različitih matriksa. Radioaktivni standardi se koriste u svim fazama procesa merenja, uključujući validaciju metoda, kalibraciju i kontrolu kvaliteta. U Laboratoriji za Zaštitu od zračenja i zaštitu životne sredine, Instituta za nuklearne nauke „Vinča” radioaktivni standardi se pripremaju korišćenjem sertifikovanog radioaktivnog rastvora različitih radionuklida. U ovom radu je opisan postupak pripreme radioaktivnih standarda koji obuhvata izbor matriksa, pripremu i spajkovanje pripremljenih matriksa sa sertifikovanim radioaktivnim rastvorom, proveru homogenosti, pakovanje standarda u odgovarajuću geometriju i njihova merenja u kontakt geometriji na gama spektrometru. Za sve materijale matriksa pripremljeni su i uzorci „blenka“ i mereni u istoj geometriji kao i kalibracioni standardi. Nakon analize snimljenih spektara, fitovanjem datih tačaka efikasnosti dobijene su kalibracione krive. U ovom radu dat je i opis budžeta merne nesigurnosti za aktivnosti radionuklida prisutnih u pripremljenim standardima.
The routine measurements of environmental samples using gamma-ray spectrometry indicate the needs for preparing radioactive standards for various matrices. The radioactive standards are used in all phases of the measurement process, including method validation, calibration and quality control. In the Radiation and Environmental Protection Departmen in the "Vinča" Institute of Nuclear Sciences, radioactive standards are prepared using a certified radioactive solution of mixed radionuclides. The procedure for radioactive standards preparation, which includes matrix selection and preparation, spiking with a certified radioactive solution, homogeneity check, matrix packing in the appropriate geometry and measurement of the prepared standards using a gamma spectrometer, is described in this paper. For all matrix materials, "blank" samples were prepared in the same manner as the standard materials and measured in the same geometry as the calibration samples. After the analysis of recorded spectra and evaluation of the obtained data for efficiency at given energies, calibration curves were obtained by fitting. The uncertainty budget of the activity for all radionuclides present in the prepared standards is also defined in this paper.