| NUKLEONIKA 2010, 55(2):143-148
GAMMA-RAY SPECTROMETRY LABORATORY FOR HIGH-PRECISION MEASUREMENTS OF RADIONUCLIDE CONCENTRATIONS IN ENVIRONMENTAL SAMPLESPaweł Jodłowski, Stefan J. Kalita AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, 30 Mickiewicza Ave., 30-059 Kraków, Poland The paper outlines the methodology used in the Gamma-Ray Spectrometry Laboratory for high-precision measurements of radionuclide activity concentrations in environmental samples. The Laboratory equipment includes a semiconductor detector HPGe with a 42% relative efficiency. The detector is placed in a Pb housing made of bricks 10 cm in thickness. Three measurement geometries are considered: Marinelli beakers 710 cm3 in volume and two cylindrical geometries 121 and 48 cm3 in volume. In the efficiency calibration (E = 32÷1836 keV) mixed gamma standard solutions were used. Obtained experimental efficiency values ? were fitted with two quadratic functions. The junction point is that equivalent to 200 keV. Uncertainty of the calibration curve is 2% for E > 200 keV. The relationship between the total efficiency and the energy ?t(E) was also found for energies E = 33÷1250 keV. Self-absorption correction factors Cs are calculated by the method proposed by K. Debertin, the uncertainty level being 1÷2% for E > 100 keV. These correction factors are calculated by an original computer program. Coincidence summing correction factors Cc for the selected nuclides are derived using the ETNA computer program, basing on the relationships ?(E) and ?t(E). Minimum detectable activity (MDA) for selected nuclides encountered in environmental samples was determined for the water matrix. The methodology used was successfully verified in the course of international intercomparison measurements. Close X |