Activity measurement of electron-capture radionuclides by a KX-gamma-coincidence method at VNIIM

The article describes the development of a KX-γ-coincidence method implemented in the prototype setup developed at the ionizing radiation department of the D.I. Mendeleyev Institute for Metrology. The first part was presented at Third European IRPA Congress (2010 June 14-18, Helsinki, Finland). NaI(Tl) crystals of 100 μm×40 mm and 80 mm×80 mm are used for photon radiation detection. A set of “ORTEC NIM” units and ADC “MKGB-01” are used for coincident pulse processing. The activity of electron-capture radionuclides 54Mn, 57Co, 65Zn, 85Sr, 88Y, 139Ce and 119mSn was measured. The expanded uncertainty (k=2) of activity was estimated in the range of 1-2%. The main metrological characteristics of the setup were determined: long-term stability, background, dead time, resolving time. The results obtained are in good agreement with international comparisons results and the Russian national standard of radioactivity.