Primary standardization of 153 Sm radioactive solution

The procedure followed by the Laboratorio de Metrologia Nuclear (LMN) at the IPEN, in Sao Paulo, for the standardisation of 153 Sm is described. This radionuclide is part of the LMN programme for the standardisation of important radionuclides used in nuclear medicine. The activity measurement was carried out in a 4π (PC)β-γ coincidence system consisting of a proportional counter, coupled to a pair of 3x 3NaI(Tl) crystals. This radionuclide was obtained by means of the 153 Sm (n,γ) 153 Sm reaction in a thermal neutron flux at the IPEN 2 MW research reactor. The solution activity was determined by the extrapolation technique, using external absorbers over and under the 153 Sm sources. The events were registered using a Time to Amplitude Converter associated with a Multichannel Analyser. (author)