Alpha particle counting system at SANAEM. Preliminary measurements as a part of validation studies.

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.

Standardization of 142Pr activity concentration.

142Pr (praseodymium-142), a potential radionuclide for brachytherapy, was produced after irradiating high purity natural Pr2O3 powder in a research reactor. The irradiated powder was then dissolved in acids and diluted for measurement. Several radioactivity measurement methods were used in the standardization of 142Pr radionuclide. This work reports the results of standardization of 142Pr with CIEMAT/NIST efficiency tracing method, gamma spectrometry and a calibrated ionization chamber. The activity measured from different standardization methods are compatible with each other within the uncertainty limits. The CIEMAT/NIST efficiency tracing method gives the lowest uncertainty and is a reliable method for the standardization of this radionuclide.

Calibration and efficiency curve of SANAEM ionization chamber for activity measurements.

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.