Development of simulated air filters for gamma-ray spectrometry proficiency testing

A set of 60 spiked simulated air filter sources was developed for the 2004-2005 proficiency test of the Italian radioactivity surveillance network. Each simulated filter source was prepared by reproducible volumetric dispensing of 19 drops of a mixed radioactive solution containing Co-57, Cs-134, Cs-137, Co-60 and Eu-152. The spiking pattern was investigated and optimized by numerical simulations. The filter sources were checked by double counting on HPGe and NaI(Tl) detectors. The standard deviation (SD) of activity values was 1.5%.