Development and calibration of a real-time airborne radioactivity monitor using gamma-ray spectrometry on a particulate filter

In this work, we present the development and calibration of a real-time airborne radioactivity monitor (patent pending) to be used in an automatic environmental radiation surveillance network. The monitor collects a constant flow of air that passes across a particulate filter, where the airborne aerosols are collected. Then, the filter is faced to a NaI(Tl) or LaBr₃(Ce) scintillation detector that is used for gamma-ray spectrometry. This permits, in realtime, to identify and quantify the airborne radioactive isotopes. The monitor was fully calibrated combining experimental data and Monte Carlo simulations. For the simulations, a user code including a model of the system geometry was prepared for the EGS5 code system and validated with experimental measurements. The calibration methodology is independent of the scintillation crystal used; however, the measurement capabilities and the performance of the monitor are not. Thus, we finally discuss some characteristics of the monitor when using the different crystals.