Main results of the international intercomparison of passive radon detectors under field conditions in Marie Curie's tunnel in Lurisia (Italy)

In recent years a large number of radon intercomparison exercises has been organized; most of them took place in radon chambers, in reference atmosphere of the parameter to control (i.e. radon gas) under temperature, humidity and atmospheric pressure stable conditions. In 2014, in the tunnel belonging to the Lurisia spas complex (Lurisia, Piedmont, Italy), with natural high concentrations of uranium and radon gas, an intercomparison exercise has been held to give to radon measurement services and laboratories the possibility to test their passive systems under field conditions, which are less controlled and much more challenging. The response of laboratories was very positive: 46 participants from 10 European countries and 3 non-European countries. Generally about 80% of results of participants were considered acceptable even if it was observed a global trend of a substantial underestimation of the actual radon concentration

Metrological aspects of international intercomparison of passive radon detectors under field conditions in Marie Curie's tunnel in Lurisia

In 2014, an intercomparison exercise of passive radon detectors under field conditions in the Marie Curie's tunnel belonging to the Lurisia spas complex (Lurisia, Piedmont, Italy) has been held. Radon activity concentration in the tunnel was measured with six radon active monitors, previously calibrated at ENEA-INMRI facilities. In the present paper, a synthesis of the metrological aspects of the intercomparison is given. Indeed particular attention was paid to metrological characterization of radon monitors and their response upon ambient conditions. Correction factors have been defined to be applied when measurements are performed in severe environmental conditions. In particular, it has been found that monitors are particularly sensitive to the effect of air density: the AlphaGUARD (AG-SAPHYMO, GmbH) efficiency decreases with the air density, while for the MR1 PLUS (Tesys, Italy), the opposite applies. When the reference monitors were placed into the Marie Curie's tunnel, to the recorded average radon concentrations correction factors were applied. After the correction the difference between data coming from AG and MR1 PLUS is within the 1.7%