NUKLEONIKA 2006, 51(Suppl. 2):s53-s57
Olga Stawarz1, Maria Karpińska2, Kalina Mamont-Ciesla1
1 Dosimetry Department, Central Laboratory for Radiological Protection,
7 Konwaliowa Str., 03-194 Warsaw, Poland
2 Department of Biophysics, Medical University of Białystok,
2A Mickiewicza Str., 15-089 Białystok, Poland
PicoRad system based on activated charcoal collectors and liquid scintillation counter is one of the
most popular passive methods of radon measurements which may be used both indoors and in other
environments such as caves, tunnels, mines etc. It is well known that charcoal is also a very good
adsorber of water vapor and it can reduce adsorption efficiency for radon. In PicoRad collectors,
the charcoal is mixed with a dessicant to lower this effect.
A series of expositions of PicoRad detectors was performed in a Central Laboratory for Radiological
Protection (CLOR) radon calibration/climatic chamber to study the effect of high relative humidity on
the airborne radon concentration measurements and the dependence of the results on the duration of
exposure. The results obtained from the PicoRad system were referred to the mean concentrations
delivered by an AlphaGUARD monitor, Genitron (GmbH), Germany. The main conclusions are the following:
1) the PicoRad system results are not affected by high relative humidity, including extreme values of 90-96%,
for the duration of exposure up to ca. 24 h;
2) in the relative humidity range of 75-96% the correction coefficient linearly depends on the duration
of exposure reaching a value of ca. 16 for 96 h exposure;
3) the PicoRad system delivers results corresponding better to the mean value of radon
concentration in the last 6 h interval of exposure than that in the whole exposure duration.
This finding is particularly important for the calibration of PicoRad collectors in the conditions
of decreasing radon concentration due to radon decay.