A method to overcome the saturation of real-time radon detectors used in high natural radiation regions

Saturation is a severe problem in high natural radiation exposure areas when the continuous instruments such as AlphaGAURD are used for real-time measurements of radon concentration in soil gas. In the case of radon measurements in Ramsar (a city located in northern Iran), high level of radon concentrations in the soil gas lead the detector to a saturation status. For this, we presented a practical method to handle this issue that is based on the control of radon concentration by dilution technique. First, in order to evaluate and verify our method, a measurement set-up using the 222Rn calibration source (PYLON RN1025) was established. The experimental results for the calibration testing of the measuring unit and the data for the performance of the method, confirm our procedure with good accuracy. In the second step, in field measurements using this method were performed in the selected locations of saturated radon concentration (36 locations), taking into account the meteorological parameters and seasonal effect. We have measured the radon concentration in the soil air with various dilution factors. We achieved a maximum radon concentration of 5480kBq⋅m−3 in the soil gas of the study area, Ramsar city, Iran, which is 2–3 times the upper detection limit of the detector. The obtained results ensure the use of active radon monitors for measuring high-level concentrations and can be used as a technique for radon mapping in high natural radiation exposure areas. The study explained here may represent a step forward in the practical approach of such measurements. [Display omitted] •A technique established to evaluate high radon concentration exceeding the upper detection limit of the AlphaGUARD.•Radon monitoring in regions of high radon levels with good accuracy.•Measurement of radon concentration in Ramsar city up to about 5480kBqm−3•Monitoring high level of natural activity with an active method.