New experimental device for a continuous soil gas radon variations monitoring

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Froٍka, Aleڑ; Mouèka, Ladislav; Rovenskل, Kateّina
Holding Date 11 October 2008

In order to monitor soil gas radon variations in the close vicinity of buildings, a new continuous detection system was developed and applied. The detection principle of the monitoring device is based on an airflow ionization chamber operating in a current mode. In addition, the unique sampling technical arrangements were designed and the take-off probe special end fitting, providing the defined continuous close circuit sampling, was applied.
The special sampling procedure effectively eliminates the ambient atmosphere influence on a long-term soil-gas sampling (temperature and pressure fields effects). The close circuit arrangement with defined flow characteristics ensures a minimal impact on physical properties of a sampling space (draining effects, variable geometry factor etc.). Furthermore, the thoron (220Rn) suppression unit was applied to eliminate the thoron additional signal by its radioactive decay in the retarding piping system, inserted in the close circuit. The comprehensive series of testing and calibration experiments were carried out in a laboratory environment.
The experimental device can be used for different measurement procedures, concerning two major branches of applications.
For the field applications, the continuous in-situ measurement of soil-gas radon concentration can be provided with regards to the study of earthquake prediction and investigation of ground water level fluctuations. For the indoor applications, the measurement system can be applied for continuous recording of radon concentration in samples taken from cracks and leakages in building constructions in contact with subsoil (the radon diagnosis method). The dynamical measuring range is sufficient for monitoring of indoor environment with high content of radon (caves, mines, underground workplaces, basements etc.). The system description including applied experimental conditions will be presented and some first results of in-situ measurements will be reported.