Radon in soil gas - investigation and data standardization at radon reference sites, Czech Republic
|Location||International Geological Congress,oslo 2008|
|Holding Date||11 October 2008|
Radon risk mapping at building sites in the Czech Republic indicates an advisable level of protection of buildings against the penetration of radon from the geological basement. The radon index, defined by the Act No. 18/1997 (Atomic Law), derives from a set of measurements of radon (222Rn) activity concentration in soil gas at a depth of 0.8 metres, and an estimate of the gas permeability of soil. The adopted system classifies the radon index of a site into three categories: low, medium, and high. Measurements of radon in soil gas differ in the techniques used for soil gas sampling, the use of diverse instrumentation, the modes of data processing, and by the various technical approaches used by individuals and organizations. Since the method of construction to protect a house against the penetration of radon from the geological basement evolves from the radon index, the uniformity of its determination is a fundamental requirement.
Radon data standardization in the Czech Republic is based on instrument calibration at the national radon chamber, and on comparison measurements at radon reference sites. Three new radon reference sites with distinct radon in soil gas levels, Cetyne (32 kBq/m3), Bohostice (52 kBq/m3), and Buk (155 kBq/m3), have been established in central Bohemia, the Czech Republic, in 2000. Each reference site comprises 15 fixed stations. The radon comparison measurement is carried out in a group of organizations. An Excel PC programme, TestMOAR, performs the analysis of the test data by comparing the group and using radon database of the reference sites. As of September 2007, 135 radon comparison measurements at the natural radon reference sites, acquired by organizations performing radon risk mapping at building sites in the Czech Republic, have been evaluated.
Radon reference sites also serve for investigation. A series of targeted measurements comprised studies of temporal variations of radon activity concentration in soil gas, the distribution of radon activity concentration in soil gas at reference sites, the effect of random soil air sampling at reference sites, the dependence of radon activity concentration in soil gas on meteorological parameters, radon activity concentration and perforation of soil, and the transfer of soil gas samples into the detector (Lucas cell) through a micro-filter. Studies performed at radon reference sites in the period 2000—2007 have demonstrated the precision of radon measurements, the sites characteristics, and contribute to a general knowledge of radon in soil and the reasonable assessment of radon test results.