Seasonal variation of radon in the Bozkov Cave

Most of radon and other environmental measurements were carried out in connection with research focused on improvement of radon dose assessment in the underground workplaces in the Czech Republic. The following methods are very useful for the detection of radon sources: air flow measurement; continual and short volume activity of radon and its progeny measurement; volume activity of thoron measurement; mapping of radon level in all workplace areas including horizontal and vertical gradient; radon in water measurement; integral radon monitor RAMARN testing, etc. In conjunction with equilibrium radon concentration (ERC) monitoring studies were conducted of radiogenic characteristics of caves clastogene and carbonate sediments, and other rock formations present in the Czech Massif and Western Carpathian. Over 150 samples of cave sediments were collected, in which the mass activities of present radionuclides were determined. Spectrometric analysis of the sediments enabled monitoring of disturbance in secular radioactive equilibrium in the given geochemical systems, through evaluation of 238U/226Ra or 228Th/224Ra proportion. Ratio of 208Tl/226Ra was monitored for the rock groups from the origin point of view assessment. Typical values for such ratio for carbonate rocks (including amphibolite and erlan) varied between 0.2-0.5, while for clastogene sediments and crystalline limestone the typical values were in the range 1.4-1.6. Conclusions from measurements were implemented in the new methodology for radon dose assessment. (authors)