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2 2010

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Seasonal variation of radon in the Bozkov cave

Rovenska K., Thinova L.

Nukleonika

2010

Vol. 55, No. 4

483-489

Measurement of the radon concentration has been performed in the Bozkov dolomite cave since 2002. Radon concentration was obtained by two means: continuous measurement by a Radim3 monitor at 30 min intervals and a 6 month average by LR115 solid-state nuclear track detector (SSNTD) in a diffusion chamber placed at 8 points along the cave tour path. The radon concentration shows diurnal, seasonal, and yearly variations. The concentration maximum in the cave, in contrast to the dwellings, occurs in the summer time and equals to thousands of Bq/m3. At the same time, high variability of radon concentration occurs. Statistical analysis of a long time series of radon concentration was performed and the meteorological data were taken into account. The annual effective dose from radon for the cave guide (2006 y, working time spent in the cave 414 h) was 3.05 mSv. The dose was calculated using the mean value of radon concentration obtained by SSNTD as written above.

Environmental and radon measurements in the underground workplaces in the Czech Republic

Thinova L., Rovenska K., Otahal P.

Nukleonika

2010

Vol. 55, No. 4

491-493

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.