Janja Vaupotič

Systematic indoor radon and gamma-ray measurements in Slovenian schools.

Abstract—During the winter months of 1992/93 and 1993/94, instantaneous indoor radon concentrations and gamma dose rates were measured in 890 schools in Slovenia attended in total by about 280,000 pupils. Under “closed conditions,” the room to be surveyed was closed for more than 12 h prior to sampling, the air was sampled into alpha scintillation cells with a volume of 700 cm3, and alpha activity was measured. An arithmetic mean of 168 Bq m−3 and a geometric mean of 82 Bq m−3 were obtained. In 67% of schools, indoor radon concentrations were below 100 Bq m−3, and in 8.7% (77 schools with about 16,000 pupils) they exceeded 400 Bq m−3, which is the proposed Slovene action level. In the majority of cases, radon concentrations were high due to the geological characteristics of the ground. Approximately 70% of schools with high radon levels were found in the Karst region. Gamma dose rates were measured using a portable scintillation counter. An arithmetic mean of 102 nGy h−1 and a geometric mean of 95 nGy h−1 were obtained. No extraordinarily high values were recorded.

Systematic indoor radon and gamma measurements in kindergartens and play schools in Slovenia

Systematic measurements of indoor radon concentrations and gamma dose rates were carried out in the 730 kindergartens and play schools in Slovenia that, together, care for 65,600 children. The main method for indoor radon measurement was direct sampling in alpha scintillation cells, but in cases with an increased instantaneous radon concentration, the additional methods of track-etch detectors and alpha spectroscopy were applied. In 528 kindergartens and play schools (72%), radon concentrations were below 100 Bq m-3, with a geometric mean of 58 Bq m-3. In 16 kindergartens and play schools (2.2%), radon concentrations exceeded 800 Bq m-3. In all cases, the main reason for a high indoor radon concentration was the geological structure of the soil. Gamma dose rates were measured with a portable scintillation counter, but in the Ljubljana region thermoluminescence dosimeters were also exposed. The results ranged from 30 to 295 nGy h-1, with a geometric mean of 88 nGy h-1.

Natural radioactivity of fresh waters in Slovenia, Yugoslavia

Abstract The radioactivity of surface and ground waters in Slovenia, Yugoslavia, was assayed. About 700 samples of surface and 500 samples of ground waters were analyzed for 222 Rn, 226 Ra, natural uranium, and gross beta activity. In surface waters the highest concentrations found were 5365 Bq m −3 , 92 Bq m −3 , 215 Bq m −3 , and 0.4 mg m −3 for radon, radium, gross beta, and uranium, respectively. In surface waters the radioactivity is higher in the region of uranium ore deposits, in the vicinity of a phosphate processing plant, and in the region rich in thermal and mineral waters.

Soil radon monitoring in the Krsko Basin, Slovenia.

In order to support the safe operation of the Krsko Nuclear Power Plant (Westinghouse, 676 MWe PWR), the seismotectonic structure of the Krsko basin has been thoroughly investigated. As part of a wider study, a study on radon in soil gas was started in April 1999. Combined barasol detectors buried in six boreholes, two along the Orlica fault and four on either side of it, measure and record radon activity, temperature and pressure every 60 min. The results have been evaluated and the possibility of a correlation with seismic activity is discussed. Correlation between radon concentration and barometric pressure has been observed for all barasols. Preliminary results show that, at one location, the correlation coefficient between radon and barometric pressure changed sign before earthquakes.

Nanosize radon short-lived decay products in the air of the Postojna Cave

At two points in the Postojna Cave, short-term monitoring in summer and in winter of air concentrations of radon and radon decay products, equilibrium factor, unattached fraction of radon decay products (f(un)), barometric pressure, relative air humidity in the cave and air temperature in the cave and outdoor has been carried out, with the emphasis on f(un). Dose conversion factors, calculated on the basis of f(un) values obtained (ranging from 0.09 to 0.65) exceed 5 mSv WLM(-1), by a factor of 11.5-14.0 in summer and of 3.0-4.0 in winter for mouth breathing, and 3.1-3.5 in summer and 1.5-1.7 in winter for nasal breathing.

Alpha scintillation cell for direct measurement of indoor radon

Abstract A large volume (1500 cm3) alpha scintillation cell to measure indoor radon is described. Air is sampled directly into the cell and gross alpha activity is measured after three hours. The cells are suitable for concentrations higher than 10–20 Bq/m3. They were successfully used for radon measurements in kindergartens in Nova Gorica.

Long-term radon investigation in four selected kindergartens in different geological and climate regions of Slovenia

During a one year-and-a-half period in 1993 and 1994 indoor radon concentrations were measured with complementary measurement techniques in four selected kindergartens in different geological and climate regions in Slovenia. This study was performed to obtain more information how local geology, climate, building materials and occupational patterns affect radon concentration in a kindergarten. In addition, the advantages and disadvantages of different measurement techniques were critically appraised. It was found that average working hours radon concentrations, calculated on the basis of continuous radon measurements, are significantly lower than whole day averages obtained by track-etch detectors. The ratio might be as large as two.

Radon and thoron doses in kindergartens and elementary schools

Exposing the Raduet Rn-Tn solid-state nuclear track detectors, radon (Rn: (222)Rn) and thoron (Tn: (220)Rn) activity concentrations have been measured in 7 kindergartens and 18 elementary schools in Slovenia. Diurnal variations of both gases were monitored using a Rad7 device. The Rn concentration was in the range from 145 to 794 Bq m(-3) in kindergartens and from 70 to 770 Bq m(-3) in schools, and the Tn concentration was in the range from 21 to 73 Bq m(-3) in kindergartens and from 4 to 91 Bq m(-3) in schools. The Tn versus Rn concentration ratio varied from 0.02 to 0.83. Monthly effective doses due to radon and its decay products ranged from 109 to 600 μSv month(-1) in kindergartens and from 21 to 232 μSv month(-1) in schools, and those due to thoron and its decay products ranged from 3.8 to 13.3 μSv month(-1) in kindergartens and from 0.29 to 6.62 μSv month(-1) in schools. The contribution of thoron to the total effective dose was from 1.3 to 11 % in kindergartens and from 0.4 to 17 % in schools.

Radon Exposure At Drinking Water Supply Plants In Slovenia

Abstract— Radon was measured at ten drinking water supply plants in Slovenia, in rooms attended by workers. Concentrations ranged from 40 to 2600 Bq m−3 resulting in annual effective doses of the personnel, calculated according to the ICRP 65 methodology, of below 0.5 mSv at 6 places, and of 0.6–3.0 mSv at the others. In addition, at each plant water was analyzed for 222Rn and 226Ra and ranges of 0.5–33 kBq m−3 and 5–34 Bq m−3, respectively, were obtained.

Systematic survey of natural radioactivity of soil in Slovenia

Soil samples, from 70 points uniformly distributed over entire Slovenia, were analysed for (40)K, (232)Th and (226)Ra using gamma spectrometry, and for (234)U and (238)U using alpha spectrometry. The following ranges and averages of activity concentrations (Bq kg(-1)) were obtained: 98-2600 and 800 ± 520 for (40)K, 9-170 and 77 ± 33 for (232)Th, 12-270 and 63 ± 44 for (226)Ra, 12-84 and 34 ± 19 for (234)U, and 11-90 and 34 ± 19 for (238)U. With respect to lithology, the highest average values for (40)K and (232)Th were found at clastic sediments containing clay and for (226)Ra on carbonate rocks. Based on the measured activity concentrations, terrestrial gamma dose rates were calculated. The total dose rate ranged from 15 to 260 nGy h(-1), with arithmetic mean of 110 ± 49 nGy h(-1), being the highest over carbonates.