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Continuous diurnal radon measurements in Bulgarian caves and dose assessment

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Abstract

Bulgaria is a country in the eastern part of the Balkan Peninsula, in South-eastern Europe. The presence of many mountains and karst areas is a prerequisite for a large number of caves in the country, but only some of them are managed and accessible to tourists. The purpose of the study is continuous measurement of radon concentration in six popular Bulgarian tourist caves (Bacho Kiro, Magura, Venetsa, Saeva dupka, Snejanka, and Uhlovica), and analysis of the diurnal variation. The direct, continuous radon measurements were performed with TERA (TSR4) system (Tesla, Czech Republic). 29 radon concentration time series were considered for evaluation of radon variations during the day and night. The period of the measurement was the autumn of 2019, and only one cave (Bacho Kiro Cave) was measured during the winter. The measurements were performed at different points (gallery, halls, or other cave formations) in each of the caves. The average diurnal radon concentration in the different caves varied from 531 Bq m−3 (Magura cave) to 5472 Bq m−3 (Venetsa cave). The variation of radon concentration between distinct places in most caves was approximately 1–2 k Bq m−3. No significant difference in radon concentrations was observed between night and day in a 24–96 h period measurement. The large fluctuations between the values measured at the entry (10–640 Bq m−3) and exit (165–927 Bq m−3) compared to those inside the cave were found only in cave Magura. The radon exposure of workers and visitors was assessed, using long-term measurements in the caves, based on the ICRP recommendation.

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Data availability

The datasets generated during and analyzed during the current study are available from the corresponding author on reasonable request. Data from passive measurements of radon concentration in caves are available at link https://www.sgem.org/index.php/elibrary-research-areas?view=publication&task=show&id=8340.

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Acknowledgements

The study is supported by the National Research Fund under contract №КП-06-23/1/17.12.2018. The team is very grateful to the administrative management of the caves and the tour guides.

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Authors and Affiliations

  1. National Centre of Radiobiology and Radiation Protection, 3 Georgi Sofiyski, Str., 1606, Sofia, Bulgaria

    B. Kunovska, K. Ivanova, D. Djunakova, N. Chobanova & J. Djounova

  2. Faculty of Medical Sciences, Goce Delcev University of Stip, 10-A Krste Misirkov St., 2000, Stip, Republic of North Macedonia

    Z. Stojanovska

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  1. B. Kunovska
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Correspondence to B. Kunovska.

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Kunovska, B., Ivanova, K., Djunakova, D. et al. Continuous diurnal radon measurements in Bulgarian caves and dose assessment. Eur. Phys. J. Spec. Top. 232, 1617–1623 (2023). https://doi.org/10.1140/epjs/s11734-023-00874-w

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