Predrag Ujic

Various imported building materials commonly used in construction and industry in Serbia were analyzed using gamma spectrometry. Based on the activity concentrations of 226Ra, 232Th, and 40K in the investigated samples, radium equivalent activity, Raeq, absorbed dose rate, D, annual effective dose, DE, and the external hazard index, Hex, were calculated to assess the radiation hazard for people. The Raeq for most of the analyzed samples (416 in total) was lower than the maximum admissible value of 370 Bqkg-1 set in the UNSCEAR report. The absorbed gamma dose rate in air was found to vary from 0.030 mGyh-1 to 1.328 mGyh-1 which in some cases exceeded indoor dose rates in Europe. The obtained values for annual effective dose exceed the limits of 0.41 mSv given in literature for about 5 % of measured samples, while values of Hex were higher than unity for three samples of cement, eight samples of granite, and one sand sample. As a possible source of elevated effective dose, the radon exhalation from building materials was estimated using the parameters given in literature. The internal dose due to 222Rn exhaled from the building material was found to be up to nine times higher than external dose due to 226Ra content in some cases.

The main contribution to population exposure is due to radon and thoron progenies and not radon itself. The aim of this study was therefore to estimate annual effective dose using the results of Direct Radon and Thoron Progeny Sensors were exposed in 69 selected schools and 319 dwellings in several regions of Balkans: in Serbia: regions of Sokobanja and Kosovo and Metohija, Republic of Macedonia, Republic of Srpska and Slovenia. Obtained average total effective doses are in the range from 0.22 mSv a(-1) (schools in Republic of Srpska) to 2.5 mSv a(-1) (dwellings in Kosovo) and are below the reference level of 10 mSv a(-1) recommended by International Commission on Radiological Protection.

It is indicated that the exposure to radon originating from the building materials is not negligible and the radon exhalation measurement should get more attention in the future. The experience with four different methods of the exhalation measurement, established in our laboratory for the purpose of the intercomparison is reported. Additionally, a comparison of advantages and disadvantages of used methods is discussed.

Radon problem has a special attention in many countries in the world and the most of them have established national radon programmes. The radon issues in Serbia have not been approached in a systematic and organized way. Currently, there are many research groups and institutions working in radon field, and it is a good basis to integrate all these activities into a comprehensive national programme to define the strategic objectives and action plan for the next few years. Also, Serbia as a candidate for membership in the EU is obliged to harmonize its legislation, including the field of radiation protection in which the radon issues has an important role. In this report, a brief history of radon research, present status and plans for the future activity on radon issues in Serbia are presented. Regarding the long-term plans, the establishment and implementation of the Radon Action Plan with the primary goal of raising awareness about the harmful effects of public exposure to radon and implementing a set of measures for its reduction. In that sense, the synergy between the national, regional and local organizations responsible for public health and radiation protection must be achieved.