Radon situation at the districts of uranium legacy and its risks

Full text: In the last years a radiation hazard of the radon and its disintegration progenies in the world is widely discussed. Natural sources of radon can be soil, parent rocks, ground water, tails and wastes of the uranium ore conversion and mining, and contamination of some building materials. The hazard of radon for human health is not only connected to radon dose rates, but it depends on exposition period and age of the people exposed. It is obvious that the lung cancer risk decreases with age of people, but this risk increases about 10 times for smoking peoples. Central Asian Countries were the main supplier of the uranium in former USSR, and mining activity and conversion of uranium ores had resulted in accumulation of large amounts of radioactive waste. Presently, it is an exigent problem to provide radiation safety on the territories of uranium mines, rock debris deposits, tails and closely located settlements. In this work, results of measurements of the radon levels on the territories of former uranium mines and nearby located populated sites are presented. For radon measurements, the electronic devices of RRA-01M (Russia) and PRM-145 (Slovenia) based on semiconductor detector and scintillation cells, respectively, were used. Both devices record alpha particles of daughter radionuclide Po-218. For reliable estimation of the efficient annual doses (EAD) of inhabitants and its fatal factor risks (FFR) a long-term registration of alpha particles from radon was carried out by using nuclear solid track detectors CR-39 (Italy). Living premises and offices were arbitrarily selected, and radon exposure was measured with CR-39 for three months at summer and winter time. In Yangiabad settlement, the volume activity of indoor radon was - 60-100 Bq/m3, values of EAD of radon for inhabitants 1.7-2.8 mSv/year (at permissible limit of 5.0 mSv/year) and FFR estimation at (1.3 - 2.3) x10-4. In Chorkesar village, at windless day and morning period the radon activity on territory of the mine reached 70-100 Bq/m3 at the distance of 50-70 cm from the ground level. Indoor radon level ranged from 60 to 450 Bq/m3 and for EAD was 1.7-12.6 mSv/year, FFR was (1.3- 10.5)x10-4 at summer time and from 250 to 1200 Bq/m3 and for EAD was 7.0-33.6 mSv/year, FFR was (5.6-27) x 10-4 at winter time. The radon hazardous sites with activity more than 2000 Bq/m3 have been discovered. In Krasnogorsk settlement, effective annual dose of radon does not exceed an permissible limit and it is found within 0.5-2.8 mSv/year. (authors)