ON THE ISSUE OF RADON EXPOSURE IN THE EXISTING RADIATION SITUATION AT WORKPLACES

Abstract

Objective: assessment of probable exposure levels from radon and NORM in workplaces within the context of justi fying radiation protection plans in an existing exposure situation.

Materials and methods: Materials regarding the assessment of naturally occurring radioactive material (NORM) con tent in tailing from mining and processing industries in Ukraine and assessments of contamination levels of industri al sites of oil and gas enterprises were used for estimating the probable range of effective doses (ED) of workers fromNORM at industrial enterprises. These materials were obtained as a result of research conducted by specialists from theRadiation Protection Laboratory of the State Institution «O.M. Marzіeiev Institute for Public Health of the NationalAcademy of Medical Sciences of Ukraine» (RP SI «IPH NAMSU»). The results of studies conducted by the StateInstitution «Ukrainian Scientific Research Institute of Industrial Medicine» (SI «UKRMEDPROM») were used for calcu lating the EDs of iron ore miners. Calculations of probable EDs of industrial enterprise workers were carried out usingmethodologies and recommendations from publications of the IAEA related to occupational exposure. Assessments ofexposure levels for office workers were based on measurements of indoor radon concentrations of first-floor premisesin multi-story buildings of industrial urban development from the laboratory's own databases. Radon measurements inindoor air were conducted using passive track etch radon detectors with an exposure time of at least 30 days.Calculations of EDs for office workers were carried out using dose coefficients and mathematical models from the ICRP.

Results: When workers are exposed to radon as a result of the technological process, radiation exposure is limitedby dose criteria. Using non-uranium miners as an example, it was shown that effective doses (ED) due to gammaradiation varied within a narrow range, ranging from 0.2 to 0.4 mSv/year, and were on average an order of magnitudelower than the radon component of the total ED for the two groups of mines, which amounted to 2.0-14.0 mSv/yearfor the Northern group and 0.3-0.8 mSv/year for the Southern group. For three underground worker specialties, radi ation EDs could potentially exceed the reference level of 6 mSv/year and fall under regulatory control. Potentialradiation EDs for workers at one of the Ukrainian oil fields were generally not significant (<0.1-1 mSv/year), exceptfor areas where used pipe storage and sludge settlers were located (70.0 mSv/year; 28.0 mSv/year at a distance of10 meters), near which dose limits for Category A personnel (6 mSv/year), falling under regulatory control, wereexceeded. Radon exposure in workplaces also includes the presence of workers in regular office premises on the firstfloors of multi-story buildings, where the main source of radon entry into the air is the underlying soil. For the mostresearched regions of Ukraine (~1200 measurements of radon activity concentrations in first-floor premises), it wasfound that the reference level of 300 Bq/m3 is exceeded in 0.2-0.5% of cases in certain regions, indicating thatpotentially the reference level may be exceeded in tens of thousands of premises.

Conclusions: A differentiated approach is justified for assessing the hazards of workplaces, allowing for optimizingradiation protection for workers at a reasonable cost and saving significant resources for enterprises. Effective doses(ED) of radiation for workers at enterprises where radon is an integral part of the technological process vary widelyand can differ by an order of magnitude even within the same enterprise. Reference levels of 300 Bq/m3 may beexceeded in tens of thousands of office premises, and only through direct measurements of radon activity concen trations in building air can such premises be identified.

Keywords: effective exposure dose of workers; existing exposure situations; exposure in workplaces; indoor radon.