Забруднення 137Cs деревної золи у північних районах Житомирської області

Abstract

Due to changes in the economic situation in Ukraine, high cost for many segments of the population of natural gas and electricity, residents of different regions are switching to the use of fuel wood of local origin for heating buildings and meeting other economic needs. Today, the process of harvesting fuel wood is often completely spontaneous, that is, the population carries wood harvesting in any accessible places, ignoring the possible negative consequences. The given problem in the absence of state regulation, in addition to the legal aspect, is complicated by the radioactive contamination of forest lands in which uncontrolled harvesting by the population of fuel wood with unknown levels of radionuclide content is carried out. This problem is especially relevant in the Polissya regions of Ukraine, whose forest areas have suffered from the largest radioactive contamination as a result of the Chernobyl accident. Thus, the area of forests with a density of soil contamination with 137 Cs of above 37 kBq / m 2 , in which restrictions on forest use were introduced in Zhytomyr, Rivne, Kyiv oblasts, respectively, accounted for 60%, 56%, 52%, and in the Volyn and Chernihiv oblasts such plantations accounted for about 20% of the total area of the forest fund. Today, the bulk of wood products (fuelwood) does not exceed GNPAR-2005 by 137 Cs (600 Bq / kg) and 90 Sr (60 Bq / kg), but the situation may change for some of the territories contaminated with radionuclides (the northern part of Zhytomyr and Kyiv oblasts) , because in recent years the accumulation dynamics of 137 Cs has negative tendencies for all wood species, an increase in the activity of 137 Cs in the majority of the components of the woodland and the growth of the total content of radionuclides in the wood is observed. As a result of the increase in radioactive contamination of forest stands, the risk of fuel wood harvesting with the levels exceeding GNPAR-2005 by 137 Cs and 90 Sr content has increased recently in the Polissya region of Ukraine, and cases of use of heating fuel for private fuel wood buildings with significant levels of radionuclide contamination are increasing. Wood is a relatively low-salt fuel, the average values of ash content of wood in most of the rocks are in the range of 0.3-1%, therefore, when burning contaminated with radionuclides of wood, because of low ash content of this fuel, the concentration of radionuclides in the mineral part of the waste (ash) is increased with the increase of the specific activity of ash in 50-100 times in comparison with the specific activity of the original wood. Results of the study of contamination level of wood ash with 137 Cs in private farms of settlements in the northern part of Zhytomyr region, performed in 2017, have been analyzed. As a result of the analysis of 154 samples by the gamma spectrometry method, it was found that the 137 Cs specific activity ranged from 170 to 32900 Bq/kg in wood ash, formed during the burning of contaminated wood fuel in wood-fired ovens in private farms of this region. Generalized data on relative distribution of the wood ash samples of the studied settlements by the value of 137 Cs specific activity is presented in the article. According to the Basic Sanitary Rules of Ukraine-2005, using 137 Cs specific activity as a criterion, 9 % of the total number of ash samples, collected in private farms of the monitoring network, can be considered as low-level radioactive waste, in particular: 3.9 % of ash samples, collected in the Bigunsky Village Council; 7.1 % of ash samples, collected in the Mozharovsky Village Council; 7.7 % of ash samples, collected in the Pischanitsky Village Council and 22.7 % of ash samples, collected in Narodychi town. Obtained data indicate that contaminated with radionuclides wood ash is an additional factor of radiation hazard, since it is a potential source of additional external and internal exposure for local population. Key words : wood ash, 137 Cs, specific activity, radioactive waste