RADIATION CONDITIONS IN KALUGA REGION 30 YEARS AFTER CHERNOBYL NPP ACCIDENT

Abstract

The article describes radiation conditions in the Kaluga region 30 years after the Chernobyl NPP accident. The Chernobyl NPP accident caused radioactive contamination of nine Kaluga region territories: Duminichsky, Zhizdrinsky, Kuibyshevsky, Kirovsky, Kozelsky, Ludinovsky, Meshchovsky, Ulyanovsky and Hvastovichsky districts. Radioactive fallout was the strongest in three southern districts: Zhizdrinsky, Ulyanovsky and Hvastovichsky, over there cesium-137 contamination density is from 1 to 15Ci/km. According to the Russian Federation Government Order in 2015 there are 300 settlements (S) in the radioactive contamination zone, including 14 settlements with caesium-137 soil contamination density from 5 to 15 Ci/ km2 and 286 settlements with the contamination density ranging from 1 to 5 Ci/km2. In the first years after the Chernobyl NPP accident in Kaluga region territories, contaminated with caesium-137, there were introduced restrictive land usage, were carried out agrochemical activities (ploughing, mineral fertilizer dressing), there was toughened laboratory radiation control over the main doze-forming foodstuff. All these measures facilitated considerable decrease of caesium-137 content in local agricultural produce. Proceeding from the achieved result, in 2002 there took place the transition to more tough requirements SanPiN 2.3.2.1078-01. Analysis of investigated samples from Zhizdrinsky, Ulyanovsky and Hvastovichsky districts demonstrated that since 2005 meat samples didn’t exceed the standard values, same for milk samples since 2007. Till the present time, the use of wild-growing mushrooms, berries and wild animals meat involves radiation issues. It was demonstrated that average specific activity of caesium-137 in milk samples keeps decreasing year after year. Long after the Chernobyl NPP accident, the main products forming internal irradiation doses in population are the wild-growing mushrooms and berries. Population average annual effective doses, caused90by Chernobyl fallouts, do not exceed 1 mSv/year. In 2014 AAEDmaximum calculated value for adultpopulation of 0,91 mSv was established in the following settlements:, Martynki village(Ulyanovsky district) and Lovatyanka village (Hvastovichsky district). The doses, accumulated in the period after the accident, are generally not high. According to calculations numerical value of forecasted accumulated doses varies from 0,23 to 21 mSv. Maximum calculated values of 21 mSv are established in Hvastovichsky district (Lovatyanka village) and Ulyanovsky district (Martynki village). Between 1986 and 2005, the effective irradiation doses did not exceed 29 mSv. Hence, in 70 years after the Chernobyl NPP accident standard value of 70 mSv will not be exceeded in the Kaluga region settlements. After 30 years, the main cause of population internal exposure is consumption of products from private subsidiary farms and especially of wild-growing products. There was conducted radiation monitoring of local agricultural foodstuff produce and of products from the forest. It demonstrated that caesium-137 average specific activity in samples of milk from private subsidiary farms in settlements of Zhizdrinsky, Ulyanovsky and Hvastovichsky districts decreased several-fold. It is between 20,0 Bq/l in 2007 and 1,7 Bq/l in 2015. In 2015, maximum levels of caesium-137 contamination in milk was 3,1% of the standard value, in potatoes - 4,7%, in meat - 4,4%.Average specific activity of caesium-137 in forest mushrooms samples from Zhizdrinsky, Ulyanovsky and Hvastovichsky districts doesn’t decline. Peaks of average caesium-137 activity were observed in 2012, 2013 and 2014; they depend on mushrooms abundance, species, dry summer weather and locations of sampling in the forest. In 2015 in three southern districts, the maximum content of caesium-137 in mushrooms exceeded the permissible level (500 Bq/kg) 4,5-fold; about 2% of the samples do not correspond to it. The maximum contamination of berries with caesium-137 also exceeds the permissible level (160 Bq/kg) nearly 5-fold, and about 43% of samples don’t correspond to it. Obtained results have demonstrated that long after the Chernobyl NPP accident (30 years) the main part of population internal exposure is caused by consumption of wild- growing mushrooms and berries. In the recent years, milk consumption does not play a considerable role in forming of internal dose any more. Conclusion: in 30 years since Chernobyl NPP accident in the Kaluga region radiation and environment conditions have considerably improved on the territories with radionuclides contamination. However, problems remain. The major task for mitigation of the Chernobyl NPP accident consequences is comprehensive radiation, social and economic rehabilitation of the contaminated territories.