Radionuclides Content in Pasteurized Cow Milk: Dose Estimation.

Results from the radiological monitoring of 46 pasteurized cow milks for the period of 2011-2015 are presented. The activity of 137Cs, 90Sr, 226Ra, 40K, 210Pb, 232Th and natural U was determined by gamma spectrometry for gamma emitters and by radiochemical separation for 90Sr. The maximum obtained results are 0.449 ± 0.016 Bq/l (137Cs), 0.105 ± 0.020 Bq/l (90Sr), 1.63 ± 0.16 Bq/l (226Ra), 53.1 ± 1.6 Bq/l (40K), 1.01 ± 0.30 Bq/l (210Pb), 0.05 ± 0.07 Bq/l (232Th) and 0.14 ± 0.12 mg/l (natural U). Annual Effective Dose from the ingestion of above-mentioned radionuclides was estimated on the basis of the consumption for adults and children (1-2 y) applying two models-realistic and conservative. The values for the Ingestion Dose vary from 0.02 mSv/y to 0.05 mSv/y (adults, realistic model) and from 0.06 to 0.15 mSv/y (adults) and from 0.15 to 0.87 mSv/y (children 1-2 y old) from conservative model. For bought models, the main contribution to the Ingestion Dose, instead of 40K, is due to the 210Pb and 226Ra. Three hypotheses are given for the 226Ra content in pasteurized cow milk. The received results demonstrate the need of determination of artificial and natural radionuclides in cow milk.

Radiological impact of surface water and sediment near uranium mining sites.

The aim of this study is to assess the radiological impact of surface water and sediment around uranium mining sites 20 years after their closing. The areas under observations are 31 former classical underground uranium mining and exploratory sites in Bulgaria, named as objects. The extraction and processing of uranium ores in the Republic of Bulgaria were ended in 1992. To assess the radiological impact of radionuclides field expeditions were performed to sample water and bottom sediment. The migration of uranium through surface water was examined as one of the major pathways for contamination spread. The range of uranium concentration in water flowing from the mining sites was from 0.012 to 6.8 mgU l(-1) with a geometric mean of 0.192 mgU l(-1). The uranium concentrations in water downstream the mining sites were approximately 3 times higher than the background value (upstream). The concentrations of Unat, (226)Ra, (210)Pb, and (232)Th in the sediment of downstream river were higher than those upstream by 3.4, 2.6, 2, and 1.7 times, respectively. The distribution coefficient of uranium reflects its high mobility in most of the sites. In order to evaluate the impact on people as well as site prioritization for more detailed assessment and water management, screening dose assessments were done.

Natural radioactivity content in Bulgarian drinking waters and consequent dose estimation.

Natural radioactivity in drinking water from Bulgaria was determined in 994 samples. Nine hundred and seventeen of them are from the Southwestern part of the country. The measured activity of natural uranium, (226)Ra, gross alpha and gross beta activity varied from 20 (5) ng l(-1) to 0.11 (3) mg l(-1), MDA to 0.39 (6) Bq l(-1), MDA to 6.23 (39) Bq l(-1) and 0.030 (7) Bq l(-1) to 0.98 (22) Bq l(-1), respectively. Approximately 33% of the investigated waters exceeded a gross alpha activity of 0.1 Bq l(-1), 1.8% a natural uranium concentration of 0.03 mg l(-1) and 1% an (226)Ra concentration of 0.15 Bq l(-1). Annual effective dose from natural radionuclides ranges from 0.0175 (43) µSv to 95.5 (2.6) µSv. Median values of the contribution of the (226)Ra and uranium to the indicative dose are 10.22 and 0.21 µSv y(-1), respectively. Poor relationships between (226)Ra/nat.U (r, 0.12) and for gross beta activity/natural uranium (nat.U) (r, 0.29) were observed. The relationships between nat.U/gross alpha activity (r, 0.50) and for gross alpha activity/gross beta activity (r, 0.52) concentration distributions were stronger.