The Preliminary Study On Radiation Source Terms And Environmental Affection Of A Radiation Abnormal Area In An Airborne Radioactivity Survey

The Ministry of Environment Protection had organized an airborne radiometric survey for a nuclear facility in Hengyang in2014.But the result show that there is an area,located in its southwest and in the upper reaches of Xiang-Jiang River, where the ? radioactive level is abnormal. Through the investigation, the staff identified the region as a retired copper ore. With the concerns of non-uranium mines(NORM)radiation environmental impaction, it is necessary to ascertain the status of radiation levels in the retired copper mining area and its effects on the quality of the Xiang-Jiang River and the residents lived around.This soil survey focused on the mining area?the tailings area and the tailings areas where is covered with soil to grow crops(the farmLand in the full-text), and in order to measures the activity concentration of226Ra?232Th and 40 K in these area. The results of the soil analysis:(1)The activity of 226Ra?232Th and 40 K of the soil in the mining area are1.42?1.51 and 1.52 times of the average levels of the Hunan province;(2)The activity of the 232 Th and 40 K in the tailings area are lower than the average level of Hunan province,but the content of 226 Ra is 2.18 times of the average concentration;(3)The activity of 226Ra?232Th and 40 K of the soil in the farmLand are 1.17?6.15 and 1.77 times of the average levels of the Hunan province.The assessment result of the ? radiation level of the environment show:(1)The calculated value of ? radiation absorbed dose rate on the1 m high off the ground(D?)in the mining area?the tailings area and the farmLand area are separately 1.67?1.20 and 3.28 times of average level of Hunan province;(2)The annual effective dose of the retired copper ore are all lower than 460?Sv·a-1 which is a normal level recommended by the UNSCEAR;(3)The Radium equivalent activity(CRaeq)in the mining area and the tailing area are both lower than the limited value 370Bq·kg-1,but the concentration in the farmLand area is 1.40 times of the cut-off level;(4) The internal radiation index and the external radiation index of the mining area and the tailing area are lower than the limits 1recommended in ? Limits of radionuclides in building material ? GB6566-2010, but the internal and external radiation indexes in the farmLand area are 1.82 and 1.42 times of the limits.The radionuclides levels in the water of the study area are follows:(1)The concentrations of the U?Th?226Ra and 40 K in the mine water used by the inhabitants are separately 16.92?9.20?1.64 and 5.64 times ofthe average level of the well water in Hengyang;(2)The levels of the 4nuclides of the tailing-water are all higher than the yearly mean levels of the Xiang Jiang River, and are the 79.73?9.40?2.52 and 4.05 times of the average levels of the Xiang Jiang River, and the uranium content is higher than 0.1 mg·L-1 in?Emission Standards of Pollutants from Rare Earths Industry?GB26451-2011;(3)The tailings seepage water is discharged into the stream and the concentration of the radionuclides are diluted, but the concentrations of the U?Th?40K are still higher and are 1.60?2.68?3.05 times of the average level in Xiang Jiang;(4)After the small streams flowing into the downstream river, the concentration of the U?226Ra are both lower than the average level of Xiang Jiang river and but the radionuclides level of the Th?40K are still separately 1.46 and 2.99 times of the Xiang Jiang River levels;(5)The tailing water flowing through the stream and river and eventually flow into the Xiang Jiang River. By the analysis of the water of the final location in Xiang Jiang, the results shows that the concentration of the Th?40K are higher than the average level of the Xiang Jiang river, but the levels of U?Th?226Ra and 40 K in the samples of upstream and downstream are all lower than the previous investigation levels.(6)With the investigation of the concentration of210 Po in the study area, just the concentration of the total tailings seepage water and discharged into streams water are higher than the average level of national main rivers and are about 2.2 times and 1.53 times of thesurvey value;(7)The concentration of the 210 Pb of the study area are all higher than average level of the river water and well water in our country,which had been studied by some professors. The results show that the mine water concentration was 2.58 times of the value level of the census,and the 210 Pb concentration in other waters are 2.83~5.60 times of the value level of the national census.