Based on the natural radiation environmental geological survey in the middle east part of Wulian County,the author analyzed the characteristics, distribution and influencing factors of radioactivity. The results show that, in the natural radioactive background of the investigation area, the background value of γ-radiation dose rate is 80.0 nGy/h,and the average annual effective dose of public exposure is 0.46 mSv. The high background area of natural radiation is mainly expressed by the abnormal characteristics of γ-radiation dose rate and the radionuclide 232Th content,and its main lithology includes monzogranites and biotite monzonitic granitic gneiss. In the investigation area, the radionuclide concentration in water supply, river and water well is low, and hence the water source is safe.
UNSCEAR. United Nations Scientific Committee on the Effects of Atomic Radiation [R]. New York: Exposure from natural sources of radiation,United Nations, 2000.