The hydrochemistry of groundwater from 47 wells in the Chungwon area, Korea was analyzed to examine the occurrence of natural radionuclides like uranium and radon. The range of Electrical Conductivity (EC) value in the study area was 67∼1,404 μS/cm. In addition to the high EC value, the content of cations and anions also tends to increase. Uranium concentrations ranged from ND～178 μg/L (median value, 0.8 μg/L) and radon concentrations ranged from 80～12,900 pCi/L (median value, 1,250 pCi/L). Uranium concentrations in one well, that is 2.8% of the samples, exceeded 30 μg/L, which is the Maximum Contaminant Level (MCL) proposed by the US Environmental Protection Agency (EPA), based on the chemical toxicity of uranium. Radon concentrations in three wells, that is 6% of the samples, and one well, that is 2.8% of the samples, exceeded 4,000 pCi/L (AMCL of the US EPA) and 8,100 pCi/L (Finland’s guideline level), respectively. Concentrations of uranium and radon related to geology of the study area show the highest values in the groundwater of the granite area. The uranium and radon contents in the groundwater were found to be low compared to those of other countries with similar geological settings. It is likely that the measured value was lower than the actual content due to the inflow of shallow groundwater by the lack of casing and grouting.

Abstract
 1. 서 론
 2. 연구방법
  2.1. 연구지역의 지질
  2.2. 시료채취 측정방법
 3. 결과 및 고찰
  3.1. 지하수의 수질특성
  3.2. 지하수의 우라늄과 라돈함량 분포 특징
  3.3. 방사성물질과 지질과의 상관관계
 4. 결 론
 REFERENCES

• 이병대(한국지질자원연구원 지질환경연구본부) | Byeongdae Lee (Geologic Environmental Division, Korea Institute of Geoscience and Mineral Resources) Corresponding author