The investigation of 137Cs and 90Sr background radiation levels in soil and plant around Tianwan NPP, China.

(137)Cs and (90)Sr background levels in soil and plant around Tianwan Nuclear Power Plant (NPP) are reported. Eighty-four soil samples and 44 plant samples were collected from March 2000 to April 2002. The samples were analyzed by gamma spectrometry and radiochemical separation procedure to quantify (137)Cs and (90)Sr radioactivities. The concentrations (Bqkg(-1) dry weight) have been observed in the range of 0.6-1.6 for (90)Sr and 1.4-6.9 for (137)Cs in soils, their average values are 1.0+/-0.3 and 4.6+/-1.6, respectively, which are relatively lower than the reported values in neighboring countries. The mean concentrations (in Bqkg(-1) fresh weight except for tea and grass which is expressed in Bqkg(-1) dry weight) of (137)Cs and (90)Sr are 0.1+/-0.03 and 7.7+/-4.1 in pine needle, 0.27+/-0.05 and 3.0+/-1.1 in tea, 0.65+/-0.19 and 2.1+/-0.3 in grass, 0.033+/-0.021 and 0.084+/-0.045 in wheat, 0.019+/-0.01 and 0.23+/-0.06 in China cabbage, and 0.009+/-0.007 and 0.024+/-0.084 in rice, respectively. The pine needle and tea can be regarded as indicator species for (90)Sr and (137)Cs. The soil-to-plant transfer factor (TF) values of (90)Sr and (137)Cs are, respectively, 0.022 and 0.031 for rice, 0.066 and 3.83 for China cabbage, 0.0088 and 0.089 for wheat, and 0.037 and 0.56 for grass.

Radioactivity concentrations in soils of the Xiazhuang granite area, China.

The natural radioactivity of soils at the Xiazhuang granite massif of Southern China has been studied. The radioactivities of 55 samples have been measured with a low-background HPGe detector. The radioactivity concentrations of (238)U and (40)K ranged from 40.2 to 442 and from 442 to 913 Bq/kg, respectively, while the radioactivity concentration of (232)Th varied only slightly. In order to evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity (Ra(eq)), the absorbed dose rate (D ), the annual effective dose rate and the external hazard index (H(ex)) have been calculated and compared with the internationally approved values. The study provides background radioactivity concentrations in a granite area, specifically, the area in the vicinity of a uranium mine in Southern China. The data can be used in exploring granite-type uranium deposits.