【摘要】 论述了运用区域化探数据预测地-空界面天然放射性水平的基本原理和方法技术。运用成都市区1∶50 000土壤化探数据中铀、钍、钾的含量数据,成功预测了成都市区的放射性水平,并具有如下特征:(1)成都市区天然环境放射性核素40K,238U和232Th的比活度分别为300~900 Bq/kg,15~70 Bq/kg,25~80 Bq/kg;其外照射指数为0.35~0.7,内照射指数为0.17~0.31,二者都在国家建筑材料放射性核素限量标准控制值的范围内。(2)成都市区空气中吸收剂量率分布呈正态分布,其均值为88.5 nGy/h,均方差为9.7 nGy/h;γ外照射年剂量当量为:0.43~0.67 mSv,均属于正常范围。(3)由于双流-成都-德阳隐伏断裂带的影响,使得断裂带附近外照射指数和空气吸收剂量率相对偏高,并且造成成都市区西部外照射指数和空气吸收剂量率高于东部,其外照射指数比东部约高0.05,空气吸收剂量率约高10 nGy/h。与常规的核辐射测量仪器实地测量的方法相比较,该文提出的评价方法更加节省了人力、物力和时间。更多还原

【Abstract】 The evaluation of natural radioactivity on the interface of ground and atmosphere has become an important task of environment evaluation for human being.This paper describes a new evaluation method of natural radioactivity.It uses the data of geochemical prospecting obtained in the early geological investigation to predict the natural radioactivity on the ground-air interface,instead of measuring in the field with gamma radiation instruments.The principle and some key techniques of the method have been discussed in the paper.Based on the concentration of U,Th and K in soils obtained from 1∶250000 geochemical prospecting in Chengdu,some characters of natural radioactivity in Chengdu area can be conclued as following: 1)The specific activities of 40K,238U and 232Th in soils are 300～900 Bq/kg,15～70 Bq/kg and 25～80 Bq/kg,respectively;the external and internal exposure indexes are 0.35～0.7 and 0.17～0.31,respectively,which are less than the national limit of radionuclides in building materials.2) The frequency of gamma ray absorbed dose rate in Chengdu area submits to Gauss’s distribution, the statistical average is 88.5 nGy/h and the standard deviation is 9.7 nGy/h;the annual dose equvalent of gamma ray field on humans is about 0.43～0.0.67 mSv.3) It is significant that the fault zone named Shuangliu-Chengdu-Deyang Fault across Chendu area influences the natual radioactivity distribution.The external exposure index and gamma ray absorbed dose rate in the area to the west of the fault are about 0.05 and 10 nGy/h,respectively,higher than that to the east of the fault,and the relative highest values are on the fault zone.更多还原