北京市环境天然贯穿辐射水平调查研究

INVESTIGATION OF ENVIRONMENTAL NATURAL PENETRATING RADIATION LEVEL IN BEIJING

本文报道了北京市环境天然贯穿辐射水平的调查方法和结果。北京市市区以1×1 km 网格布点83个,郊区县以10×10 km 网格布点173个,共布设网格点256个,各类加密点131个。调查结果表明:(1)北京市原野γ辐射剂量率按面积、人口和网格点加权均值分别为56.4、50.1和56.2nGy·h^(-1)。西部和北部山区较高,东南部平原区较低;(2)道路γ辐射剂量率按网格点均值为49.3nGy·h^(-1);(3)室内γ辐射剂量率按人口和网格点加权均值分别为77.1和83.5 nGy·h^(-1);(4)宇宙射线电离成份(不包括中子)所致空气吸收剂量率按测点和按人口加权的均值,室内分别为29.0和27.5 nGy·h^(-1),室外分别为32.3和30.8 nGy·h^(-1);(5)天然贯穿辐射剂量率(不包括中子成分)按测点和按人口加权的均值,室内分别为112.8和104.5 nGy·h^(-1),室外分别为88.7和81.3 nGy·h^(-1);(6)天然γ辐射、宇宙射线和天然贯穿辐射所致的北京市人均年有效剂量当量分别为0.43、0.25和0.68 mSv,全市集体年有效剂量当量分别为4.0、2.3和6.3×10~3人·Sv。

This paper reports the methods and results of investigation of environmental naturalpenetrating radiation level in Beijing.There were 83 measurement points selected,which were locatedat the vertexes of 1×1 km square meshes and uniformly distributed over the urban district.173 netgrid measuring points seleted with grid spacing of 10×10 km and uniformly distributed over thesuburban district.Another 131 more densely distributed points were added over some special areas.The results show that:(1)The point-weighted,area-weighted and population-weighted average valueof natural y radiation dose rate over field is 56.2,56.4 and 50.1 nGy·h^(-1)respectively.The γradiation dose rate is higher in west and north area than in southeast area.(2)The poiont-weightedaverage value of natural γ radiation dose rate over roads was 49.3 nGy·h^(-1).(3)The point-weighted and population-weighted average value of natural γ radiation dose inside buildings was 83.5and 77.1 nGy·h^(-1)respectively.(4)The weighted average of air absorbed dose rate from theionizing components of cosmic rays (except for neutron) over point number and population wasrespectively 29.0 and 27. 5 nGy·h^(-1)indoors,and 32.3 and 30.8 nGy·h^(-1)outdoors.(5)Thepoint and population-weighted means of natural penetrating radiation dose rate(the contribution fromneutron is not included)are 112.8 and 104.5 nGy·h^(-1)indoors,respectively;88.7 and 81.3 nGy·h^(-1)outdoors, respectively.(6)The annual effective dose equivalent per capital groin natural γradiation,cosmic ray and natural penetrating radiation was 0.43,0.25 and 0.68 mSv respectively,and the annual collective effective dose equivalent was 4.0,2.3 and 6.3×10~3 man·Sv,respectively.