某核设施周围土壤中^(137)Cs放射性水平及所致居民外照射剂量评价

Evaluation of ^(137)Cs radioactivity level and the induced resident external exposure dose in soils surrounding a nuclear facility

^(137)Cs是核设施环境监测中重点关注的人工放射性核素。对2012—2021年某核设施周围土壤中^(137)Cs放射性水平进行了统计分析,与同类核设施进行了对比,建立了一套针对土壤中^(137)Cs所致居民外照射剂量的本底扣除方法,估算了该核设施周围土壤中^(137)Cs所致居民外照射剂量。结果表明:2012—2021年期间该核设施周围土壤样品中^(137)Cs的活度浓度平均值呈现出先下降后回升的趋势,近10年平均值1.81 Bq/kg,略高于同类核设施。从监测点位来看,^(137)Cs活度浓度平均值较高的6个点位中有4个分布在该核设施周围2 km半径内。该核设施周围土壤样品中的^(137)Cs所致居民年均外照射有效剂量为1.32μSv,仅为核设施公众年剂量目标值的0.5%。

^(137)Cs is an artificial radionuclide that has been paid special attention in environmental monitoring of nuclear facilities.In this paper,the ^(137)Cs radioactivity level in soils around a nuclear facility was statistically analyzed,and was compared with similar nuclear facilities from 2012 to 2021.The background deduction method was established for the external radiation dose caused by ^(137)Cs in soils,and the resident external radiation dose caused by ^(137)Cs in soils around the nuclear facility was estimated.The results showed that the activity concentration of ^(137)Cs in soil samples around the nuclear facility decreased first and then increased from 2012 to 2021,and the average activity concentration of 1.81 Bq/kg in recent ten years was slightly higher than that of similar nuclear facilities.From the point of view of monitoring locations,four of the six locations with the highest average ^(137)Cs activity concentration are distributed within a 2 km radius of the nuclear facility.The annual effective dose caused by ^(137)Cs from soil samples around the nuclear facility was 1.24μSv,which was only 0.5%of the target annual dose for the public specified for the nuclear facility.