风化壳淋积型稀土矿中^(138)La原位γ能谱法最小可探测活度的计算  

Calculation of the Minimum Detectable Activity of La in Weathered Crust Elution-deposited Rare Earth Ores with In-site γ Spectrometer

作　　者：李蔚成 赵剑锟 刘义保[1] 杨波 魏强林 邢义强 LI Wei-cheng;ZHAO Jian-kun;LIU Yi-bao;YANG Bo;WEI Qiang-lin;XING Yi-qiang(School of Nuclear Science and Engineering,East China University of Technology t Nanchang 330013,China;The College of Nuclear Technology and Automation Engineering,Chengdu University of Technology,Chengdu 610059,China;Fundamental Science on Radioactive Geology and Exploration Technology Laboratory,East China University of Technology,Nanchang 330013,China)

机构地区：[1]东华理工大学核科学与工程学院,江西南昌330013 [2]成都理工大学核技术与自动化工程学院,四川成都610059 [3]东华理工大学放射性地质与勘探技术国防重点学科实验室,江西南昌330013

出　　处：《稀土》2021年第4期10-16,共7页Chinese Rare Earths

基　　金：国家重大仪器专项(2017YFF0106503);国家自然科学地区基金项目(11965001);江西省教育厅科研项目(GJJ170479);放射性地质与勘探技术国防重点学科实验室开放基金项目(RGET1912)。

摘　　要：镧在赣南稀土矿中含量十分丰富,其中^(138)La作为镧的主要同位素,衰变过程中释放0.788 MeV(发射比0.344)和1.44 MeV(发射比0.656)的伽马射线。本文通过理论计算与蒙卡模拟相结合的方法建立一套针对^(138)La的现场伽马能谱测量方法。首先,利用数学理论计算得到探测器探测距离的最佳位置(距地0cm)和可探测范围(?60×20 cm)。其次,根据赣南地区七个典型稀土矿的U,Th,40K比活度数据,采用蒙特卡洛模拟获得U系,Th系,40K的天然放射性本底"秒谱"。最后,计算了^(138)La的最小可探测活度,在1000 s测量时间下^(138)La的最小可探测活度可降低至在29.88 Bq/kg~121.69 Bq/kg。Rare earth lanthanum is very rich in southern Jiangxi rare earth ore. ^(138)La is the main radioactive isotope of lanthanum, which released 0.788 MeV(34.4%) and 1.44 MeV(65.6%) gamma rays during the decay process. In this article, an in-site detection method of La gamma spectrum was designed by theoretical calculation and Monte Carlo simulation. Firstly, a mathematical model of in-site detection was built to obtain the best detecting distance(0 cm from the ground) and detectable range(φ60×20 cm). Then, based on the U, Th and 40K specific activity data of seven typical rare earth mines in Jiangxi Province, the "peak efficiency" characteristics of natural gamma radiation were constructed by Monte Carlo simulation method.Finally, under the measurement time of 1000 s, the minimum detectable activity of ^(138)La was calculated to be 29.88 Bq/kg~121.69 Bq/kg.

关 键 词：稀土 ^(138)La 最小可探测活度 蒙特卡洛模拟 

分 类 号：X837[环境科学与工程—环境工程] R144[医药卫生—公共卫生与预防医学]