Kannan V, Rajan M P, Iyenga M A R, Ramesh R
Health Physics Division, BARC, Kalpakkam, India.
Appl Radiat Isot. 2002 Jul;57(1):109-19. doi: 10.1016/s0969-8043(01)00262-7.
Pre-operational survey at Kalpakkam coast, indicated elevated gamma background radiation levels in the range of 100-4000 nGy h(-1) over the large tracts of the coastal sands due to the presence of pockets of monazite mineral in beach sands. In view of the prevalence of monazite, a systematic gamma spectrometric study of distribution of natural radionuclides in soil and beach sand samples collected from the terrestrial and coastal environment of Kalpakkam was performed and concentrations of primordial radionuclides such as 238U, 232Th and 40K and anthropogenic radionuclide 137Cs were determined. The concentrations of 238U, 232Th and 40K in soil samples were 5-71, 15-776 and 200-854 Bq kg(-1) dry, respectively. In beach sand samples, 238U, 232Th and 40K contents varied in the range of 36-258, 352-3872 and 324-405 Bq kg(-1) dry, respectively. The total absorbed gamma dose rate in air due to the presence of 238U, 232Th and 40K in Kalpakkam soil samples varied between 24 and 556 nGy h(-1) with a mean of 103 nGy h(-1). The contribution to the total absorbed gamma dose rate in air in the decreasing order was due to the presence of 232Th (76.4%), followed by 40K (16.9%) and 238U (6.7%) in Kalpakkam soils. However, in beach areas of Kalpakkam, the presence of 232Th in beach sand contributed maximum (94.0%) to the total absorbed gamma dose rate in air followed by 238U (4.7%) and minimum contribution was by 40K (1.3%). 137Cs in Kalpakkam soils ranged from < or = 1.0 to 2.8 Bq kg(-1) dry, which was 1-3 order of magnitude less than the concentration of primordial radionuclides in soil.
对卡尔帕卡姆海岸进行的运行前调查表明，由于海滩沙子中存在独居石矿囊，在大片沿海沙地中，伽马本底辐射水平升高，范围在100 - 4000纳戈瑞每小时（nGy h⁻¹）。鉴于独居石的普遍存在，对从卡尔帕卡姆陆地和沿海环境采集的土壤和海滩沙子样本中的天然放射性核素分布进行了系统的伽马能谱研究，并测定了原生放射性核素如²³⁸U、²³²Th和⁴⁰K以及人为放射性核素¹³⁷Cs的浓度。土壤样本中²³⁸U、²³²Th和⁴⁰K的浓度分别为5 - 71、15 - 776和200 - 854贝克勒尔每千克干重（Bq kg⁻¹）。在海滩沙子样本中，²³⁸U、²³²Th和⁴⁰K的含量分别在36 - 258、352 - 3872和324 - 405贝克勒尔每千克干重（Bq kg⁻¹）范围内变化。卡尔帕卡姆土壤样本中由于²³⁸U、²³²Th和⁴⁰K存在导致的空气中总吸收伽马剂量率在24至556纳戈瑞每小时（nGy h⁻¹）之间变化，平均值为103纳戈瑞每小时（nGy h⁻¹）。在卡尔帕卡姆土壤中，对空气中总吸收伽马剂量率贡献由高到低依次为²³²Th（76.4%），其次是⁴⁰K（16.9%）和²³⁸U（6.7%）。然而，在卡尔帕卡姆的海滩区域，海滩沙子中²³²Th对空气中总吸收伽马剂量率的贡献最大（94.0%），其次是²³⁸U（4.7%），⁴⁰K的贡献最小（1.3%）。卡尔帕卡姆土壤中¹³⁷Cs的含量范围为≤1.0至2.8贝克勒尔每千克干重（Bq kg⁻¹），比土壤中原生放射性核素的浓度低1至3个数量级。
