科研之友
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摘要
Effective radium concentration ECRa, product of radium concentration and radon emanation, is the source term for radon release into the pore space of rocks and the environment. To measure ECRa, we have conducted, over a period of three years, more than 5500 radon-222 accumulation experiments in the laboratory with scintillation flasks, and about 700 with integrating solid state nuclear track detectors, leading to experimental values of ECRa for more than 1570 rock and soil samples. Through detailed systematic checks and intercomparison between various repeated experiments, the experimental uncertainty has been assessed, and ranges from 30% (1 sigma) for ECRa values smaller than 0.2 Bq kg(-1) to about 8-10% for ECRa values larger than 50 Bq kg(-1). The detection limit, defined as the 90% probability for obtaining a non-zero experimental ECRa value at 68% confidence level, depends on the mass of the sample with respect to the volume of the accumulation volume, and typically varies between 0.04 and 0.09 Bq kg(-1). To measure ECRa, from large numbers of samples with sufficient accuracy and uncertainty for our purpose, i.e. for the most natural objects encountered in the environment, the accumulation method with scintillation flask emerged as particularly useful and robust. Properties of ECRa and interpretations inferred from this large data set are presented in the companion paper.
- 出版日期2012-11
