钍样品放射性平衡判断方法

Determination method of radioactivity balance of thorium sample

天然样品中232Th的含量或活度通常可采用γ能谱法测量其子体212Pb来计算,其测定准确度取决于232Th系列的放射性是否平衡。然而,很多实际样品中232Th系列并不一定处于平衡状态,这就使得γ能谱法测定此类样品具有测定结果偏离真值的风险。通过研究总α放射性比活度和各个γ核素放射性比活度的理论关系,来判断样品钍系列是否处于放射性平衡状态,并通过硫酸浸泡打破天然平衡体系,实验验证了该判断方法的可行性。

The content or activity of 232Th in natural samples can be calculated by measuring its daughter 212Pb withγ-ray spectrometry.The accuracy of measurement depends on whether the radioactivity of 232Th series is balanced.However,the 232Th series in many practical samples are not always in equilibrium,which makes the 212Pb determination of such samples by gamma spectrometry with the risk of deviation from the true value.In this paper,the theoretical relationship between the totalαspecific activity and the specific activity of eachγnuclide was studied to determine whether the thorium series of samples are in the state of radioactive equilibrium or not.Then the natural equilibrium system can be broken with sulfuric acid soakin.the feasibility of the judgement method was verified by experiments.