The method of Pb-212 measurements in air with the application of the LSC technique

This paper describes a method enabling the measurement of the potential alpha energy concentration (PAEC) of thoron decay products based on the determined concentration of lead ²¹²Pb (T_1/2 = 10.64 h) in the air [Lever et al., 2003]. A liquid scintillation spectrometer was used to determine the concentration of the ²¹²Pb isotope, and the sample was taken by pumping air through a filter where thoron decay products were stored. This method can be classified as integrating because the sample takes several hours, and the measurement results in one value for the entire sampling period. Measurements were carried out in laboratory conditions, in a climatic chamber where a constant supply of thoron was maintained, and in environmental conditions, in the basement of the family house and outdoors. Sampling took from 12 to 48 h. This article presents the preliminary results of the study. The obtained results were in the range of 170–195 Bq/m³ in the case of laboratory measurements and from 0.04 to 0.79 Bq/m³ in the case of environmental measurements. Based on the obtained results, the potential alpha energy concentration (PAEC) was calculated. The application of the low-level LS spectrometer allows for the achievement of a lower limit of detection (LLD) at level 0.04–0.05 Bq/m³, while the use of the portable LS spectrometer allows for the measurement of deficient ²¹²Pb concentrations in the range of 0.4–0.5 Bq/m³. The obtained results confirm that the method is suitable for determining the concentration of ²¹²Pb and, consequently, assessing exposure to thoron progeny.