Detection of 210Po on filter papers 16 years after use for the collection of short-lived radon progeny in a room

Abstract

Radon gas was allowed to accumulate in its radium source and then injected into a 36 m 3 test room, resulting in an initial radon concentration of 15 kBq m –3. Filter papers were used to collect the short-lived radon progeny and thus to measure the Potential Alpha Energy Concentration (PAEC) in-situ in the year 1984 at different times and conditions according to the experimental design. The radon progeny collected on the filter papers were studied as a function of aerosol particle concentration ranging from 10 2–10 5 particles cm –3 in three different experiments. The highest aerosol particle concentration was generated by indoor cigarette smoking. Those filters were stored after the experiment, and were used after 16 years to study the activity of the radon long-lived alpha emitter progeny, 210Po (T 1/2=138 days). This isotope is separated from the short-lived progeny by 210Pb beta emitter with 22.3 years half-life. After 16 years’ storage of these filters, each filter paper was sandwiched and wrapped between two CR-39 nuclear track detectors, to put the detectors in contact with the surfaces of different filters, for 337 days. Correlation between the PAEC measured using filter papers in the year 1984 and the activity of long-lived alpha emitter 210Po on the same filter papers measured in the year 2000 were studied. The results of the 210Po activity showed a very good correlation of 0.92 with the PAEC 16 years ago. The results also depict that the PAEC and 210Po activity in indoor air increased with the increase of aerosol particle concentration, which shows the attachment of short-lived radon progeny with the aerosol particles. The experiment proves that indoor cigarette smoking is a major source of aerosol particles carrying radon progeny and, thus, indoor cigarette smoking is an additional source of internal radiation hazard to the occupants whether smoker or non-smoker.