UNATTACHED 212PB FRACTION IN THE WORKER’S BREATHING ZONE AT HIGH THORON CONCENTRATIONS

Classical aerosol physics predicts that it is impossible to observe noticeable values of the unattached fraction of decay products of thoron at typical concentrations of aerosol particles. The experimental data have shown that the unattached fraction of the thoron decay products in a monazite storage facility is in the range 0.3–0.6. This effect is caused by local increase in air exchange near the inlet of the sampling device at high 220Rn concentrations. It was found that a dynamic shift between the unattached and attached thoron decay products is also observed in the worker’s breathing zone at a high concentration of thoron. The 212Pb unattached fraction in worker’s breathing zone was ~0.4. It demonstrates that when evaluating inhalation exposure to the products of the decay of thoron, it is necessary to take into account the increase of the 212Pb unattached fraction in the worker’s breathing zone.

FSUE SRI IMM: Evolution of Devices for Radon Control and its DPR

Preparation and implementation of measures to reduce radiation doses to personnel of enterprises engaged in the extraction and processing of uranium-containing ores, and the population of the territories adjacent to uranium deposits, require an increase in the accuracy of estimates of absorbed and effective doses to the personnel of enterprises and the population with the inhalation of radon and its progeny. This can only be done by taking into account the contribution of the aerosol-unattached fraction of the radon decay progeny to the effective and absorbed radiation doses, which are evaluated on the basis of direct measurements. Alpha spectrometer SAT-03 – a means of measurement of the third generation, has been developed in the Research Institute of Industry and Maritime Medicine for these purposes. Widespread domestic radiometers of the previous generation (RAA-10, RRA-01M) do not have the technical capabilities to perform such studies.