Solid-state alpha-track detectors using cellulose nitrate films were used to measure the radon exhalation rates from building materials. The radon flux emitted from the surface of the building material was measured by placing an inverted cup on the top of the building material. Cellulose nitrate film was placed within the cup. Tracks due to alpha particles from radon that migrate from the building material into the air space in the cup were registered on the cellulose nitrate film. The films were etched in a solution consisting of 10(-3) m3 2.5 N NaOH solution. A spark counter or microscope was used to record the tracks appearing on the cellulose nitrate film. The average exhalation rate of radon was obtained by means of a simple mathematical approach that can be used to estimate the maximum possible radon concentration in a closed room due to building materials alone. Infiltration and ventilation effects were excluded in this work. This new technique and simple approach can be used to establish the data base for average radon exhalation rates from all available building materials and walls or floors. The maximum indoor radon concentration can be estimated from the measured average radon exhalation rate by using this simplified model.

Natural radiation in houses built with black schist slabs located at an altitude of 1,000 m in the mountainous southern part of Taiwan were investigated by studying the naturally occurring radionuclides present in the black schist. Both indoor and outdoor radon concentrations were monitored. The cosmic-ray contribution to the dose received by the inhabitants was also estimated. Gamma-ray spectroscopy was performed for radionuclide analyses. In situ measurements were carried out using a survey meter coupled to a sodium iodide detector. Cellulose nitrate films, ZnS (Ag) scintillation cells, and alpha spectroscopy were used to study radon and radon daughters. Radiation doses due to all natural sources were calculated and compared with that incurred in common concrete dwellings at lower altitudes.

Naturally occurring radon and thoron progeny are the most interfering nuclides in the aerosol monitoring system. The high background and fluctuation of natural radioactivity on the filter can cause an error message to the aerosol monitor. A theoretical model was applied in the simulation of radon and thoron progeny behavior in the environment and on the filter. Results show that even a small amount of airborne nuclides on the filter could be discriminated by using the beta:alpha activity ratio instead of gross beta or alpha counting. This method can increase the sensitivity and reliability of real-time aerosol monitoring.