RADON EXHALATION RATE FROM VARIOUS BUILDING-MATERIALS

Solid-state alpha-track detectors using cellulose nitrate films were u sed to measure the radon exhalation rates from building materials. The radon flux emitted from the surface of the building material was meas ured by placing an inverted cup on the top of the building material. C ellulose nitrate film was placed within the cup. Tracks due to alpha p articles from radon that migrate from the building material into the a ir 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 so lution. A spark counter or microscope was used to record the tracks ap pearing 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 clo sed room due to building materials alone. Infiltration and ventilation effects were excluded in this work. This new technique and simple app roach can be used to establish the data base for average radon exhalat ion rates from all available building materials and walls or floors. T he maximum indoor radon concentration can be estimated from the measur ed average radon exhalation rate by using this simplified model.