Determination of exhalation rates through measurements of alpha and beta radiation with the aid of liquid scintillation counter

Radon is a natural radioactive element in the gaseous form. It is a decay product of radium, which is present in all rocks and building materials. Radon escapes from them via diffusion and convection. The effect of radon releasing from solid materials to the pore air is called emanation. The parameters that characterise quantitatively this effect are the emanation coefficient and/or exhalation rate. The emanation coefficient η, expressed as percentage, is defined as a ratio of a number of radon atoms released from grains to the air in the pores to the entire number of radon atoms, produced by the decay of radium in an investigated sample. For many years the geologists have been exploiting the emanation effect for the purposes of the radioactive deposit prospecting and of general geology survey [10]. In the radiological protection, the exhalation rate can be used for the evaluation of the radon risk [9]. The exhalation rate is defined as an exhaled radon activity per mass or surface unit of the material sample and per unit of time. Determination of the radon concentration in air can be done with the help of various methods and devices: the Lucas cells, track detectors, electroscope detectors, activated charcoal detectors etc. Theoretical bases of enumerated methods can be found in papers describing radon measurements [3, 5, 11]. All of these methods are relative, which means that they use a reference method in order to be calibrated. Every calibration is valid for a certain range of values. In nature, radon concentrations vary in very broad range from several Bq/m in air upon the sea to the several hundreds kBq/m in soil gas in the vicinity of uranium deposits. In this paper, a method for measuring the radon content in an emanation chamber with the help of a liquid scintillation counter is presented. This method may be applied for a very wide range of radon concentrations and requires neither calibration nor reference methods. Determination of exhalation rates through measurements of alpha and beta radiation with the aid of liquid scintillation counter Nguyen Dinh Chau, Edward Chruściel