Proposed method for studying radon exhalation

Natural radioactivity is responsible for approximately 80% of the average annual radiation dose received by human being. This is mainly due to natural radionuclides in the Earth's crust that are generally referred to as primordial radionuclides. Approximately 65% of the population is expected to receive annual doses between 1 and 3 mSv, 25% below 1 mSv, and 10% exceeding 3 mSv Given the importance of Rn gas for the annual effective dose received by the human being and acknowledging geological factors' role in Rn emanation and exhalation, the World Health Organization (WHO) recommends that member countries implement national mapping programs to assess the increasing risk of Rn exposure based on geological and geographical studies. Peake and Schumann (1993) state that the most common sources of radon in soil gases are granitic rocks and metamorphic rocks, black shales, phosphate rocks and some carbonate rocks. According to the authors, granitic rocks commonly concentrate uranium in specific minerals during their initial crystallization phase. Considerable research has been presented on the gas transport process in the crust. In fractured rock, radium decay is the main source of radon. radon transport can understood that most radon in buildings is generated by radium decay in nearby soil and rock. Radon then migrates through soil pores by gas-phase diffusion and advection to the interfacial region between the soil and the building. Radon enters buildings primarily by advective transport of air through openings in the substructural shell, including cracks and deliberate penetration. Andrews and Wood [1972] and Bossus [1984] computed the escape probability for radon atoms generated within the recoil range of the surface of a spherical particle and obtained 23.5 and 25%, respectively. Porosity of a material allows radon to diffuse through it. Atmospheric ²²²Rn originates mainly from the decay of ²²⁶Ra atoms that are located in and on the surfaces of mineral grains in the uranium ore. The main objective of the study was to test the methodology for different grain sizes of a granite rock. (author)