Radon Exhalation From Granitic Rocks

Abstract

Naturally occurring radionuclides such as radon (222Rn), its decay products and other elements from the radioactive series of uranium (238U and 235U) and thorium (232Th) are an important source of human exposure to natural radioactivity. The worldwide evaluation of health radiobiological effects and risks from population exposure to natural radionuclides is a growing concern. About 50% of personal radiation annual dose is related to radionuclides such as radon (222Rn), thoron (220Rn), radium (226Ra), thorium (232Th) and potassium (40K), which are present in modern materials commonly used in construction of dwellings and buildings. The radioactivity of marbles and granites is of big concern since under certain conditions the radioactivity levels of these materials can be hazardous to the population and require the implementation of mitigation procedures. Present survey of the 222Rn and 220Rn activity concentration liberated in the air was performed using commercialized Brazilian granite rocks at national market as well as exported to other countries. The 222Rn and 220Rn measurements were performed using the AlphaGUARD instant monitor and RAD7 detector, respectively. This study was performed at the Applied Nuclear Physics Laboratory of the Federal University of Technology – Paraná (UTFPR). Obtained results of radon concentration activity in air exhaled studied samples of granites varied from 3±1 Bq/m3 to 2087±19 Bq/m3, which shows that some samples of granitic rocks represent rather elevated health risk the population.