Exploring Radioactivity in Common Building Materials

Many stones used in building materials can contain varying amounts of naturally occurring radioactive elements that emit radiation. Uranium-238, thorium-232 and potassium-40 are among the naturally occurring radioactive elements commonly found in stones used in building materials that can decay into the radioactive gas radon. Radon-222 forms by the alpha decay of radium-226, both of which are daughter nuclides in the U-238 decay chain. Radon is an odorless, colorless gas that can lead to lung cancer when inhaled in high doses. Granite is a naturally occurring stone whose durability and decorative appearance makes it a popular building material in homes and buildings. The amount of radiation emitted by granite or other stones and soil depends on the concentration of the unstable radionuclides (such as U-238, Th-232 and K-40) present in the materials, which can vary based on the geographical location where the stone was obtained. In this project samples of granite distributed commercially in the United States, China, Qatar and Guyana were obtained and surveyed. A Geiger counter was used to measure radioactivity. Preliminary results from the U.S.A samples indicated that the Caravelas Gold sample exhibited the highest radioactivity, averaging 312 cpm/kg from separate measurements, when background radiation ranged from 28-40 cpm. A Teledyne Flir Identifinder was also used to determine specific radioactive isotope present in each sample. Among the U.S.A samples, only the Caravelas Gold sample had a detectable amount of Ra-226. Trends in radioactivity obtained from the various samples surveyed will be presented. This project is based upon work supported by the NNSA Minority Serving Institutions Partnership Program under Award No. NA0004162. Any opinions, findings, and conclusions or recommendations expressed in this project are those of the authors and do not necessarily reflect the views of the DOE, NNSA, or the U.S. Government.