Document Type : Research Paper

Authors

• ABOLFAZL SOLTANI ¹
• A. Moradi ²

¹ Asociate Prof., Faculty of Civil Engineering, Shahid Rajaee Teacher Training Uni., Tehran, Iran.

² M.Sc. of Civil, Faculty of Civil Engineering, Shahid Rajaee Teacher Training Uni., Tehran, Iran.

Abstract

The purpose of this paper is to determine the natural radioactivity indices of some Iranian granitites used in dwellings and to prevent the natural environmental hazards towards the sustainable development. A total of 62 samples were taken from 13 plutons of Iran; all were microscopically and isotopically studied in detail. The concentration of ²²⁶Ra, ²³²Th and ⁴⁰K in granitic samples were obtained by mass spectrometer in Arak and Tabriz universities. Microscopic observations and systematic data analyses are consistent and reveal the presence of radioactive minerals (e.g. zircon, apatite and titanite) particularly for samples rich in radioactive elements concentration. The average activities of the measured radionuclides varied up to 128 Bq kg^-1 for ²²⁶Ra, up to 118.6 Bq kg^-1 for ²³²Th, and up to 1385.46 Bq kg^-1 for ⁴⁰K, with mean values of 60.39, 78.47, and 884.72 Bq kg^-1, respectively. These values are higher than the standard values given for granites worldwide. To assess the radiation hazards associated with granite samples, average radium equivalent activity (240.72 Bq kg^-1), outdoor and indoor external hazard indices (0.65012, 0.325061), internal hazard index (0.81334), annual effective dose rate (0.13759 mSv/yr), excess life cancer risk (0.48155 mSv/yr.), and gamma radiation index (0.88856) were calculated. The average hazard indices of Iranian granites are smaller than the permitted limit given by UNSCEAR for public purposes, however there is some radiological risk from the usage of samples studied as internal decorative and ornamental building materials in dwellings. Due to the higher radiological hazard indices in granites of Birgand, Kordestan, Zanjan, Azerbayjan and Takab, certain caution is required when using these granites in private locations. In particular, these rocks are not authorized to be used as construction materials for hospitals, dormitories, educational spaces, kindergartens, jails and decorative. Application of standard recommendations of this research reduces the radioactive disease and helps the sustainable development aims (economic, society and environment), fundamentally.

Graphical Abstract

Keywords

• Granitic rocks
• Radioactivity
• Argon
• Thorium
• Potassium
• Building Materials