Radiometric analysis and implementation of a new hazard index (IBRA) for Brazilian construction materials

Abstract

A set of 8 groups with 239 samples of a total of 49 types of different materials representative of the most commonly used construction materials in low-income dwellings in Brazil was collected from construction materials stores in the state of Rio de Janeiro (Brazil). The radiometric analysis of the NORMs radionuclides (²²⁶Ra, ²³⁵U, ²³²Th, and ⁴⁰K) in the samples was performed by gamma radiation spectrometry. The results of the specific concentrations of the gamma-ray spectra in the area under investigation using a High Purity Germanium (HPGe) detector with 30% efficiency were 26.0 ± 1.1, 25.3 ± 0.4, and 223 ± 14 Bq kg⁻¹ for ²²⁶Ra, ²³²Th, and ⁴⁰K, respectively. The average values are below the world limit of 50, 50, and 500 Bq kg-1 for ²²⁶Ra, ²³²Th, and ⁴⁰K, respectively. Only the granite, marble, and quartz samples showed measurable values of ²³⁵U, and it was below 5 Bq kg⁻¹. The hazard index for gamma radiation due to the use of Brazilian construction materials (I_BRA) was formulated. The average I_BRA value was 0.23 ± 0.01. The highest average values above 1 in the I_BRA were found in sand, bricks, and gravel, due to the high background of the locations where their raw materials were extracted. Most samples presented an effective dose below the permissible limit value of 1.0 mSv y⁻¹. In general, the materials analyzed in this study can be used in dwelling construction without great radiological risk to the health of the inhabitants.