Assessment of radiation risk and radon exhalation rate for granite used in the construction industry

The influence of building material structure on radon emanation

In this work, the radon emanation coefficients for selected building materials that are most often used in Serbia for covering floor surfaces (concrete, concrete screed, granite, glazed ceramic tiles, marble, roofing tile, and terrazzo tile) were determined, and the influence of the material structure on their values. The concentration of²²⁶Ra activity in the samples was determined using the gamma spectrometry method. Radon emanation was measured with the RAD7 device. The porosity of the samples was tested using mercury intrusion porosimetry and water absorption methods, and the structural analysis was performed using x-ray diffraction analysis and x-ray fluorescence analysis. The measured values of²²⁶Ra activity concentrations were in the range (4.93-298) Bq kg^-1, and the estimated values of the radon emanation coefficients were in the range (0.55-6.05) %. The obtained results indicate that the chemical and mineralogical composition, method of production, and the²²⁶Ra activity concentration have an influence on the emanation of radon from the material. No significant correlation was found between the radon emanation coefficient and the open porosity of the material, most likely due to the inhomogeneous presence of pores of different dimensions in the materials. It was established that the total value of the emanation coefficient depends on the emanation coefficient for pores ⩽100μm in size.

Health Hazards Assessment and Geochemistry of ElSibai-Abu ElTiyur Granites, Central Eastern Desert, Egypt

In this paper, a thorough radio- and chem-ecological evaluation of ElSibai-Abu ElTiyur granites located within Egypt’s crystalline basement rocks was conducted for risk and dose assessments. Twenty granitic samples from the study area’s various lithological units were analyzed using high-resolution γ-ray spectrometry to determine the natural radioisotopes (U-238, Th-232, and K-40) concentrations. The average concentrations of U-238, Th-232, and K-40 were 38.72, 38.23, and 860.71 Bq/kg, respectively, exceeding the GAV (global average value) documented by UNSCEAR (Scientific Committee on the Effects of Atomic Radiation, Vienna, Austria). The radiological parameters and indices judging the usage of ElSibai-Abu ElTiyur granites in homes were computed. The obtained results showed that ElSibai-Abu ElTiyur granites are safe to be used by inhabitants as superficial building materials, as per the globally accepted values and the recommended safety limits approved by UNSEAR, WHO (World Health Organization, Geneva, Switzerland), ICRP (International Commission on Radiological Protection, Ottawa, ON, Canada), and EC (European Commission, Luxembourg). Further, the samples were subjected to ICP-MS (inductively coupled plasma mass spectrometry) analysis for quantifying radionuclide variations with chemical composition. Geochemically based on the ICP-MS results, the studied granites proved to be highly evolved A-type granites. They span the metaluminous to peralkaline fields. The REE patterns are characterized by the enrichment of the light rare earths (LREE) over the heavy ones (HREE) where (La/Yb)n = 5.2, (Gd/Yb)n = 1.63 with pronounced negative Eu-anomalies (Eu/Eu*)n = 0.49. The albite granite exhibits the highest concentrations of Ga, Nb, Ta, U, and Y, and REE (Gd, Dy, Ho, Yb) than the Na-metasomatic granites. Finally, the obtained data serve as a valuable future database for finding out the compatibility of the geochemical data with the natural radioactivity levels of granites.

Estimation of absorbed gamma dose rate from granite by Monte Carlo simulation approach

Apart from the continuous exposure of humans to background ionising radiation, an increased level of radiation may also originate from the use of building materials with an enhanced level of radioactivity. Thus, it is necessary to examine the content of radionuclides present in building materials, as well as the corresponding dose which may be received by residents from these materials. In this paper, particular attention was dedicated to finding the absorbed dose rate and annual effective dose caused by the presence of naturally occurring radioisotopes ²²⁶Ra, ²³²Th, and ⁴⁰K in granite, a widely used building material, by means of Monte Carlo simulations. In addition, the obtained dose rate simulation results were compared with values estimated from commonly used simple equations, relating to the dose rate emitted by granite plates, covering the interior of a standard room. In the simulation, a room was constructed with standard dimensions (4 m × 5 m × 2.8 m), and with floor and walls covered with 3 cm thick granite. A water cylinder (approximate mass 65 kg) was positioned in the center of the room, representing a human body. The emission of the most intense gamma rays from ²²⁶Ra and ²³²Th progenies, as well as from ⁴⁰K, emanating from the granite matrix, was simulated. The number of generated photons in each simulation (typically it was an order of magnitude of ~10⁶) precisely represented actual activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in granite samples. All processes playing a role in the interactions of gamma photons with the granite matrix itself, the outer concrete shell, the air within the room, and the water cylinder, were taken into account by GEANT4 simulation software, after which the spectra of deposited energy inside of the water cylinder were obtained. Based on the deposited energy, the absorbed dose rate and annual effective dose were calculated for 6 analysed granite samples, each with different ²²⁶Ra, ²³²Th, and ⁴⁰K contents. Furthermore, the effect of the position of the water cylinder in the simulated room on the absorbed dose rate was considered, as well as the distribution of the deposited energy within the water cylinder. The absorbed dose rates, and consequently annual effective dose, obtained in the simulations were found to be 30%-40% higher than the values obtained from using a standard formula.