Assessment of natural radionuclides and its radiological hazards from tiles made in Nigeria

The possibility of the phosphogypsum use in the production of brick: Radiological and structural characterization

In this paper, phosphogypsum (PG) with the content of ²²⁶Ra of about 500 Bq kg^-1 was used as a clay additive in mass ratios of (0-40) % and its influence on the radiological and mineralogical characteristics of the obtained brick samples was monitored. After sintering the samples at 1000 ℃, the formation of the mineral phase gehlenite was observed, and its share increased with the share of PG in the samples. The Monte Carlo method was used to determine the gamma dose rates, and consequently annual effective dose, for a standard room, with dimensions 4 × 5 × 2.8 m, whose walls were built of brick with PG. The obtained values were in the range (0.22-0.35) mSv y^-1. In addition, the active device RAD7 was used to determine the radon surface exhalation rates from the samples, which were found to be in the range (63-150) mBq m^-2 h^-1. The estimated indoor radon concentrations were found to be drastically lower than 100 Bq m^-3, leading to low radon inhalation doses. However, estimated annual effective doses from external gamma exposure were found not to be insignificant.

Investigation of natural environmental radioactivity concentration in soil of coastaline area of Ado-Odo/Ota Nigeria and its radiological implications

Natural radioactivity in coastaline area soil of Ado-Odo/Ota has been carried out to ascertain the presence of radionuclides using gamma-ray spectroscopy (HPGe detector). The result showed that U-238, Th-232 and K-40 ranged from 24 ± 7-49 ± 10; 67 ± 6-120 ± 9 and 88 ± 17-139 ± 20 Bqkg^-1 respectively. The radium equivalent for the samples ranged from 132.51 to 230.91 Bqkg^-1 with mean value of 185.89 Bqkg^-1. The mean value for the gamma dose rate for the soil samples was estimated to be 81.32 nGyh^-1. The estimated values of annual effective dose equivalent ranged from 0.61 to 1.07 mSv y^-1. The estimation of alpha index representative (Iα) ranged from 0.12 to 0.24 with mean value of 0.21 while the gamma representative index ranged between 0.465 and 0.810. The activity utilization index of the soil samples ranged from 1.09 to 1.89 with mean value of 1.53. The radiological implication in the study area has shown that the soil samples with gamma dose rate value of 89.99 nGyh^-1, 94.39 nGyh^-1, 97.40 nGyh^-1 and 101.04 nGyh^-1 respectively are higher than the recommended value of 80 nGyh^-1 and may pose health implication for long term exposure.

Comparative Study of Natural Radioactivity and Radiological Hazard Parameters of Various Imported Tiles Used for Decoration in Sudan

Various commercially imported ceramic materials used in the building of Sudanese dwellings were examined in order to determine their natural radioactivity and radiological hazard parameters. In this context, twenty-five different consignments were sampled and analyzed using (3″ × 3″) sodium iodide gamma spectrometry system NaI(Tl). The identified average activity concentrations of 238U, 232Th, and 40K were 183 ± 70, 51 ± 44, and 238 ± 77 Bq/kg dry-weights, respectively. A positive correlation between 238U and 232Th in the investigated samples was identified from the observed significant correlation (R2 = 0.8). Interestingly, a low Th/U ratio (~0.3) was recorded, which could be related to the systematic loss of thorium during the fabrication process. The measured activity concentrations for these radionuclides were comparable with the reported data obtained from similar materials used in other countries showing similarity in ceramic materials used in buildings. Five different radiation indices, such as the average radium equivalent (Raeq), the absorbed dose rate (D), the annual effective dose equivalent (AEDE), the external hazard index (Hex), and the radioactivity level index (lγ), which indicate hazardous radiation, were estimated from these measurements. The obtained results revealed average values of 274 ± 106 Bq/kg, 125 ± 48 nGy/h, 1.23 ± 0.48 mSv/y, 0.74 ± 0.29, and 0.94 ± 0.37, for Raeq, D, AEDE, Hex, and lγ, respectively. The mean values of Raeq and Hex were in good agreement with the international limits, while the means of D and lγ were higher than the universal values. Calculated AEDE in about 60% of the samples exceeded the universal limit of 1 mSv/y for the public exposure (maximum value of 2.16 mSv/y). The investigated parameters were in the same range for the majority of imported samples; however, they were slightly higher than the locally produced ceramic, highlighting the importance of monitoring imported materials for their radioactivity contents.

Radioactivity and radiological hazards from a kaolin mining field in Ifonyintedo, Nigeria

The concentrations of the radionuclides in the subsurface formation (soils and rocks) solely depend on their geological origin, which enables its variation from point to point on the Crust. Construction materials can possess elevated concentrations of radioactivity if their byproducts are mined from contaminated radionuclide sources. In this article, results of in situ measurements of radioactivity concentrations of ⁴⁰K, ²³²Th, and ²³⁸U as well as gamma doses and radiological hazards from kaolin mining field were presented and evaluated. Eleven stations were randomly occupied in order to cover the upper axis of a kaolin mining field in Ifonyintedo. The radiometric survey was achieved using Super-Spec (RS-125), equipment capable of measuring activity concentrations and gamma doses. For each location, measurements were taken four times, while its mean and standard deviation values were estimated for better accuracy. The overall mean activity concentrations (for ⁴⁰K, ²³²Th and ²³⁸U) and gamma dose were estimated as 93.9 Bq kg^-1, 65.1 Bq kg^-1, 38.2 Bq kg^-1, and 59.6 nGyh^-1 respectively. The estimated radiological hazards from the measured parameters showed that the overall mean concentrations of Radium Equivalent, External and Internal Hazards, Annual Effective Dose, Gamma and Alpha Indices, and Representative Level index are 138.5 Bq kg^-1, 0.37 0.48, 0.29 mSvyr^-1, 0.48, 0.19, and 0.97 respectively. By comparing the mean values of the activity concentrations and their radiological risks with the several world standards from the literature, kaolin deposits in Ifonyintedo are highly rich in thorium.