Natural Isotopic Activity Ratios as Evidence of Migration and Leaching of Uranium in Egyptian Granitic Rocks

Ismaiel, Nahla A.; Frag, Eman Y.; Seif, W. M.; Mira, Hamed I.; Shabasy, Ahmed M.; Khattab, Mahmoud R.

doi:10.1088/1742-6596/2830/1/012022

Natural Isotopic Activity Ratios as Evidence of Migration and Leaching of Uranium in Egyptian Granitic Rocks

Document Type : Original Article

Authors

¹ Radiation Protection Department, Nuclear Power Plants Authority (NPPA), Cairo, Egypt.

² Chemistry Department, Faculty of Science, Cairo University, Giza 12613, Egypt.

³ Physics Department, Faculty of Science, Cairo University, Giza 12613, Egypt.

⁴ Geochemical Exploration Department, Nuclear Materials Authority, Cairo, Egypt.

⁵ Nuclear and Radiological Safety Research Centre (NRSRC), Egyptian Atomic Energy Authority (EAEA), Nasr City, Cairo 11762, Egypt.

10.1088/1742-6596/2830/1/012022

Abstract

Gamma-spectrometry was utilized to analyse radionuclides in granitic rocks from the El Eridiya area through radiometric measurements. The activity concentration of 238U ranges from 3493±83 to 5209±104 Bq kg-1, while for 234U and
its isotope (235U), it varies from 957±32 to 1012±34 Bq kg-1 and 153.0±4.5 to 256.0±5.5 Bq kg-1, respectively. However, for the isotopes 230Th and 232Th, the range is from 11217±254 to 16291±305 Bq kg-1 and 31.0±1.1 to 85.3±0.5 Bq kg-1, respectively. The activity concentration of 40K ranged from 67.9±1.6 to 109.0±2.1 Bq kg-1. The ratios of 234U/238U in the studied granitic rock samples vary from 0.21±0.01 to 0.54±0.03. Due to the current oxidising conditions, most of the rock samples show a higher presence of 234U compared to 238U, with 234U/238U activity ratios below one. Additionally, the activity ratios of 232Th/238U range from 0.006 to 0.019 in the granitic rock samples from the El Eridiya area. Figures 3 and 4 display uranium enrichment, with all samples showing 232Th/238U ratios below one for the earth's crust. Additionally, all samples showed 230Th/238U and 230Th/234U activity levels above one, suggesting preferential leaching of uranium in an oxygen-rich setting. Similarly, the 234U/238U and 230Th/238U activity ratios are below and above
one, indicating U-leaching and U-accumulation, respectively. Figure 3 and 4 show uranium enrichment, with all samples having 232Th/238U activity ratios below one for the earth's crust. There were benefits to uranium leaching in an environment with oxidation in all samples, with 230Th/238U and 230Th/234U activity ratios exceeding one. If the 234U/238U activity ratio is lower than one but the 230Th/238U activity ratio is higher than 1, it suggests U-leaching; if the 234U/238U activity ratio is greater than one and the 230Th/238U activity ratio is less than 1, it suggests U-accumulation.

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