Radon-thoron exhalation and emanation determinations from mylonitic rock samples collected in north Abu Rusheid, Egypt

Mylonitic rocks in north Abu Rusheid, Egypt, contain naturally occurring radioactive materials (NORMs), making them potential sources of indoor radon (Rn) and thoron (Tn) exposure when used as building materials. Furthermore, they pose occupational exposure risks for miners. Rn mass exhalation rate (RnEX), Tn mass exhalation rate (TnEX), Rn emanation fraction (RnEM), and Tn emanation fraction (TnEM) were evaluated simultaneously in 27 mylonitic rock samples collected from three trenches (TCHA, TCHB, and TCHC) in the area. The powder sandwich technique has been carried out using a RAD7 detector to assess RnEX and TnEX. Additionally, gamma spectroscopy was used to evaluate RnEM and TnEM parameters. The RnEX and TnEX values varied from 0.10 to 1.13 and 83 to 5757 Bq kg⁻¹ h⁻¹, respectively, while the RnEM and TnEM values ranged from 0.055 to 0.182 and 0.017 to 0.078, respectively. The activity concentrations of ²²⁶Ra and ²³²Th varied from 127 to 1524 and 96 to 2420 Bq kg⁻¹, respectively, and the mean values exceeded the worldwide average values of 33 and 45 Bq kg⁻¹, respectively. Positive correlations between ²²⁶Ra and RnEX, and ²³²Th and TnEX were observed among the trenches. However, no systematic relations were identified between ²²⁶Ra and RnEM, ²³²Th and TnEM, or ²²⁶Ra and ²³²Th, which could be attributed to geological factors. The findings of this study highlighted the potential radiation hazards associated with mylonitic rock use in construction and mining, emphasizing the need for radioprotection measures.