Assessment of natural radioactivity in soil samples collected around the thermal power plant area of Cuddalore district, Tamil Nadu.

This study investigates the natural radioactivity levels of ²³⁸U, ²³²Th, and ⁴⁰K in soil samples using a NaI (Tl) gamma-ray spectrometer. The primary objective was to determine the activity levels of radionuclides such as ²³⁸U, ²³²Th, and ⁴⁰K in soil samples and to assess the related radiological risk. Based on these measurements, several radiological parameters, including radium equivalent activity (Ra_eq), outdoor absorbed dose rate (ADR_out), annual effective dose equivalent (AEDE_out), excess lifetime cancer risk (ELCR_out), external hazard indices (H_ex), and annual gonadal dose equivalent (AGDE), were calculated. Additionally, the effective radiation dose to specific body organs (D_organ) was estimated to evaluate the potential biological impact of external gamma radiation exposure. The results indicate that the activity level of ²³⁸U slightly exceeds the world recommended limit of (35 Bq kg^-1), while the calculated radiological variables such as ADR_out (101 ± 13 nGy h^-1), AEDE_out (0.12 ± 0.02 mSv y^-1), ELCR_out (0.43 ± 0.08), and AGDE (366 ± 48 µSv y^-1) were slightly higher than the internationally recommended safety limits. Multivariate statistical analysis was performed, helping to identify potential sources and interrelationships among the measured radionuclides and radiological variables.