Baseline Radiological Survey for Radiation Protection from Kushma to Galeshwor along the Kaligandaki River, Nepal

Background: The Kaligandaki River from Kushma to Galeshwor is considered a high natural background radiation area, requiring baseline assessment of naturally occurring radionuclides for radiation protection.Materials and Methods: A portable gamma-ray spectrometer (PGIS-2) equipped with a NaI(Tl) scintillator detector was employed. Radiological hazard parameters, including radium equivalent activity, absorbed gamma dose rates in air, annual effective dose rate, external hazard index, and internal hazard index, were determined.Results and Discussion: The mean activities of radionuclides ²³⁸U, ²³²Th, and ⁴⁰K, were found to exceed global average values. Radium equivalent activity ranged from 141.48 Bq·kg⁻¹ to 313.24 Bq·kg⁻¹, with a mean value 204.91 Bq·kg⁻¹ for the Kushma–Galeshwor region. The annual effective dose rates were 0.12 mSv· yr⁻¹ and 0.47 mSv· yr⁻¹ for outdoors and indoors, respectively.Conclusion: Although these values exceed global averages, they remain within established safety limits. The findings highlight the importance of continuous monitoring to ensure environmental and public safety in regions with naturally occurring radioactive materials. Therefore, from a radiation protection perspective, the region is considered safe.