RESUMEN
The natural radioactivity in our living environment is mainly due to radionuclides of 40K, 232Th and 238U. We studied the distribution of these radionuclides in the sediment of different rivers and streams throughout the Kathmandu valley. The activity concentrations were determined by using digiBase NaI(TI) gamma-ray spectrometer, and further they were used to calculate radiological hazard indices to estimate the risk associated with the use of these sediments. The average activity concentrations for 40K, 232Th and 238U were found to be 378.54 ± 109.06, 45.95 ± 18.47 and 26.90 ± 9.61 Bq per kg, respectively. The average concentrations and calculated hazard indices have been compared with the respective reported activity concentration in different countries. This study reveals that there is no radiological threat using these local sediments as building materials and for other purposes.