Determination of radioactivity levels in water and sediment samples of the karasu and kabali rivers before the nuclear power plants in Sinop

This study aims to determine the background levels of radioisotopes 3H, 226Ra, 232Th, 40K and 137Cs in sediment and river water samples to be taken from two important rivers of Sinop before the nuclear power plant to be established in Sinop and to compare the determined levels with the limit values recommended by national and international organizations. In this context, both water and sediment samples were taken at 2 km intervals from the Karasu (80 km) and Kabalı (51.3 km) rivers in July, when there is the least rainfall and December, when there is the most precipitation. A total of 236 samples were taken each month, including 59 sediment samples and 59 river water samples. The coordinates of the sampled points were determined with the Magellan Explorist 510 GPS. Concentrations of 226Ra, 232Th, 40K, and 137Cs in the collected sediment and river water samples were measured using a High Purity Germanium Detector (HPGe) and tritium concentrations in river water samples were measured using a Liquid Scintillation Counter (LSC). In sediment samples taken from the Karasu River in December and July, the activity concentrations of 226Ra, 232Th, 137Cs, and 40K were between 3.08 – 29.40 Bq/kg, 2.95 – 19.10 Bq/kg, 0.35 – 61.13 Bq/kg and 54.83 – 495.02 Bq/kg, respectively. In sediment samples taken from the Kabalı river in December and July, the activity concentrations of 226Ra, 232Th, 137Cs, and 40K were between 5.79 – 25.65 Bq/kg, 3.35 – 19.55 Bq/kg, 0.97 – 7.23 Bq/kg and 141.66 – 446.77 Bq/kg, respectively. Average tritium activity concentrations in river water samples taken in December and July were 2.79 ± 0.52 Bq/L (23.65 ± 4.48 TU) and 1.75 ± 0.51 Bq/L (14.86 ± 4.36 TU) for the Karasu River and they were 2.37 ± 0.48 Bq/L (20.10 ± 4.08 TU) and 1.97 ± 0.46 Bq/L (16.67 ± 3.91 TU) for the Kabalı River. Radium equivalent activity (Raeq), external hazard index (Hex), absorbed dose rate (D), annual effective dose equivalent (AEDE) values were calculated and compared with the average values recommended by international organizations.