Assessment of the impact of Tianwan Nuclear Power Plant on the adjacent marine ecosystem

Based on the monitoring data of 137Cs and 90Sr in Tian Bay in 2005–2023, the impacts of the operation of Tianwan Nuclear Power Plant on the marine ecosystem were assessed. The 137Cs and 90Sr activity concentrations in the seawater and sediment varied within the background ranges. The radiation dose rates derived from 137Cs and 90Sr for the marine organisms ranged from 2.4 × 10−5 to 2.2 × 10−4 nGy/h, it was far below the most conservative screening dose rate (10 μGy/h). The committed effective dose for humans was 0.070–0.094 μSv, 1/1500th of the world's mean annual effective dose (0.12 mSv) from ingesting food containing uranium and thorium series nuclides. Radiation risk assessment showed no radiation risk for the long-term discharge of nuclear wastes in the future. Overall, the long-term normal operation of TNPPs has almost no radiation impact on the adjacent marine ecosystem. •137Cs and 90Sr fluctuated within the background range of Tian Bay.•Dose rate from 137Cs and 90Sr to marine biota was far below the threshold (10 μGy/h).•No radiation effect on the marine ecosystem of Tian Bay from radionuclides•No radiation risk for long-term discharge of low-level radioactive waste to Tian Bay