Radioactivity of organically bound tritium and carbon-14 in sea food from waters near nuclear power plant and committed effective dose of exposed people in Zhejiang province, 2020

  Objective   To examine the radioactivity of organically bound tritium (OBT) and carbon-14 (¹⁴C) in seafood from waters near nuclear power plant and to estimate annual committed effective dose of people exposed to the sea food in Zhejiang province for providing background data for assessing environmental and biological impacts of potential pollution due to the discharge of nuclear wastewater from foreign nuclear power plant.

  Methods  The survey was conducted at two monitoring sites in Haiyan and Sanmen county close to two nuclear power plants and a control site in Dinghai district of Zhoushan city in Zhejiang province during April – October 2020. Fish, shrimp and seashell samples were collected to determine radioactivity of OBT and ¹⁴C in edible parts of the samples. The committed effective dose of people potentially exposed to the sea food was estimated based on the detection results and estimated consumption amount of the sea food.

  Results  For the samples collected at the sites in Haiyan county, Sanmen county, and the control district, the radioactivity (in Bq/per kilogram fresh edible sea food) of OBT ranged from < method detection limit (MDL) to 0.24, < MDL to 0.42, and < MDL to 0.34 and those of ¹⁴C ranged from 3.53 to 12.20, 11.55 to 20.34, and 8.35 to 19.59, respectively; the estimated annual radioactive dose (in Bq) for an individual due to the exposure to OBT in the sea food consumed were 4.79, 8.61, and 11.56 and those due to the exposure to ¹⁴C were 242.19, 397.55, and 529.63; the corresponding committed effective dose (in mSv/per year) for an individual exposed to both OBT and ¹⁴C in the sea food were 1.41 × 10 ^{– 4}, 2.31 × 10 ^{– 4}, and 3.08 × 10 ^{– 4}, accounting for 0.06%, 0.09%, and 0.12% of personal annual radioactive dose constraint value, respectively.

  Conclusion  The radioactive activity of OBT and ¹⁴C in three types of sea food from waters in areas near nuclear power plant were not significantly different from that in the sea food from waters in control area and at a background level in Zhejiang province in 2020. The annual radioactive exposure to OBT and ¹⁴C and the committed effective radioactive dose for individuals with consumption of the sea food were relatively low, so as the radioactive dose burden for local population.