Long Term Tritiated Water (ALPS-Treated Water) Exposure to Flounders and Analysis of Tritium Behavior Between Seawater and Flounder OBT

The Fukushima Daiichi Nuclear Power Plant accident generated more than 1E6 m3 of radiation-contaminated coolant water. In 2023, the Tokyo Electric Power Company (TEPCO) began the ocean release of coolant water containing tritium as tritiated water. Most of the radioactive materials except tritium were removed from the coolant water before release. The tritium release rate is up to 2.2E13 Bq/year. To prevent a negative impact on marine industries, TEPCO conducted a fish-rearing demonstration. Flounders (Paralichthys olivaceus) were reared in seawater containing 1.3 kBq/L tritium for approximately 2.5 years. The time-dependent concentration of organically bound tritium (OBT) in flounders was measured. The OBT concentration reached 18% of the tritium concentration in the rearing water and effectively reached the steady state after 2 years of exposure.