IAEA confirms consistency of six-nation lab analyses of Fukushima seawater
Measured concentrations support the IAEA's 2023 finding that the discharges as planned would have a negligible radiological impact.
Key facts
- Seawater analyzed for tritium, strontium-90 and caesium-137; fish for caesium-137
- Surface seawater collected September 9, 2025; fish selected the following day
- TEPCO began discharging ALPS-treated water into the sea in August 2023
- Additional Measures launched October 2024 to broaden international participation and transparency
- All participating laboratories are members of the IAEA's ALMERA network
The IAEA published a report on October 28 that found independent analyses of marine samples collected near the Fukushima Daiichi Nuclear Power Station consistent with Japanese monitoring data. The samples were taken under the agency’s Additional Measures for the discharge of Advanced Liquid Processing System (ALPS)-treated water into the sea.
Surface seawater was collected on September 9, 2025, and fish the following day. Laboratories in Japan, China, the Republic of Korea, New Zealand, the Russian Federation and Switzerland, plus the IAEA’s Marine Environment Laboratories in Monaco, analyzed the seawater for tritium, strontium-90 and cesium-137 and the fish for cesium-137. The IAEA said the results were almost uniformly comparable and consistent with the Japanese monitoring data examined in the exercise.
The IAEA said the measured radionuclide concentrations support the conclusion of its 2023 Comprehensive Report that the discharges as planned would have a negligible radiological impact on people and the environment. Tokyo Electric Power Company Holdings (TEPCO), the plant operator, began discharging the water in August 2023, and the IAEA said the discharge remains subject to its ongoing safety reviews. The Additional Measures began in October 2024.
