The IAEA Published a Report on its Fourth Review Mission of Safety Related Aspects of the Discharge of ALPS Treated Water into the Sea After the Start of the Discharge

1．Summary

From May 26 to 30, 2025, IAEA officials and international experts (from Argentina, Canada, China, the Republic of Korea, Russia, the United States and Vietnam) visited Japan to conduct IAEA’s review mission of safety aspects of the discharge of ALPS treated water into the sea. This is the fourth review mission after the start of the discharge into the sea.
This fourth report after the start of the discharge into the sea presents conclusions based on the IAEA review mission conducted in May, this year. The report highlights that, as in the first through third reports after the start of the discharge, the Task Force did not identify anything that is inconsistent with the requirements in the relevant international safety standards.

2．Key Points of the Report

(1) Viewpoints of Review

The report focuses on reviewing and understanding Japan's various monitoring programmes being carried out for ALPS treated water, and confirms whether or not  they are in compliance with relevant international safety standards through discussions between the IAEA Task Force and the Japanese government (Nuclear Regulation Authority (NRA), Ministry of the Environment (MoE), the Fisheries Agency of Japan(FAJ), Ministry of Economy, Trade and Industry (METI), and Ministry of Foreign Affairs (MOFA)), the Fukushima Prefecture (FP), and TEPCO, and through site visits to TEPCO’s Fukushima Daiichi Nuclear Power Station. 

(2) Main Review Results

The IAEA’s overall conclusions agree with those highlighted in the previous three missions after the start of the discharge:

• The Task Force did not identify anything that is inconsistent with the requirements in the relevant international safety standards. Therefore, the IAEA can reaffirm the fundamental conclusions of its safety review as outlined in the IAEA Comprehensive Report.
• The Task Force noted that the monitoring programmes carried out for the ALPS treated water are consistent with the relevant international safety standards and guidance. The programmes are well described and implemented, and results are consistent with the conclusions of the Radiological Environmental Impact Assessment (REIA) which states the discharges of ALPS treated water pose negligible risk to the public and environment.
• The Task Force highlighted that the NRA has maintained regulatory oversight of the ALPS treated water through its own confirmatory monitoring programmes and its onsite presence to maintain safety oversight of the discharge of ALPS treated water. 
• The Task Force confirmed that the equipment and facilities are installed and operated in a manner that is consistent with the Implementation Plan and the relevant international safety standards.
• The Task Force noted the importance of the IAEA’s ongoing corroboration activities and the IAEA’s onsite independent testing and analysis. This oversight continues to provide comprehensive, transparent and independent verification of the accuracy and reliability of the data reported by TEPCO and the Government of Japan.

3. Response to the IAEA Report

Through the IAEA review, the Government of Japan will continue to take measures in accordance with international safety standards and take all possible measures to ensure the safety of the discharge of ALPS treated water. We will continue to maintain close coordination with the IAEA in sharing information with the international community in a highly transparent manner and work on fostering better understanding of the safety of the discharge of ALPS treated water both domestically and internationally.

Related Links

• The IAEA Press Release (September 12, 2025 (local time in Vienna, Austria))
• The IAEA Report (Report 4: Fourth Review Mission to Japan after the Start of Advanced Liquid Processing System Treated Water Discharge (May 2025))
• The IAEA Conducted the Fourth Review Mission on the Safety of the Discharge of ALPS Treated Water into the sea since the Start of the Discharge into the Sea (May 30, 2025)
• The IAEA Press Release (March 24, 2025 (local time in Vienna, Austria))
• The IAEA Report (Report 3: Third Review Mission to Japan after the Start of ALPS Treated Water Discharge (December 2024))
• The IAEA Conducted a Review Mission on the Safety of the Discharge of ALPS Treated Water (December 13, 2024)
• The IAEA Published a Report on Its Second Review Mission of Safety Aspects of Handling of ALPS Treated Water at Fukushima Daiichi Nuclear Power Station since the Start of the Discharge in April 2024 (July 18, 2024)
• The IAEA Published a Report on Its Second Review Mission of Safety Aspects of Handling of ALPS Treated Water at Fukushima Daiichi Nuclear Power Station since the Start of the Discharge in October 2023 (January 30, 2024)
• Publication of the IAEA Comprehensive Report on the Safety Review of the ALPS Treated Water at TEPCO’s Fukushima Daiichi nuclear Power Station (FDNPS) (July 4, 2023)
• Let's get to know and understand about ALPS treated water. [Ministry of Economy, Trade and Industry]
• IAEA Website about ALPS treated water

Related website

• ALPS Treated Water

Division in Charge

Nuclear Accident Response Office, Agency for Natural Resources and Energy