IAEA Conducts Marine Sampling in Japan to Review Fukushima Water Discharges

An International Atomic Energy Agency (IAEA) team is in Japan from 2 to 12 September 2025 to conduct marine sampling near the Fukushima Daiichi Nuclear Power Station (FDNPS). The mission is part of the Agency’s long-term safety review of the ALPS-treated water discharges, following the controversial release of water that began in August 2023.

Mission Objectives

The IAEA scientists, alongside international experts, are observing the collection of seawater, marine sediment, fish, and seaweed samples from the coastal waters around Fukushima. They are also sampling at a local fish market and monitoring the preparation and packaging of samples before delivery to accredited laboratories.

The samples will help verify whether the Advanced Liquid Processing System (ALPS)-treated water discharges—approved by the IAEA in July 2023—remain safe for humans and the environment.

Background: ALPS-Treated Water Discharge

The IAEA Comprehensive Report on the Safety Review of the ALPS-Treated Water, released on 4 July 2023, found that Japan’s plan to discharge the water was consistent with international safety standards. The report concluded that the radiological impact of the discharges would be negligible.

On 24 August 2023, Tokyo Electric Power Company Holdings (TEPCO), operator of the FDNPS, began releasing the treated water into the Pacific Ocean. Since then, the IAEA has maintained an office at the site, conducting regular independent monitoring of water batches. The Agency has confirmed that tritium concentrations in all 14 batches discharged so far were far below operational limits.

Independent International Verification

This week’s mission includes experts from:

• France’s Authority for Nuclear Safety and Radiation Protection (ASNR)

• Korea Institute of Nuclear Safety

• Spiez Laboratory, Switzerland

All three are members of the IAEA’s Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA) network, ensuring independent corroboration of Japan’s monitoring data.

The IAEA conducts interlaboratory comparisons (ILCs) in which identical samples are analyzed by multiple laboratories, including:

• IAEA’s own laboratories in Monaco and Vienna

• ALMERA laboratories in France, Korea, and Switzerland

• Japanese institutions

The results will be compared for consistency, and any statistically significant differences will be closely examined.

Timeline for Results

Once samples are distributed and analyzed, findings will be compiled and evaluated. Due to the complexity of testing and international collaboration, the final results will be published in the second half of 2026.

The extended timeline reflects the need for:

• Sample homogenization and distribution to multiple laboratories.

• Rigorous radionuclide analysis using advanced methods.

• Cross-checking and validation of results.

Part of a Broader Monitoring Effort

This mission is part of the IAEA’s broader multi-year safety review of ALPS-treated water discharges. Previous ILCs have already assessed:

• TEPCO’s capacity to measure radionuclides in stored treated water.

• The accuracy of Japanese laboratories in testing seawater, sediment, fish, and seaweed.

An additional ILC focused on source monitoring of ALPS-treated water collected in July 2025 is also underway.

Assurance for Local and Global Communities

Since the 2011 Fukushima disaster, concerns have persisted over the safety of releasing treated water into the ocean, with environmental groups, neighboring countries, and local fishing communities expressing skepticism. The IAEA’s independent monitoring aims to build confidence in the safety of the discharges.

In addition to its current mission, the Agency will use collected samples for its long-standing marine monitoring quality assurance project initiated in 2014, further supporting the reliability of Japanese laboratory practices.

The IAEA stresses that independent, science-based monitoring is essential to ensuring transparency and accountability in managing Fukushima’s treated water. While early findings confirm that released water meets safety standards, the upcoming multi-laboratory analyses—expected in 2026—will provide further assurance to Japan, its neighbors, and the international community.