IAEA, Global Experts Sample Fukushima Water Under New Transparency Measures

The activity marks a pivotal moment under newly implemented “additional measures” designed to ensure robust monitoring of Japan’s process of discharging treated water from the plant into the Pacific Ocean.

In a significant step toward enhancing transparency and international oversight, the International Atomic Energy Agency (IAEA) and scientific experts from the People’s Republic of China, the Republic of Korea, the Russian Federation, and Switzerland carried out the first joint sampling mission of diluted Advanced Liquid Processing System (ALPS) treated water at Japan’s Fukushima Daiichi Nuclear Power Station (FDNPS). The activity marks a pivotal moment under newly implemented “additional measures” designed to ensure robust monitoring of Japan’s process of discharging treated water from the plant into the Pacific Ocean.

This mission, which took place today at the FDNPS site, involved collecting water samples from the discharge vertical shaft and seawater pipe header — key points where the ALPS-treated water is mixed with seawater before being released into the ocean through a one-kilometre-long undersea tunnel. The sample collection focused on the 12th batch of treated water since the discharge began in August 2023. Just last week, the IAEA independently verified that the concentration of tritium in this batch was significantly below Japan’s established operational limits.

This event represents the first on-site sampling by international experts under the newly expanded IAEA framework for environmental monitoring at Fukushima. These additional measures, agreed upon in September 2024 between the IAEA and the Japanese government, aim to bolster global trust and ensure that discharges remain in compliance with international safety standards. They are designed to allow third-party scientists to independently assess whether the water discharge meets safety criteria, both now and in the future.

Participating experts represented leading national institutions with advanced radiological analysis capabilities. These included:

• China Institute for Radiation Protection (China)

• Korean Institute for Nuclear Safety (Republic of Korea)

• Institute of Natural Monopolies Research (Russian Federation)

• Spiez Laboratory (Switzerland)

All of these institutions are active members of the IAEA’s Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA) network, a globally recognized group of laboratories selected for their technical excellence and analytical accuracy in radiological assessments.

The samples collected during the mission will undergo analysis at the IAEA Environmental Laboratories in Monaco, as well as at domestic Japanese facilities and the four participating national laboratories. This multilayered testing approach ensures cross-verification of results and upholds the scientific integrity of the findings.

This latest mission builds on a series of monitoring initiatives by the IAEA since Japan began its discharge process. It follows a February 2025 expedition in which IAEA Director General Rafael Mariano Grossi joined experts from several nations to conduct seawater sampling by boat near the FDNPS site. An earlier step in the additional measures was carried out in October 2024, when international experts participated in collecting seawater samples around the discharge area, setting the stage for today’s milestone.

The ALPS system, operated by Tokyo Electric Power Company (TEPCO), is designed to remove radionuclides from contaminated water, with the exception of tritium, a weakly radioactive isotope of hydrogen. Before discharge, the treated water is diluted with a large volume of seawater to reduce tritium levels far below safety thresholds recommended by international standards. The IAEA’s continued presence on the ground and its cooperation with international laboratories help ensure that this process remains safe, transparent, and in line with best practices.

The IAEA reiterated its commitment to maintaining an open and transparent process throughout the long-term water discharge operation, expected to span several decades. The organisation stressed that public communication, independent validation, and international collaboration are essential for building and maintaining trust with the Japanese public, neighbouring countries, and the global community.

As further sampling and analyses are conducted, results will be made publicly available, continuing the IAEA’s practice of full disclosure and technical reporting. This approach ensures that all stakeholders can access reliable scientific data regarding the environmental impact of the Fukushima water discharge.

The latest sampling marks an important step forward in international cooperation on nuclear safety, environmental protection, and post-accident management — reinforcing the shared global responsibility to monitor and verify complex decommissioning efforts.