The International Atomic Energy Agency (IAEA) this week led a team of international experts in conducting sampling of Advanced Liquid Processing System (ALPS) treated water that had been diluted with seawater ahead of its discharge into the sea at the Fukushima Daiichi Nuclear Power Station (FDNPS) in the sixth mission carried out under the IAEA’s Additional Measures.
The IAEA and Japan agreed in September 2024 to implement the Additional Measures to enhance transparency of the ALPS treated water release and expand international participation in IAEA-led sampling missions. These measures allow third parties to conduct hands-on, independent checks of water concentration levels to confirm that the discharge of ALPS-treated water— initiated by Tokyo Electric Power Company Holdings (TEPCO) in August 2023—continues to meet international safety standards. TEPCO intends to discharge the treated water in a series of batches over the coming decades.
The IAEA began implementing these Additional Measures in October 2024. In February 2025, IAEA Director General Rafael Mariano Grossi presided over the Additional Measures to collect seawater samples in the vicinity of FDNPS.
During this week’s mission – from 4 to 5 December – the international experts from the People’s Republic of China, the Republic of Korea, the Russian Federation and Switzerland, alongside IAEA staff, conducted hands-on sampling of water from the discharge vertical shaft/ seawater pipe header. This part of the discharge facilities is where the ALPS-treated water is diluted with seawater before being released through a one-kilometre-long tunnel into the sea.
The samples were taken from the 17th batch of water, the discharge of which commenced yesterday. The IAEA confirmed that the tritium concentration in the batch is far below Japan’s operational limit.
Samples collected during the mission will be analysed by participating laboratories including: the China Institute for Radiation Protection, the Korea Institute for Nuclear Safety, the Institute for Problems of Environmental Monitoring of the Research and Production Association “Typhoon” in Russia, the Spiez Laboratory in Switzerland, the IAEA Fukushima laboratory and TEPCO in Japan.
All international laboratories involved are members of the IAEA’s Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA) network, selected for their demonstrated expertise and analytical excellence.
