IAEA finds TEPCO's ALPS treated water monitoring accurate in fourth comparison
Samples were collected in July 2025 from tanks at Fukushima Daiichi holding the 15th batch of ALPS treated water discharged into the sea.
Key facts
- Reported detection limits under 1% of regulatory limits for all radionuclides in TEPCO's source term
- Independent labs in China, France, the Republic of Korea and Switzerland joined IAEA labs in Austria and Monaco
- IAEA has maintained a continuous presence at Fukushima Daiichi since before discharge began in August 2023
- Sampling mission October 5 to 17, 2026 to collect seawater, sediment and biota near the plant
The IAEA published its fourth interlaboratory comparison on the determination of radionuclides in ALPS treated water on October 5, finding that TEPCO reported accurate results and demonstrated a high degree of proficiency in monitoring the water at Fukushima Daiichi.
The comparison checked TEPCO's analytical results against those from IAEA laboratories in Austria and Monaco and expert laboratories in China, France, the Republic of Korea and Switzerland, all members of the IAEA's ALMERA network. The IAEA said TEPCO's sample collection procedures followed the methodological standards required to obtain representative samples, and that the analytical methods it selected for different radionuclides were appropriate and fit for purpose.
Reported detection limits were less than one percent of the respective regulatory limits for all radionuclides in TEPCO's source term, the report found. The samples were collected in July 2025 from tanks at Fukushima Daiichi holding the 15th batch of ALPS treated water discharged into the sea.
The IAEA has maintained a continuous presence at the site since before the discharge began in August 2023. From October 5 to 17, 2026, it will collect and pre-treat seawater, sediment and biota samples around the plant for interlaboratory comparisons, accompanied by experts from China's Third Institute of Oceanography, the Korea Institute of Nuclear Safety and Switzerland's Spiez Laboratory.
