The discharge of treated water from Japan’s Fukushima Daiichi NPP is proceeding in line with international safety standards, the International Atomic Energy Agency (IAEA) Task Force confirmed in its third report since the water discharge began in August 2023.
Contaminated water, used to cool the melted reactor cores in the aftermath of the 2011 nuclear disaster at Fukushima, is stored in around 1,000 huge tanks at the plant containing more than 1.3m tonnes and total storage capacity has been reached. The contaminated cooling water and groundwater is treated by the Advanced Liquid Processing System (ALPS), which removes most of the radioactive contamination, with the exception of tritium.
The treated water is then stored in tanks before being diluted with seawater to one-fortieth of the concentration permitted under Japanese safety standards before being released one kilometre off the power plant. As a result, tritium levels fall below national regulations. The water will be discharged in batches over a period of approximately 30 years.
During its mission to Japan in December 2024, the IAEA Task Force assessed the technical and regulatory aspects of the ALPS-treated water discharge. This included an on-site visit to the Fukushima facility to directly observe the equipment and infrastructure installed by plant operator Tokyo Electric Power Company (Tepco), the for the water discharge. The report also summarised the Task Force’s discussions with the Nuclear Regulation Authority (NRA), Japan’s Ministry of Foreign Affairs (MOFA) and Ministry of Economy, Trade and Industry (METI).
The Task Force report reaffirmed the findings of the IAEA’s comprehensive safety review, stating that its overall conclusions remain consistent with those from its first and second missions conducted after the discharge began. It emphasised that NRA has maintained a comprehensive inspection plan, including onsite monitoring to ensure the safety of the water that is discharged. It also confirmed that the equipment and facilities are operating in accordance with relevant international safety standards.
The IAEA Comprehensive Report on the Safety Review of the ALPS-Treated Water at the Fukushima Daiichi Nuclear Power Station released in July 2023 before the first discharge, found Japan’s approach to discharging the treated water to be consistent with international safety standards. It concluded that the discharges as planned would have a negligible radiological impact to people and the environment. The Task Force has carried out eight missions as part of the safety review since the beginning of IAEA’s multi-year review that began two years before the water discharge.
This latest report also reviewed IAEA’s ongoing independent verification of Japan’s monitoring programmes, as well as onsite sampling and analysis conducted by IAEA experts at Fukushima since July 2023, when Director General Rafael Mariano Grossi established an IAEA office at the site. IAEA’s onsite laboratory has analysed the first 11 water discharges, confirming that the tritium concentration in each batch remains well below Japan’s operational limit consistent with international safety standards.
The Task Force noted the importance of IAEA’s ongoing corroboration activities and IAEA onsite independent sampling and analyses in providing a comprehensive, transparent and independent verification of the accuracy and reliability of the data reported by Tepco and the Government of Japan.
The IAEA has also released reports on two interlaboratory comparisons (ILCs) for determining radionuclides in ALPS-treated water and in marine environmental samples collected from near to Fukushima NPP, part of the Agency’s comprehensive monitoring and assessment efforts. ILCs involve multiple laboratories independently analysing samples, then reporting their results to IAEA for evaluation to assess their reliability and accuracy.
One report presents the findings from an ILC based on samples collected during a mission in October 2023 when the IAEA, with experts from third-party laboratories, observed Japan’s collection and pretreatment of samples of seawater, sediment, fish and seaweed from coastal and offshore locations and a fish market close to the NPP. Laboratories in Canada, China and South Korea, as well as IAEA’s laboratories in Austria and Monaco, analysed the samples and reported the results to IAEA for intercomparison.
The IAEA report confirms that Japan’s methods for sampling follow the appropriate methodological standards and that Japanese laboratories have reported accurate results that demonstrate a high degree of proficiency. IAEA notes that these findings provide confidence in Japan’s capability for conducting reliable and high-quality monitoring related to the discharge of ALPS treated water.
The second ILC report corroborates Japan’s source monitoring of ALPS treated water from the eighth batch before discharge in August 2024. Water sampled from the tanks was analysed by laboratories in China, South Korea, Switzerland and the US, as well as at IAEA laboratories. Following assessment of the results, IAEA said the findings provide confidence in Tepco’s capability for conducting reliable and high-quality source monitoring.
IAEA has also released a report confirming that Tepco is accurately monitoring the internal radiation exposure of workers handling ALPS-treated water. The report presents the findings from ILCs organised by IAEA last year, which corroborated results from IAEA, French and Japanese laboratories. The findings highlight that Tepco has demonstrated a high level of accuracy in their measurements and strong technical competence. A report focusing on external radiation exposure monitoring was published in November 2024.
All reports, as well as additional information such as frequently asked questions and a timeline of activities, can be found on the IAEA’s Fukushima Daiichi ALPS Treated Water Discharge webpage.
