Japan’s Tokyo Electric Power Company (TEPCO), the operator of the Fukushima Daiichi Nuclear Power Station (NPS), has demonstrated its capabilities for accurate and precise measurements of the radionuclides present in the treated water stored on site, according to the International Atomic Energy Agency’s (IAEA’s) latest report covering its independent sampling and analysis work. This is part of its ongoing review to assess the safety related aspects of Japan’s plan to release the treated water from the Fukushima Daiichi NPS into the sea. In line with relevant IAEA international safety standards, Tepco is required to monitor the characteristics and activity of the treated water in order to accurately evaluate public exposure that will result from the discharge and to comply with its national regulatory authorisation.

The IAEA observed and facilitated the collection of the treated water samples analysed in the report from tanks at the Fukushima Daiichi NPS in March 2022. This water was taken from the first batch of Advanced Liquid Processing System (ALPS) treated water expected to be discharged into the sea. The IAEA is independently checking the types and amounts of radionuclides contained in the ALPS treated water. This corroboration effort falls under one of the three components in the IAEA’s multi-annual safety review which also includes assessments of the technical plans and of regulatory activities and processes related to the treated water discharge.

The samples were corroborated based on an interlaboratory comparison (ILC) which involves different laboratories separately testing and analysing samples and then comparing results and procedures to determine their reliability and accuracy. The samples taken for the report were analysed by TEPCO; by the IAEA in its laboratories in Monaco, and in Seibersdorf and Vienna, Austria; and in third-party laboratories in France, the Republic of Korea, Switzerland and the United States. All these are members of the network of Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA). Additional samples have been taken from other batches of water and are undergoing a similar analysis as part of the wider review process.

“This report and the analytical results that it contains are an important milestone in the IAEA’s safety review. The data demonstrates TEPCO’s analytical performance through a transparent and rigorous scientific process,” said Gustavo Caruso, Director and Coordinator for the ALPS Safety Review, IAEA Department of Nuclear Safety & Security and Chair of the Task Force.

In particular, the report found that:

  • TEPCO has demonstrated a high level of accuracy in their measurements and technical competence.
  • TEPCO's sample collection procedures follow the appropriate methodological standards required to obtain representative samples.
  • The selected analytical methods utilised by TEPCO for different radionuclides were appropriate and fit for purpose.
  • Neither the IAEA nor the participating third-party laboratories detected any additional radionuclides at significant levels.

Additional reports on corroboration will cover baseline environmental samples (e.g., seawater, fish) from the surrounding environment of Fukushima Daiichi NPS and an assessment of the capabilities of monitoring services involved in the assessment of internal and external radiation exposure of workers at Fukushima Daiichi NPS.

The IAEA’s comprehensive report on its review is being prepared and will be issued in due course.

Meanwhile, South Korean nuclear safety experts who visited Fukushima said detailed analysis was needed to verify Japan's plan to release tonnes of contaminated water from it into the sea. Japan plans to release more than 1m tonnes of contaminated water that was mainly used to cool the reactors into the sea by around this summer, triggering protests, especially in fishing communities.

"Given our closest location, we are reviewing whether Japan has an appropriate discharge plan from a scientific and technological standpoint," Yoo Guk-hee, Chairman of the Nuclear Safety & Security Commission, who recently led a South Korean delegation on a site visit. Yoo said there had been progress in checking facilities and securing samples and documents but further work was needed to reach any conclusion about the water's safety. "Additional detailed analysis and checks are required," he said.

The 21-member South Korean team, during a six-day trip had focused on water purification, transport and release equipment, as well as sampling and analysis facilities. The visit came days after President Yoon Suk Yeol and Japanese Prime Minister Fumio Kishida held a summit in Seoul this month amid a thaw in relations following years of tension between the neighbours.

Image: Aerial view of the water storage tanks at the Fukushima Daiichi nuclear power plant (courtesy of TEPCO)