The discharge of treated water from Japan's Fukushima Daiichi NPP is progressing in accordance with the Implementation Plan approved by Japan’s Nuclear Regulation Authority (NRA), the Task Force set up by the International Atomic Energy Agency (IAEA) has confirmed.

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. The first discharge began in August 2023. The IAEA’s independent on-site analysis has confirmed that the tritium concentration in all five batches released to date is far below the operational limit of 1500 becquerels per litre.

The IAEA Task Force has now completed its second four-day mission to Japan since the start of the water releases. Its aim is to assess whether the approach taken by plant owner Tokyo Electric Power Company (Tepco) and the Government of Japan to discharge ALPS treated water is consistent with international safety standards.

The IAEA Task Force includes external experts from 11 countries – Argentina, Australia, Canada, China, France, the Marshall Islands, South Korea, Russia, the UK, the USA and Viet Nam as well as IAEA experts. It has conducted seven ALPS-related missions to Japan since February 2022. During its recent mission, the team visited facilities used for discharging the ALPS treated water. Accompanied by Tepco staff, the Task Force observed the tanks holding the water prepared for discharge, the transfer pumps building driving the water through the discharge system, the emergency isolation valves, the seawater pipe header diluting the water with seawater and the vertical shaft from where the diluted treated water travels to the sea.

The Task Force also examined the radiation monitors and flow rate detectors feeding live data to the IAEA’s dedicated real time monitoring page. It also engaged in technical discussions with Tepco with reference to available source and environmental monitoring data and operational experience gathered during the first five discharges. The Task Force also met with Japan’s Ministry of Economy, Trade & Industry and NRA.

In the IAEA Comprehensive Report on the Safety Review of the ALPS-Treated Water at the Fukushima Daiichi Nuclear Power Station that was released prior to the discharge, the Task Force provided several topics that it would review during the discharge of ALPS treated water. The main outcomes from the Task Force’s mission this week will be summarized in a report to be made publicly available later this year. The report on the First Review Mission to Japan after the Start of ALPS Treated Water Discharge (October 2023) is available online.

The IAEA’s independent, Comprehensive Report issued on 4 July 2023 found Japan’s approach to discharging the treated water is consistent with international safety standards and the results of the radiological environmental impact assessment performed by Tepco show that the release as planned would have a negligible radiological impact to people and the environment.

Gustavo Caruso, Chair of the Task Force, said, “The Task Force reviewed the consistency of activities before and during the operation of the ALPS treated water discharges with the relevant international safety standards. The independent and science-based work of the IAEA and the Task Force will continue throughout the process, as we are focused on the ongoing and long-term activities.”

IAEA Director General Rafael Mariano Grossi established an IAEA office at the NPP in July 2023 and signed an agreement with Japan in September 2023 that outlines the IAEA’s comprehensive and continuous safety review at the site and at sea. Conducting Task Force review missions is one way in which the IAEA will continue its multiyear safety review. “The IAEA said, and I said, that we would be monitoring the controlled discharge of the treated water from the Fukushima Daiichi Nuclear Power Plant before, during and after the operation. The IAEA is here, and we will continue to be here until the very last drop,” Grossi said during his visit to Japan in March.

Image: Design and operations for ALPS treated water discharge (courtesy of Tepco)