At the Fukushima Daiichi site, contaminated water - in part used to cool melted nuclear fuel - is treated by the Advanced Liquid Processing System (ALPS), which removes most of the radioactive contamination, with the exception of tritium. This treated water is currently stored in more than 1000 tanks on site. The total tank storage capacity amounts to about 1.37 million cubic metres and all the tanks are expected to reach full capacity in late 2023 or early 2024.
Japan announced in April 2021 it planned to discharge treated water stored at the site into the sea over a period of about 30 years.
At the meeting today of the Inter-Ministerial Council, the government announced that it had made a decision regarding the start of the discharge of ALPS treated water into the sea.
Prime Minister Fumio Kishida, speaking at a press conference following the meeting, said: "A task that cannot be postponed in order to restore the livelihood of Fukushima and achieve reconstruction is the steady decommissioning of the damaged reactors at the Fukushima Daiichi nuclear power plant." However, he noted the storage of the accumulated water has taken up much of the available space on the site. "We are running out of room to create the necessary space to further steadily advance the decommissioning process of Fukushima Daiichi. In order to overcome this situation, we cannot avoid the disposal of ALPS-treated water, which is a prerequisite for decommissioning."
Tepco said it will "quickly make preparations to commence discharge with the utmost vigilance in accordance with the implementation plan".
The company said that during the initial stages of the discharge, a very small amount will be released using a two-step process. In the first step, which has now begun, a very small amount of ALPS treated water will be diluted with seawater and stored in the vertical discharge shaft (upstream water tank) in order to verify that ALPS treated water is being diluted as planned. After this stored water has been sampled and tritium concentrations measured, it will move on to the second stage, the continuous discharge into the sea, on and after 24 August.
"With our strong determination to prevent reputational damage during this period, Tepco shall devote all of its resources to ensuring the safety and quality of facility operation, speedily obtaining monitoring results and disseminating that information in an accurate and easy-to-understand manner, ensuring transparency through International Atomic Energy Agency (IAEA) reviews, etc., implementing reputational damage countermeasures, and providing suitable compensation should damages be incurred," Tepco said.
When Japan announced the discharge plan in 2021, it asked the IAEA to review its plans against IAEA safety standards. An IAEA Task Force was established to implement the assistance to Japan, which included advice from a group of internationally recognised experts from Member States, including members from the region, under the authority of the IAEA Secretariat.
"Over the past two years the IAEA has conducted a detailed review of the safety related aspects of handling and discharge of ALPS treated water and issued its comprehensive report 4 July 2023," the IAEA said today. "The report concluded that the approach and activities for this discharge are consistent with relevant international safety standards and would have a negligible radiological impact on people and the environment."
The IAEA opened an office at the Fukushima Daiichi plant last month. IAEA staff are working there so that they can continue to monitor and assess activities on site related to the water release to ensure that they continue to be consistent with the safety standards, on the day of the start of the discharge and after.
The IAEA said it will publish available data for use by the global community, including the provision of real-time and near real-time monitoring data.
Some nearby countries have expressed alarm at Japan's plan, but the IAEA says that the level of tritium in the water will be "well below national regulatory limits and the World Health Organization standards for drinking water".
