The updates – made in part due to feedback provided during an ongoing IAEA safety review process – include changes to the radiological environmental impact assessment before the discharge and the associated monitoring programmes. They also include the key issue of characterising the radioactivity in the water.
Japan announced in April 2021 that it planned to discharge more than 1.25 million cubic metres of treated water stored at the station by discharging it into the sea. The plan was approved by the nuclear regulator earlier this year.
The IAEA’s task force, a group of IAEA specialists and external experts from 11 countries, are conducting a multi-year review of the plan’s safety.
As part of its second mission the task force met in Tokyo this week with Tokyo Electric Power Company (Tepco), operator of Fukushima-Daiichi, and the Ministry of Economy, Trade and Industry (Meti).
The water stored at the tanks at the Fukushima-Daiichi site is treated through a process known as advanced liquid processing system (Alps) to remove most of the radioactivity. Tritium, which cannot be removed by Alps, and some very low levels of other radionuclides, remain in the water after processing.
A proper characterisation of the radioactivity in the water is needed for conducting an accurate radiological environmental impact assessment for ensuring safety to people and the environment before the water starts to be released, planned for 2023.
In a report released in May 2022 of the first meeting with Tepco and Meti in February 2022, the task force called for clarification of Tepco’s characterisation of the treated water that will be discharged.
The task force said Japan has now addressed this issue in its amendments.
The task force visited Fukushima-Daiichi to review progress in the design and construction of equipment and facilities for the discharge, including the tunnel that is being built to transport the treated water one kilometre out to sea.
‘No Risk’ To Human Health
Japanese authorities have said there was no practical alternative to releasing the water as storage space ran out. They said there was no risk to human health and that operating nuclear plants around the world release similar water every day.
The water was largely used to cool the three damaged reactor cores, which remain highly radioactive. Some of it has since leaked into basements of the reactor buildings but was collected and stored in tanks.
Space for the tanks is running out and the long-term management of the treated water is necessary to allow for the further decommissioning of Fukushima-Daiichi, which has been permanently shut down since a March 2011 earthquake and tsunami.
Five disposal methods for the water were being considered by the government: controlled discharge into the sea, ground injection, discharge as steam, discharge as hydrogen, and solidification for underground burial.
