Japan’s Nuclear Regulation Authority (NRA) has begun a final safety inspection before treated water stored at the Fukushima Daiichi MPP is released into the Pacific Ocean. The inspection began a day after plant operator Tokyo Electric Power Company Holdings (Tepco) installed the last equipment needed for the release – the outlet of the undersea tunnel constructed to release the water 1 kilometre offshore.

A permit for releasing the water could be issued around a week after the inspection is completed after which release of the water could begin, although no date has been announced as yet. The plan has faced continuous protests from local fishermen concerned about safety and reputational damage as well as from South Korea, China and some Pacific Island nations. Chief Cabinet Secretary Hirokazu Matsuno told reporters that the government “abides by its policy of not carrying out a release without the understanding” of fishing groups in Fukushima. He said the government will continue to communicate closely with them and others involved, while ensuring safety and addressing the issue of reputational damage.

NRA approved the plan to release treated water stored at the Fukushima Daiichi NPP in July 2022. The water, used to cool the melted reactor cores in the aftermath of the 2011 nuclear disaster, is stored in around 1,000 huge tanks at the plant containing more than 1.3 million tonnes. Total storage capacity has been reached and NRA has deemed it safe to release the water following treatment although it will still contain traces of tritium, the foreign ministry said in a statement.

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 government therefore plans to dilute the treated water so that tritium levels fall below national regulations before releasing it.

Japan initially announced plans to discharge treated water into the sea over a period of about 30 years in April 2021, asking the International Atomic Energy Agency (IAEA) to review these plans against IAEA safety standards. Tepco submitted the basic design of plans for a treated water dilution/discharge facility and related facilities to the NRA in December 2021. According to the plans, treated water would be diluted with seawater to reduce the amount of tritium to less than one-fortieth of government standards before it is released through the undersea tunnel.

The IAEA has dispatched several missions to Japan since early 2022, and its final evaluation report is expected soon, though the organization has no power to stop the plan. IAEA chief Rafael Mariano Grossi is expected to visit Japan in early July to meet Prime Minister Fumio Kishida and visit the plant.

Earlier in June IAEA said Tepco had demonstrated its capabilities for accurate and precise measurements of the radionuclides present in the treated water stored on site in a report covering its independent sampling and analysis work. This is part of its ongoing review to assess the safety related aspects of the release plan.

The IAEA first observed and facilitated the collection of the treated water samples analysed in the report from tanks at the Fukushima site in March 2022. This water was taken from the first batch of ALPS treated water and further checks have followed. 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 water samples taken have been analysed by Tepco; by the IAEA in its laboratories in Monaco, and in Seibersdorf and Vienna, Austria; and in third-party laboratories in France, South Korea, Switzerland and the USA. All these are members of the network of Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA). Additional samples were taken from other batches of water and are undergoing a similar analysis as part of the wider review process.

The IAEA’s latest report said Tepco has demonstrated a high level of accuracy in their measurements and technical competence and sample collection procedures follow the appropriate methodological standards. It added that 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.

Following NRA’s approval of the water release plan, IAEA Director General Rafael Mariano Grossi appointed a Task Force of independent experts and IAEA staff to review its safety. The Task Force issued its fifth report in May. This is part of a series to be released under the IAEA’s multi-year safety review of the proposed discharge. It focused on Japan’s domestic regulatory review of the water release. This is one component of the international Task Force’s three-pronged review, the other two being the review of technical aspects and conducting independent sampling and analysis. The IAEA’s comprehensive report on its review is being prepared and will be issued in due course.

Image: A Tepco employee explains about the facility to be used to release treated radioactive water into sea (courtesy of AP)