International Atomic Energy Agency (IAEA) experts have confirmed that the tritium concentration in the fifth batch of diluted ALPS treated water, which Japan’s Tokyo Electric Power Company (Tepco) is now discharging to the sea is far below the country’s operational limit.

Experts stationed at the IAEA’s office on the site of the Fukushima Daiichi NPP took samples after the treated water was diluted with seawater in the discharge facilities. The IAEA’s independent on-site analysis confirmed that the tritium concentration is far below the operational limit of 1500 becquerels per litre.

The corroboration of data will be also conducted in the fifth batch using interlaboratory comparisons involving both IAEA laboratories as well as independent third-party laboratories from China, South Korea, Switzerland and the US – all of which are members of the network of Analytical Laboratories for the Measurement of Environmental Radioactivity (ALMERA).

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 so that tritium levels fall below national regulations before it is released through an undersea tunnel into the Pacific Ocean.

Japan is discharging the ALPS treated water in batches. The first discharge began in August 2023. The previous four batches – a total of 31,145 cubic metres of water – were also confirmed by the IAEA to have contained tritium concentrations far below operational limits.

Tepco said the latest release, followed safety measures and was closely monitoring by Tepco and the Japanese government, in alignment with international safety standards. It “is part of a comprehensive plan aimed at managing the contaminated water accumulated at the Fukushima Daiichi since the devastating earthquake-triggered tsunami that resulted in a nuclear accident”. Tepco noted that in fiscal year 2023 it had “successfully executed four rounds of the release programme, totalling approximately 31,200 tonnes of treated water” with “plans to discharge a total of 54,600 tonnes in seven rounds during fiscal year 2024”.

The IAEA Task Force conducting the safety review of Japan’s release of the ALPS treated water will reconvene shortly and conduct its second mission to Japan since the start of the water discharges. It is the next in a series of missions that began in 2021 and will continue throughout the IAEA’s safety review of the discharges. IAEA Director General Rafael Mariano Grossi visited Japan in March, as part of his ongoing commitment to monitor the discharge of treated water.

The IAEA’s comprehensive report issued in July 2023 found Japan’s plan for handling the treated water to be consistent with international safety standards and that the release as planned would have a negligible radiological impact to people and the environment. All reports on sampling, independent analysis, data evaluation, as well as timeline, are available on the IAEA website.

Image courtesy of IAEA