Newly revealed reactor damage could hinder Fukushima water release

The Fukushima nuclear power plant.

On 4 April, the Tokyo Electric Power Company (TEPCO) released photos showing extensive damage to a containment chamber at the Fukushima nuclear power plant.

The photos, taken at the end of March by a robotic probe inside the primary containment chamber of the plant's Unit 1, showed that the pedestal, a concrete supporting structure over a meter thick located directly beneath the reactor core, suffered significant damage near its bottom, exposing the steel reinforcement bars inside.

The photos revealed more than half of the base had corroded. The length of the probe’s cable prevented seeing the other half, but it’s likely to have similar damage. As the pedestal supports the core, which contains nuclear fuel, its condition raised concerns about its future earthquake resistance. Experts from the Japan Atomic Energy Institute said the damage was more serious than expected.

TEPCO revealed the photos to the media a day before the release of a generally positive report from an International Atomic Energy Agency (IAEA) Fukushima taskforce, reviewing the safety of Japan’s plan to discharge treated cooling water from the Fukushima Daiichi Fukushima Daiichi Nuclear Power Station into the sea.

The plan to discharge the water has been controversial. While it has the backing of the IAEA, China and South Korea opposed it, saying that Japan shouldn’t unilaterally decide the matter. Both countries maintain bans on seafood from Fukushima and nearby prefectures, and for other prefectures, they require a certificate of pre-export testing of radionuclides.

"I would like to stress that Japan’s release of treated, nuclear-contaminated water from the Fukushima plant concerns the global marine environment and public health, which is not a private matter for the Japanese side,” Chinese Foreign Ministry Spokesperson Mao Ning said at a daily briefing.

On 11 April, the South Korean government, issued a statement refuting speculation the country’s newly elected president had softened the country’s stance on the release as part of an effort to improve relations with Japan.

“[It is] completely untrue, as it contradicts our government's position of prioritizing the health and safety of the people,” the statement said.

Neither government has officially commented on TEPCO’s revelation of new damage.

Other countries, such as the U.K., have lifted restrictions on Fukushima seafood, but some others still maintain a testing requirement. The Japanese government’s most-recent update on export requirements is outlined in the document “Procedures required for exporting marine products and processed marine products from Japan (list by country/region) (as of April 1, 2023).”  

Most provinces in China have banned seafood imports from 10 Japanese prefectures (Miyagi, Fukushima, Ibaraki, Tochigi, Gunma, Saitama, Chiba, Tokyo, Niigata, and Nagano). For all other prefectures, a radioactive material inspection certificate and certificate of origin are required for all seafood imports. Macau bans imports from nine Japanese prefectures (Miyagi, Ibaraki, Tochigi, Gunma, Saitama, Chiba, Tokyo, Niigata, and Nagano).

South Korea bans imports from eight prefectures (Aomori, Miyagi, Iwate, Fukushima, Ibaraki, Tochigi, Gunma, and Chiba) and requires the certificates for imports from eight others (Hokkaido, Tokyo, Kanagawa, Aichi, Mie, Ehime, Kumamoto, and Kagoshima).

Countries or regions that allow imports, but still require a radioactive material inspection certificate and certificate of origin include Taiwan (which also inspects upon import) and Hong Kong.  The European Union requires the inspection certificate for Fukushima and Gunma prefectures only.

The IAEA report, compiled for the plant operator TEPCO and the Ministry of Economy, Trade, and Industry (METI), presents the findings from the taskforce’s second mission in November of 2022 – before the robotic probe found the damage to the plant’s pedestal. It assesses TEPCO’s technical responsibilities including the safety-related aspects of the systems built to discharge the Advanced Liquid Processing System (ALPS)-treated water, the radiological environmental impact assessment, source and environmental monitoring programs, and occupational radiation protection.

Although the IAEA may be interested in how the newly discovered damage will affect the current safety or future decommissioning of the plant, it’s not likely to directly affect the plan to release the treated cooling water, therefore falling outside the scope of the current taskforce’s work.

The taskforce said TEPCO’s revised methodology for characterizing the source term is sufficiently conservative yet realistic. “Source term” refers to the types and amounts of radioactive or hazardous material released to the environment following an accident. The task force gained a better understanding of TEPCO’s environmental monitoring programs and agreed that they are comprehensive, and it confirmed that TEPCO has a reliable and sustainable radiation protection program for its employees.

This was the fourth taskforce report published under the IAEA’s multi-year safety review of the planned ALPS-treated water. IAEA Director General Rafael Mariano Grossi appointed the task force of independent experts and IAEA staff in 2021, following a request from Japan.

The taskforce said it would need to ..

Photo courtesy of Santiherllor/Shutterstock

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