Should Japan dump Fukushima's radioactive water into the ocean?

Nuclear experts from the International Atomic Energy Agency (IAEA) have formally backed Japan’s controversial plan to release radioactive wastewater from the Fukushima Daiichi nuclear power plant into the Pacific Ocean – but is it the right thing to do?

In 2011, Japan was hit by a serious earthquake and tsunami, which caused the meltdown of three reactors at Fukushima. The contaminated water, which is currently sitting in roughly 1000 giant tanks on site, was used to keep Fukushima’s reactors and debris cool following the disaster.

Japan wants to gradually release 1.3 million cubic metres of this water into the sea over the next three to four decades, so it can continue decommissioning of the Fukushima site.

In a report issued on 4 June, the IAEA concluded that the approach will have “a negligible radiological impact on people and the environment”. IAEA director general Rafael Mariano Grossi said in the report that Japan’s plans were “consistent with relevant international safety standards”.

The water has already been treated to remove 62 radioactive contaminants, but it remains tainted by tritium, a radioactive isotope of hydrogen. Because tritium is bonded to the water molecule itself, it is challenging to remove, says Ian Farnan at the University of Cambridge. “It’s not possible, really, to separate [tritium from water],” he says.

Tritium, which has a radioactive half-life of just over 12 years, emits low-energy beta particles and does little damage to cells, says Farnan. Because of its bond with water, it will pass through most marine organisms without causing harm, he says. Many nuclear plants around the world already discharge tritium into the ocean.

Japan says it must start discharging the water soon because the tanks will hit capacity in 2024. It insists the wastewater will be diluted to ensure levels of tritium never exceed World Health Organization guidelines.

But China, South Korea and Pacific Island nations have expressed doubts over Japan’s discharge plan, amid fears the wastewater release could contaminate the marine food chain. In January, Henry Puna of the Pacific Islands Forum said it has “grave concerns” about the proposed ocean release.

A 2021 study suggested that if the contaminated wastewater were released gradually, spikes in tritium concentrations would be confined to the east coast of Japan – and would represent only a tiny fraction of the background concentration of tritium already present in the ocean.

Awadhesh Jha at the University of Plymouth, UK, warns that more research is needed to investigate the risks tritium poses to the marine food chain. Jha’s laboratory experiments suggest tritium can accumulate in the tissues of shellfish such as mussels and oysters, but little is known about the impact of real-world exposure. “It needs an international [research] effort,” he says.

Meanwhile, Tokyo Electric Power Company, the firm that runs the site, has admitted that water in the tanks will need additional, “secondary” treatment to filter out more dangerous isotopes, such as ruthenium-106, cobalt-60 and strontium-90, in order to meet regulatory standards.

Ken Buesseler at the Woods Hole Oceanographic Institution in Massachusetts is concerned these other isotopes could pose a threat to marine life.  “Unlike tritium, cobalt-60 is 300,000 times more likely to accumulate on the seafloor at the outlet of the pipes,” he says. “It will build up over time, it will accumulate. So whatever amount you put in, it doesn’t just dilute away.” As a result, cobalt-60 could be ingested by bottom dwelling fish, he warns, entering the marine food chain.

Ultimately, Jha says the Japanese authorities have no choice but to discharge the contaminated water into the ocean, particularly given the earthquake risk of storing it on land. “They don’t have any other options,” he says.

Buesseler disagrees. He has proposed the contaminated water is treated to remove dangerous isotopes, and then used to make concrete for use on the Fukushima site or to construct coastal tsunami barriers.

The potential for radiation exposure to the public would be essentially eliminated with this approach, Buesseler argues. “Once the tritium is in something as stable as concrete, the radiation can’t escape,” he says.