In 2011, a massive earthquake off the coast of Japan resulted in a tsunami that wrecked the facility beyond repair. Since then, the plant has been producing around 100m³ of contaminated water as part of efforts to keep the reactors cool since the meltdown.

In the following 12 years, the plant’s operator Tokyo Electric Power Company (Tepco) has accumulated 1.34 million tonnes of water – enough to fill 500 Olympic-size pools – but has run out of storage space.

Japanese authorities subsequently agreed to begin releasing some of the plant’s treated wastewater into the Pacific Ocean, much to the chagrin of Chinese authorities, who expressed concern over its environmental impact and banned Japanese seafood as a result.

But Tepco has been filtering the contaminated water to remove most of the radioactive isotopes, leaving only tritium, a radioactive isotope of hydrogen that is hard to separate.

Tritium is considered mostly harmless to humans, especially in the...