More than 12 years after the disaster that closed Japan’s Fukushima Daiichi nuclear power plant, the country will soon dispose of one of the most enduring legacies of the disaster.

Some 1.3 million tonnes of water, most of it used to cool the radioactive material at the core of the plant, will be filtered and cleaned up before being pumped slowly to sea once a 1km pipe is completed in the coming weeks. It may take decades to trickle out the water at a pace slow enough to keep radioactive concentrations at sufficiently low levels – but that has not prevented bitter opposition from some of Japan’s Pacific neighbours.