Japan will start releasing treated and diluted radioactive wastewater from the Fukushima Daiichi nuclear plant into the Pacific Ocean as early as Thursday — a controversial step that the government says is essential for the decades of work needed to shut down the facility that had reactor meltdowns 12 years ago.
Usually to consider radioactive sources “gone” you have to wait at least 5 half lives (which makes it 99.875% gone), which would be 60 years in this case.