Nearly 10 years after the Tohoku-oki earthquake and tsunami devastated Japan’s Fukushima Dai-ichi Nuclear Power Plant and triggered an unprecedented release radioactivity into the ocean, radiation levels have fallen to safe levels in all but the waters closest to the shuttered power plant. Today, fish and other seafood caught in waters beyond all but a limited region have been found to be well within Japan’s strict limits for radioactive contamination, but a new hazard exists and is growing every day in the number of storage tanks on land surrounding the power plant that hold contaminated wastewater. An article published August 8 in the journal Science takes a look at some of the many radioactive elements contained in the tanks and suggests that more needs to be done to understand the potential risks of releasing wastewater from the tanks into the ocean.
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more than 1,000 tanks on the grounds of the power plant filling with ground water and cooling water that have become contaminated through contact with the reactors and their containment buildings. Sophisticated cleaning processes have been able to remove many radioactive isotopes and efforts to divert groundwater flows around the reactors have greatly reduced the amount of contaminated water being collected to less than 200 metric tons per day, but some estimates see the tanks being filled in the near future, leading some Japanese officials to suggest treated water should be released into the ocean to free up space for more wastewater.
One of the radioactive isotopes that remains at the highest levels in the treated water and would be released is tritium, an isotope of hydrogen is almost impossible to remove, as it becomes part of the water molecule itself. However, tritium has a relatively short half-life, which measures the rate of decay of an isotope; is not absorbed as easily by marine life or seafloor sediments, and produces beta particles, which is not as damaging to living tissue as other forms of radiation. Isotopes that remain in the treated wastewater include carbon-14, cobalt-60, and strontium-90. These and the other isotopes that remain, which were only revealed in 2018, all take much longer to decay and have much greater affinities for seafloor sediments and marine organisms like fish, which means they could be potentially hazardous to humans and the environment for much longer and in more complex ways than tritium.
— source by Woods Hole Oceanographic Institution | Aug 6, 2020