Mix of contaminants in Fukushima wastewater, risks of ocean dumping


Date:
August 6, 2020
Source:
Woods Hole Oceanographic Institution
Summary:
Nearly 10 years after the Tohoku-oki earthquake and tsunami
devastated Japan's Fukushima Dai-ichi Nuclear Power, radiation
levels have fallen to safe levels in all but the waters closest
to the shuttered power plant. A new article looks at 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.



FULL STORY ========================================================================== 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.


========================================================================== "We've watched over the past nine-plus years as the levels of radioactive cesium have declined in seawater and in marine life in the Pacific,"
said Ken Buesseler, a marine chemist at the Woods Hole Oceanographic Institution and author of the new paper. "But there are quite a few
radioactive contaminants still in those tanks that we need to think
about, some of which that were not seen in large amounts in 2011, but
most importantly, they don't all act the same in the ocean." Since 2011, Buesseler has been studying the spread of radiation from Fukushima into
and across the Pacific. In June of that year, he mobilized a team of
scientists to conduct the first international research cruise to study
the early pathways that cesium-134 and -137, two radioactive isotopes
of cesium produced in reactors, were taking as they entered the powerful Kuroshio Current off the coast of Japan. He has also built a network of
citizen scientists in the U.S. and Canada who have helped monitor the
arrival and movement of radioactive material on the Pacific coast of
North America.

Now, he is more concerned about the 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.

"The current focus on tritium in the wastewater holding tanks ignores
the presence other radioactive isotopes in the wastewater," said
Buesseler. "It's a hard problem, but it's solvable. The first step is
to clean up those additional radioactive contaminants that remain in
the tanks, and then make plans based on what remains. Any option that
involves ocean releases would need independent groups keeping track of
all of the potential contaminants in seawater, the seafloor, and marine
life. The health of the ocean -- and the livelihoods of countless people
-- rely on this being done right."

========================================================================== Story Source: Materials provided by
Woods_Hole_Oceanographic_Institution. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Ken O. Buesseler. Opening the floodgates at Fukushima. Science,
07 Aug
2020 DOI: 10.1126/science.abc1507 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200806153610.htm

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