Discharging Fukushima's radioactive water into the open sea is a proposal put to Tokyo by a panel of experts. A marine biochemist explains the consequences of this absurd choice.
Years after the Fukushima nuclear disaster, there is still no solution for disposing of the contaminated water from the Japanese plant struck by the tsunami on 11 March 2011. A panel of experts from Japan's Ministry of Industry recently advised the government led by Prime Minister Shinzo Abe to discharge the radioactive water into the ocean. As far back as last September, Japan's Environment Minister Yoshiaki Harada had identified this option as the only possible solution. The water in question amounts to over one million tonnes of contaminated water that, since the nuclear disaster nine years ago, has been channelled into storage tanks within the plant.
The minister's statement, even at the time, had sparked fierce controversy among Japanese fishermen and environmentalists, even though it has not yet been officially endorsed by the government. The build-up of contaminated water at Fukushima has caused a deadlock in the decommissioning work at the plant. This year, moreover, the Olympics will be held in Tokyo, with some events taking place less than 60 kilometres from the plant. But what would be the implications of a potential disposal solution such as the one proposed by the panel and the minister?
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Ken Buesseler, a marine biochemist at the Woods Hole Oceanographic Institution (Whoi), the largest independent oceanographic research institution in the United States, has been conducting fieldwork at Fukushima periodically since 2011, together with his team. Together with Buesseler, who gave an exclusive interview to LifeGate, we try to shed light on the issues surrounding not only the disposal solution but also the plant's storage system.
Since 2013, a water decontamination facility has been officially in operation, treating water coming from the reactors, which is then stored in the storage tanks. To date, more than one million tonnes of contaminated water have been treated and stored in over a thousand tanks, with one new tank being added per week. According to Tokyo Electric Power Company (Tepco), the electricity company that operates the Fukushima plant, the maximum capacity is 1.37 million tonnes, a figure that will be reached in 2022. After that, there will be no more space.
"They [Tepco management, ed.] say they have no more space, but I think that can be countered," says Buesseler. "An aerial view of the Fukushima storage facility clearly shows that there would be enough space to keep building tanks in the surrounding areas, but perhaps they want to use that space for something else? And yet that land is off-limits for building homes or setting up businesses, so are they choosing not to use space that is not currently being used in any other way? I think they've put the cart before the horse by saying, 'since we're running out of space, let's just dump everything into the sea.'"
The continuous release of radionuclides from Fukushima's tanks and groundwater must be carefully assessed, as the nature and combination of radionuclides is constantly changing. "The problem is not the presence of tritium [a radioactive isotope of hydrogen, ed.] in the tanks, but rather that of other radioactive isotopes. A year ago, Tepco set up a website listing some of these contaminants, such as strontium-90, lithium, iodine-129, and others that have been identified in the tanks in quantities greater than those legally permitted for discharge. The water should therefore be treated, but from reading the data on the website, it is not clear that this is actually happening," Buesseler continues.
"For example, the amount of strontium-90 currently present in the single tank whose data I am looking at turns out to be 10,000 times higher than the amount legally authorised for release. I checked the contaminant levels in March and again just now, shortly before the interview, and in neither case is it clear to me from the data on the website whether they are actually working on removing the most harmful radioactive isotopes."
However, Buesseler adds, there are possible alternatives for disposing of the contaminated water. One of these is based on the so-called half-life of radioactive isotopes — that is, the time it takes for half the initial mass of a radioactive chemical element to decay.
"Tritium has a half-life of about twelve years, after which there is a 50 per cent radioactive decay. Eight years have already passed since 2011, so there is less tritium now than there was then," explains Buesseler. "If they were to wait another 60 years, and in the meantime build new tanks, 97 per cent of the tritium would be consumed through radioactive decay. Those 60 years would give us a 97 per cent radioactive reduction. Of course, we won't be able to get rid of it entirely, but we can certainly ensure there is a significant reduction."
The minister added in his statement that the contaminated water would be diluted before being discharged into the sea. Would this process make the contaminated water less harmful? "Diluting the water might help reduce the impact of isotopes such as tritium, but as for the other contaminants like strontium, lithium or cobalt, the total quantity released would be the same and would then accumulate in the biota and on the seabed," explains Buesseler.
"Tritium is like a form of water and would therefore move with the currents, whereas the other isotopes would end up building up and creating a localised concentration harmful to fish. The chemistry for each of the radionuclides is different, which is why it is important to pre-monitor and act accordingly," Buesseler continues.
Even if the radioactive water were discharged into the oceans, it is the currents that dictate its direction. It would accumulate on the ocean floor or in the marine biota, following the currents.Ken Buesseler, Whoi
Each of these contaminating isotopes behaves differently in the ocean and in ocean fauna. Strontium-90, for example, is problematic because it mimics the behaviour of calcium, ending up accumulating in the bones of fish — unlike tritium, which passes through fish quickly as though it were water. According to Buesseler, it would be appropriate to set up a continuous, independent monitoring system, which in this case does not appear to have been considered yet.
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"My view is that there should be independent monitoring not only of each of the storage tanks to understand what is inside them, but also of radioactive isotope levels in the oceans following any potential discharge. Instead, I have not heard of any programme for this kind of monitoring, so the minister's statement struck me as truly hasty," Buesseler continues.
"Obviously, having a radioactive water storage facility in a seismic zone is also problematic, so it is always a matter of making a trade-off between risks."
And is there anything that can be done at an engineering level? "Initially the walls of the tanks were bolted together, making them vulnerable to leaks. Now the tanks are welded, but in any case none of these cisterns was built with the aim of lasting 60 years, so new, larger seismic-resistant tanks would need to be built," explains Buesseler.
The minister's statement had not only brought the problems surrounding the Fukushima plant back to the fore, but had naturally provoked an outcry from fishing associations. In recent years, in fact, the price of fish on the market had returned to pre-2011 nuclear disaster levels.
"The good news for Japan is that over the past four years the fish coming from the coastal areas of Fukushima, which has been continuously tested for radioactivity since 2011, has never exceeded the permitted toxicity threshold set by strict standards," confirms Buesseler. "So they are also coming from a phase of reopening of the fish market."
Releasing contaminated water into the open sea would therefore be a problem involving other states as well. South Korea, for example, has expressed its concerns. Seoul, which has yet to lift the ban introduced in 2013 to halt the import of fish from Fukushima, declared last week that disposing of contaminated water in the oceans would represent a "grave threat" to the marine environment. Japanese fisheries officials have pointed out, however, that under a rigorous testing regime, the sale of any fish containing more than 50 becquerels of radioactive material per kilogram is prohibited — a threshold far lower than the 100 becquerels per kilogram standard observed in the rest of Japan.
According to Buesseler, there does not appear to be a genuine risk for South Korea. "The oceans don't flow in their direction. Even if the radioactive waters were discharged into the oceans, it is the currents that dictate the direction. They would accumulate on the ocean floor or in the marine biota, following the currents. There is a very strong current to the south of Japan, the Kuroshio current, which reaches as far as the Bering Strait — I call it the Pacific Gulf Stream. That's why in 2011, after the Fukushima accident, everyone on the west coast of the United States was worried. They thought the radiation would reach all the way there, and indeed it did, even if only in measurable trace quantities. Countries like South Korea have very little to worry about."
And yet, it must be taken into account that, in cases like this, what matters is consumer perception. Disposing of radioactive water in the ocean would short-circuit the fishing industry across the region.
"What the minister said doesn't seem to me to be the right message if you want to promote Japanese fish. Public perception is such that any disposal of contaminated water in the ocean would deter consumers from buying fish from that region," states Buesseler. "Regardless of whether the health risk is real or not, there is a perception of high risk."
Perhaps that is precisely why the Japanese government has not, until now, officially endorsed its minister's statement. The experts' recommendations will also need to be officially received by the committee's chair, Professor Ichiro Yamamoto of Nagoya University, and presented to the government at a later date that has yet to be set.
"The government, as far as I know, has not yet decided what to do with the water in the tanks," concludes Buesseler, "but in any case I doubt they will get moving before the Tokyo 2020 Olympics."