How Is Fukushima’s Fallout Affecting Marine Life?
The Fukushima nuclear disaster delivered an unprecedented amount of radioactivity into the sea over a relatively brief time. How did that pulse of cesium and other radioisotopes make its way through the marine food chain? Scott Fowler, who helped pioneer marine radioecology for more than 30 years at the International Atomic Energy Agency’s Marine Environment Laboratories, offered a primer on the subject at the Fukushima and the Ocean Conference in Tokyo in November 2012.
The food chain starts with marine phytoplankton—microscopic plants that account for as much photosynthesis as plants on land. These organisms take up radioactive contaminants from the seawater that surrounds them. As the phytoplankton are eaten by larger zooplankton, small fish, and larger animals up the food chain, some of the contaminants end up in fecal pellets or other detrital particles that settle to the seafloor. These particles accumulate in sediments, and some radioisotopes contained within them may be remobilized back into the overlying waters through microbial and chemical processes.
How much radioactivity gets into marine life depends on a host of factors: How long the organisms are exposed to radioactivity is certainly important, but so too are the sizes and species of the organisms, the radioisotopes involved, the temperature and salinity of the water, how much oxygen is in it, and many other factors such as the life stage of the organisms.
In all this, Fowler said, it’s important to remember the omnipresence of natural background radiation. Polonium-210 and potassium-40 are naturally occurring radioisotopes in the ocean, for example. Potassium-40 is the most abundant radioisotope in the ocean, but polonium-210 accumulates more readily in marine organisms.
“Polonium is responsible for the majority of the radiation dose that fish and other marine organisms receive,” he said.
In an experiment in the early 1980s, Fowler demonstrated vast differences in how much plutonium was absorbed from seawater by marine life across a spectrum of taxonomic groups. Phytoplankton accumulated roughly 10 times as much plutonium as microzooplankton, which took up 100 times more than clams. Octopi and crabs took up about half as much plutonium as clams, but about 100 times more than bottom-dwelling fish.
Another cross-species comparison showed that organisms took up different amounts of radioactivity depending on which particular radioisotopes were out there, he said.
Radioisotopes are also transferred to marine organisms from contaminated sediments—once again in ways that display a complex range of factors, Fowler noted. In one experiment measuring uptake of americium, worms exposed to contaminated sediments took up significantly more of the radioisotope than clams did. But both worms and clams took up much more of the radioisotopes from Pacific sediments, which contain relatively high amounts of silica minerals, than they did from Atlantic sediments, which contain more carbon minerals.
Food is another pathway into marine organisms and “may be in some cases the most important factor in uptake,” Fowler said. Consumed radioisotopes are assimilated internally through the gut, potentially a far more efficient route than if they are absorbed externally from the environment. Marine invertebrates, such as bottom-dwelling starfish and sea urchins, are particularly proficient at absorbing a wide range of ingested radioisotopes, he said, but fortunately, they lose that incorporated radioactivity over time, via excretion.
From plankton to tuna
Fowler’s longtime colleague, Nicholas Fisher, zeroed in on the isotopes that have had the most impact from Fukushima. Fisher, a marine biogeochemist at Stony Brook University, has spent 35 years studying the fate of metals and radioisotopes in marine organisms, including radioisotopes associated with nuclear waste. He and members of his lab participated in the research cruise led by Woods Hole Oceanographic Institution marine geochemist Ken Buesseler off the coast of Japan in June 2011.
Analyzing plankton and fish sampled on the cruise, they consistently found cesium-134 and cesium-137. Not surprisingly, they found no iodine-131, the isotope which along with cesium had been released in highest quantity from the damaged Dai-ichi nuclear power plant. Iodine-131, with its half-life of a mere eight days, was undetectable after a couple of months, Fisher explained.
Cesium, of course, is a different story. The ocean and its denizens continue to bear traces of cesium-137 that date from the atmospheric weapons testing during the Cold War era of the 1960s. Cesium-134, while much shorter-lived, will persist for a number of years.
The chemical properties of radioactive cesium are similar to those of non-radioactive cesium and naturally occurring potassium and sodium, which are abundant in seawater. So all these end up in the same tissues, particularly muscle, of fish and other marine organisms. But potassium and sodium are much less abundant in fresh water, so cesium uptake is much higher in freshwater organisms than in sea life.
Fish also excrete cesium fairly efficiently, losing a few percent per day. So if fish are no longer exposed to new contamination sources, the levels in their tissue should decrease fairly quickly.
Of particular concern for top-level consumers is the potential that these radioisotopes will be concentrated as they make their way up the food chain—what ecologists call biomagnification. Fortunately, cesium shows only modest biomagnification in marine food chains—much less than mercury, a toxic metal, or many other harmful organic compounds such the insecticide DDT and polychlorinated biphenyls (PCBs), Fisher said.
On the 2011 cruise, he and his team measured cesium in everything they sampled. “These were primarily zooplankton and some fish,” he reported. As expected, concentrations were higher in organisms sampled closer to shore. Radioactive silver (110mAg) was also detected in all zooplankton samples. In all cases, however, the amounts of cesium and silver isotopes were much lower than those of naturally occurring potassium-40 in the same samples.
“The radioactivity of the fish we caught and analyzed would not pose problems for human consumption,” he said. Which is not, he noted, the same thing as saying that all marine organisms caught in the region are perfectly safe to eat.
Persistently higher-than-normal levels
What’s puzzling to Fisher, Buesseler, and many other scientists is the persistence of these low but significant levels of radioactivity in the ocean. Jota Kanda, an oceanographer at the Tokyo University of Marine Science and Technology, has extensively studied coastal waters off Fukushima and calculated the amount of cesium still present in coastal waters shallower than 200 meters (660 feet) and in sediments on the seafloor. By his reckoning, what remains is less than three percent of the total discharge, with the rest long since flushed out to the open ocean.
Yet levels of the cesium radioisotopes are still being measured at several tens to hundreds of becquerels per cubic meter in this area, Kanda noted, considerably higher than the levels prior to the Fukushima disaster. More importantly, levels measured in coastal sediments and in some species of fish are higher than those in the surrounding water.
As Kanda sees it, there are three sources responsible for this stubborn presence. One is river runoff—the fallout washed by rainfall into nearby rivers that drain to the sea. He also suggested that a small amount of contaminated water from basement compartments in the reaction unit housing is continuing to leak from the plant itself. But the biggest culprit—the only plausible explanation for the steady levels of radioactive cesium being measured in fish tissue—is continuous input through a food source. And that, he said, points to sediments.
Kanda has estimated that a total of 95 terabecquerels of cesium (1012 becquerels) is present in coastal sediments. The question, he maintained, is how it got there. It could have drifted down to the seafloor in the fecal pellets of plankton that consumed it at the surface—and in fact, plankton in shallow waters sometimes showed elevated levels of cesium. It could also be arriving with organic bits and pieces carried along by river water. It could have adhered to clay particles that came in contact with contaminated water; such radioactive cesium is tightly bound to clay particles and may not be easily transferred to marine life.
Sediment is complex stuff, he explained. Viewed up close, a single grain of what looks like sand is likely a mélange of mineral, organic matter, and pore water—the liquid trapped in the tiny gaps between particles. How contaminants are taken into these agglomerations is not well understood. Echoing Scott Fowler, Kanda noted that the composition and properties of sediments can vary dramatically.
Solving the mystery of the ongoing radioactivity will require a thorough analysis of the seafloor off Fukushima’s coast, he stressed. “Local communities are concerned. They want to know ‘When can we resume fishing?’ We scientists will have to answer this question.”
The key may be how long cesium stays put and the pathways for its uptake into the food chain. Given the 30-year half-life of cesium-137, the sediments could be a possible source of contamination in the food chain for decades to come.
The Accidents at Fukushima
Fukushima and the Ocean Colloquium, May 9, 2013
Fukushima Radiation the Pacific
Lessons from the Japan Earthquake
Café Thorium (Ken Buesseler’s Lab)
WHOI Tsunami website
Fishing for Answers off Fukushima
Radiation and the Oceans
The Fukushima nuclear disaster showed us once again that nuclear reactors are fundamentally dangerous. Not only do they cause significant damage to the environment, the health of populations and to national economies, the heavy financial cost of a meltdown is inevitably borne by the public, not by the companies that designed, built, and operated the plants. None of the world’s 436 nuclear reactors are immune to human errors, natural disasters, or any of the many other serious incidents that could cause a disaster. Millions of people who live near nuclear reactors are at risk.
The lives of hundreds of thousands of people continue to be affected by the Fukushima nuclear disaster, especially the 160,000 who fled their homes because of radioactive contamination, and continue to live in limbo without fair, just, and timely compensation. They have only a false hope of returning home, yet the Japanese government is eagerly pushing to restart reactors, against the will of its people, and without learning true lessons from Fukushima.
Last Updated Nov 21, 2016 11:23 PM EST
TOKYO — An earthquake with magnitude of 6.9 struck Tuesday off the coast of Fukushima prefecture in Japan, the U.S. Geological Survey said.
However, a preliminary magnitude 7.3 earthquake was recorded, the Japan Meteorological Agency said. Both agencies put the depth at just over 6 miles.
The powerful earthquake off the northeast Japanese shore sent residents fleeing to higher ground and prompted worries about the Fukushima nuclear power plant destroyed by a tsunami five year ago.
All tsunami warnings and advisories have been lifted in Japan, seven hours after a powerful offshore earthquake triggered a series of moderate tsunami waves.
The Japan Meteorological Agency warned of waves of up to 10 feet soon after the magnitude 7.4 earthquake and urged residents on sections of the Pacific coast to evacuate to higher ground.
The first tsunamis were recorded about one hour later. The largest one of 4.6 feet in height reached Sendai Bay about two hours after the earthquake.
The tsunami warnings were lifted first, but advisories of possible smaller tsunamis had remained in place until 12:50 p.m.
Waves of around three feet were observed in Soma port in Fukushima, according to Japanese media.
There were reports of minor injuries and damage, Japanese broadcaster NHK said. The earthquake shook buildings in Tokyo, 150 miles southwest of the epicenter.
NHK also showed one person’s video of water rushing up a river or canal, but well within the height of the embankment. It was eerily reminiscent of the 2011 disaster, when much larger tsunamis rushed up rivers and overflowed, wiping away entire neighborhoods.
ON TOP OF RECENT DISASTER
For more than two decades, the global nuclear industry has attempted to frame the debate on nuclear power within the context of climate change: nuclear power is better than any of the alternatives. So the argument went. Ambitious nuclear expansion plans inthe United States and Japan, two of the largest existing markets, and the growth of nuclear power in China appeared to show—superficially at least—that the technology had a future. At least in terms of political rhetoric and media perception, it appeared to be a winning argument. Then came March 11, 2011. Those most determined to promote nuclear power even cited the Fukushima Daiichi accident as a reason for expanding nuclear power: impacts were low, no one died, radiation levels are not a risk. So claimeda handful of commentators in the international (particularly English-language) media.
However,from the start of the accident at Fukushima Daiichi on March 11 2011,the harsh reality of nuclear power was exposed to billions of people across the planet, and in particular to the population of Japan, including the more than 160,000 people displaced by the disaster, many of whom are still unable to return to their homes, and scores of millions more threatened had worst case scenarios occurred. One authoritative voice that has been central to exposing the myth-making of the nuclear industry and its supporters has been that of KanNaoto, Prime Minister in 2011. His conversion from promoter to stern critic may be simple to understand, but it is no less commendable for its bravery. When the survival of half the society you are elected to serve and protect is threatened by a technology that is essentially an expensive way to boil water, then something is clearly wrong. Japan avoided societal destruction thanks in large part to the dedication of workers at the crippled nuclear plant, but also to the intervention of Kan and his staff, and to luck. Had it not been for a leaking pipe into the cooling pool of Unit 4 that maintained sufficient water levels, the highly irradiated spent fuel in the pool, including the entire core only recently removed from the reactor core, would have been exposed, releasing an amount of radioactivity far in excess of that released from the other three reactors. The cascade of subsequent events would have meant total loss of control of the other reactors, including their spent fuel pools and requiring massive evacuation extending throughout metropolitan Tokyo, as Prime Minister Kan feared. That three former Prime Ministers of Japan are not just opposed to nuclear power but actively campaigning against it is unprecedented in global politics and is evidence of the scale of the threat that Fukushima posed to tens of millions ofJapanese.
The reality is thatin terms of electricity share and relative to renewable energy,nuclear power has been in decline globally for two decades.Since the FukushimaDaiichiaccident, this decline has only increased in pace. The nuclear industry knew full well that nuclear power could not be scaled up to the level required to make a serious impact on global emissions. But that was never the point. The industry adopted the climate-change argument as a survival strategy: to ensure extending the life of existing aging reactors and make possible the addition of some new nuclear capacity in the coming decades—sufficient at least to allow a core nuclear industrial infrastructure to survive to mid-century.The dream was to survive to mid-century, when limitless energy would be realized by the deployment of commercial plutonium fast-breeder reactors and other generation IV designs. It was always a myth, but it had a commercial and strategic rationale for the power companies, nuclear suppliers and their political allies.
The basis for the Fukushima Daiichi accident began long before March 11th 2011, when decisions were made to build and operate reactors in a nation almost uniquely vulnerable to major seismic events. More than five years on, the accident continues with a legacy that will stretch over the decades. Preventing the next catastrophic accident in Japan is now a passion of the former Prime Minister, joining as he has the majority of the people of Japan determined to transition to a society based on renewable energy. He is surely correct that the end of nuclear power in Japan is possible. The utilities remain in crisis, with only three reactors operating, and legal challenges have been launched across the nation. No matter what policy the government chooses, the basis for Japan’s entire nuclear fuel cycle policy, which is based on plutonium separation at Rokkasho-mura and its use in the Monju reactor and its fantasy successor reactors, is in a worse state than ever before. But as Kan Naoto knows better than most, this is an industry entrenched within the establishment and still wields enormous influence. Its end is not guaranteed. Determination and dedication will be needed to defeat it. Fortunately, the Japanese people have these in abundance. SB
Q: What is your central message?
Kan: Up until the accident at the Fukushima reactor, I too was confident that since Japanese technology is of high quality, no Chernobyl-like event was possible.
But in fact when I came face to face with Fukushima, I learned I was completely mistaken. I learned first and foremost that we stood on the brink of disaster: had the incident spread only slightly, half the territory of Japan, half the area of metropolitan Tokyo would have been irradiated and 50,000,000 people would have had to evacuate.
Half one’s country would be irradiated, nearly half of the population would have to flee: to the extent it’s conceivable, only defeat in major war is comparable.
That the risk was so enormous: that is what in the first place I want all of you, all the Japanese, all the world’s people to realize.
Q: You yourself are a physicist, yet you don’t believe in the first analysis that people can handle nuclear power? Don’t you believe that there are technical advances and that in the end it will be safe to use?
Kan: As a rule, all technologies involve risk. For example, automobiles have accidents; airplanes, too. But the scale of the risk if an accident happens affects the question whether or not to use that technology. You compare the plus of using it and on the other hand the minus of not using it. We learned that with nuclear reactors, the Fukushima nuclear reactors, the risk was such that 50,000,000 people nearly had to evacuate. Moreover, if we had not used nuclear reactors—in fact, after the incident, there was a period of about two years when we didn’t use nuclear power and there was no great impact on the public welfare, nor any economic impact either. So when you take these factors as a whole into account, in a broad sense there is no plus to using nuclear power. That is my judgment.
One more thing. In the matter of the difference between nuclear power and other technologies, controlling the radiation is in the final analysis extremely difficult.
For example, plutonium emits radiation for a long time. Its half-life is 24,000 years, so because nuclear waste contains plutonium—in its disposal, even if you let it sit and don’t use it—its half-life is 24,000 years, in effect forever. So it’s a very difficult technology to use—an additional point I want to make.
Q: It figured a bit ago in the lecture by Professor Prasser, that in third-generation reactors, risk can be avoided. What is your response?
Kan: It’s as Professor Khwostowa said: we’ve said that even with many nuclear reactors, an event inside a reactor like the Fukushima nuclear accident or a Chernobyl-sized event would occur only once in a million years; but in fact, in the past sixty years, we’ve had Three Mile Island, Chernobyl, Fukushima. Professor Prasser says it’s getting gradually safer, but in fact accidents have happened with greater frequency and on a larger scale than was foreseen. So partial improvements are possible, as Professor Prasser says, but saying that doesn’t mean that accidents won’t happen. Equipment causes accidents, but so do humans.
Q: Today it’s five years after Fukushima. What is the situation in Japan today? We hear that there are plans beginning in 2018 to return the refugees to their homes. To what extent is the clean-up complete?
Kan: Let me describe conditions on site at Fukushima. Reactors #1, #2, #3 melted down, and the melted nuclear fuel still sits in the containment vessel; every day they introduce water to cool it. Radioactivity in the vessel of #2, they say, is 70 sieverts—not microsieverts or millisieverts, 70 sieverts. If humans approach a site that is radiating 70 sieverts, they die within five minutes. That situation has held ever since: that’s the current situation.
Moreover, the water they introduce leaves the containment vessel and is said to be recirculated, but in fact it mixes with groundwater, and some flows into the ocean. Prime Minister Abe used the words “under control,” but Japanese experts, including me, consider it not under control if part is flowing into the ocean. All the experts see it this way.
As for the area outside the site, more than 100,000 people have fled the Fukushima area.
So now the government is pushing residential decontamination and beyond that the decontamination of agricultural land.
Even if you decontaminate the soil, it’s only a temporary or partial reduction in radioactivity; in very many cases cesium comes down from the mountains, it returns.
The Fukushima prefectural government and the government say that certain of the areas where decontamination has been completed are habitable, so people have until 2018 to return; moreover, beyond that date, they won’t give aid to the people who have fled. But I and others think there’s still danger and that the support should be continued at the same level for people who conclude on their own that it’s still dangerous—that’s what we’re saying.
Given the conditions on site and the conditions of those who have fled, you simply can’t say that the clean-up is complete.
Q: Since the Fukushima accident, you have become a strong advocate of getting rid of nuclear reactors; yet in the end, the Abe regime came to power, and it is going in the opposite direction: three reactors are now in operation. As you see this happening, are you angry?
Kan: Clearly what Prime Minister Abe is trying to do—his nuclear reactor policy or energy policy—is mistaken. I am strongly opposed to current policy.
But are things moving steadily backward? Three reactors are indeed in operation. However, phrase it differently: only three are in operation. Why only three? Most—more than half the people—are still resisting strongly. From now on, if it should come to new nuclear plants, say, or to extending the licenses of existing nuclear plants, popular opposition is extremely strong, so that won’t be at all easy. In that sense, Japan’s situation today is a very harsh opposition—a tug of war—between the Abe government, intent on retrogression, and the people, who are heading toward abolishing nuclear reactors.
Two of Prime Minister Abe’s closest advisors are opposed to his policy on nuclear power.
One is his wife. The other is former Prime Minister Koizumi, who promoted him.
Q: Last question: please talk about the possibility that within ten years Japan will do away with nuclear power.
Kan: In the long run, it will disappear gradually. But if you ask whether it will disappear in the next ten years, I can’t say. For example, even in my own party opinion is divided; some hope to do away with it in the 2030s. So I can’t say whether it will disappear completely in the next ten years, but taking the long view, it will surely be gone, for example, by the year 2050 or 2070. The most important reason is economic. It has become clear that compared with other forms of energy, the cost of nuclear energy is high.
Q: Thank you.