Clearing the radioactive rubble heap that was Fukushima Daiichi, 7 years on — Scientific American

” Seven years after one of the largest earthquakes on record unleashed a massive tsunami and triggered a meltdown at Japan’s Fukushima Daiichi nuclear power plant, officials say they are at last getting a handle on the mammoth task of cleaning the site before it is ultimately dismantled. But the process is still expected to be a long, expensive slog, requiring as-yet untried feats of engineering—and not all the details have yet been worked out.

When the disaster knocked out off- and on-site power supplies on March 11, 2011, three of the cooling systems for the plant’s four reactor units were disabled. This caused the nuclear fuel inside to overheat, leading to a meltdown and hydrogen explosions that spewed out radiation. The plant’s operator, Tokyo Electric Power Co. (TEPCO), responded by cooling the reactors with water, which continues today. Meanwhile thousands of people living in the surrounding area were evacuated and Japan’s other nuclear plants were temporarily shut down.

In the years since the disaster and the immediate effort to stanch the release of radioactive material, officials have been working out how to decontaminate the site without unleashing more radiation into the environment. It will take a complex engineering effort to deal with thousands of fuel rods, along with the mangled debris of the reactors and the water used to cool them. Despite setbacks, that effort is now moving forward in earnest, officials say. “We are still conducting studies on the location of the molten fuel, but despite this we have made the judgment that the units are stable,” says Naohiro Masuda, TEPCO’s chief decommissioning officer for Daiichi.

Completely cleaning up and taking apart the plant could take a generation or more, and comes with a hefty price tag. In 2016 the government increased its cost estimate to about $75.7 billion, part of the overall Fukushima disaster price tag of $202.5 billion. The Japan Center for Economic Research, a private think tank, said the cleanup costs could mount to some $470 billion to $660 billion, however.

Under a government roadmap, TEPCO hopes to finish the job in 30 to 40 years. But some experts say even that could be an underestimate. “In general, estimates of work involving decontamination and disposal of nuclear materials are underestimated by decades,” says Rod Ewing, a professor of nuclear security and geological sciences at Stanford University. “I think that we have to expect that the job will extend beyond the estimated time.”

The considerable time and expense are due to the cleanup being a veritable hydra that involves unprecedented engineering. TEPCO and its many contractors will be focusing on several battlefronts.

Water is being deliberately circulated through each reactor every day to cool the fuel within—but the plant lies on a slope, and water from precipitation keeps flowing into the buildings as well. Workers built an elaborate scrubbing system that removes cesium, strontium and dozens of other radioactive particles from the water; some of it is recirculated into the reactors, and some goes into row upon row of giant tanks at the site. There’s about one million tons of water kept in 1,000 tanks and the volume grows by 100 tons a day, down from 400 tons four years ago.

To keep more water from seeping into the ground and being tainted, more than 90 percent of the site has been paved. A series of drains and underground barriers—including a $325-million* supposedly impermeable “wall” of frozen soil—was also constructed to keep water from flowing into the reactors and the ocean. These have not worked as well as expected, though, especially during typhoons when precipitation spikes, so groundwater continues to be contaminated.

Despite the fact contaminated water was dumped into the sea after the disaster, studies by Japanese and foreign labs have shown radioactive cesium in fish caught in the region has fallen and is now within Japan’s food safety limits. TEPCO will not say when it will decide what to do with all the stored water, because dumping it in the ocean again would invite censure at home and abroad—but there are worries that another powerful quake could cause it to slosh out of the tanks.

Fuel Mop-up

A second major issue at Fukushima is how to handle the fuel¾the melted uranium cores as well as spent and unused fuel rods stored at the reactors. Using robotic probes and 3-D imaging with muons (a type of subatomic particle), workers have found pebbly deposits and debris at various areas inside the primary containment vessels in the three of the plant’s reactor units. These highly radioactive remains are thought to be melted fuel as well as supporting structures. TEPCO has not yet worked out how it can remove the remains, but it wants to start the job in 2021. There are few precedents for the task. Lake Barrett—director of the Three Mile Island nuclear plant during its decommissioning after a partial meltdown at the Middletown, Pa., facility in 1979—says TEPCO will use robots to remotely dig out the melted fuel and store it in canisters on-site before shipping to its final disposal spot. “This is similar to what we did at Three Mile Island, just much larger and with much more sophisticated engineering because their damage is greater than ours was,” Barrett says. “So although the work is technically much more challenging than ours was, Japan has excellent technological capabilities, and worldwide robotic technology has advanced tremendously in the last 30-plus years.”

Shaun Burnie, senior nuclear specialist with Greenpeace Germany, doubts the ambitious cleanup effort can be completed in the time cited, and questions whether the radioactivity can be completely contained. Until TEPCO can verify the conditions of the molten fuel, he says, “there can be no confirmation of what impact and damage the material has had” on the various components of the reactors—and therefore how radiation might leak into the environment in the future.

Although the utility managed to safely remove all 1,533 fuel bundles from the plant’s unit No. 4 reactor by December 2014, it still has to do the same for the hundreds of rods stored at the other three units. This involves clearing rubble, installing shields, dismantling the building roofs, and setting up platforms and special rooftop equipment to remove the rods. Last month a 55-ton dome roof was installed on unit No. 3 to facilitate the safe removal of the 533 fuel bundles that remain in a storage pool there. Whereas removal should begin at No. 3 sometime before April 2019, the fuel at units No. 1 and 2 will not be ready for transfer before 2023, according to TEPCO. And just where all the fuel and other radioactive solid debris on the site will be stored or disposed of long-term has yet to be decided; last month the site’s ninth solid waste storage building, with a capacity of about 61,000 cubic meters, went into operation.

As for what the site itself might look like decades from now, cleanup officials refuse to say. But they are quick to differentiate it from the sarcophagus-style containment of the 1986 Chernobyl catastrophe in the Soviet Union, in what is now Ukraine. Whereas the Chernobyl plant is sealed off and the surrounding area remains off-limits except for brief visits—leaving behind several ghost towns—Japanese officials want as many areas as possible around the Daiichi site to eventually be habitable again.

“To accelerate reconstruction and rebuilding of Fukushima as a region, and the lives of locals, the key is to reduce the mid- and long-term risk,” says Satoru Toyomoto, director for international issues at the Ministry of Economy, Trade and Industry’s Nuclear Accident Response Office. “In that regard, keeping debris on the premises without approval is not an option.” ”

by Tim Hornyak, Scientific American

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Japan still at a stalemate as Fukushima’s radioactive water grows by 150 tons a day — The Japan Times

” More than six years after a tsunami overwhelmed the Fukushima No. 1 nuclear power plant, Japan has yet to reach consensus on what to do with a million tons of radioactive water, stored on site in around 900 large and densely packed tanks that could spill should another major earthquake or tsunami strike.

The stalemate is rooted in a fundamental conflict between science and human nature.

Experts advising the government have urged a gradual release to the Pacific Ocean. Treatment has removed all the radioactive elements except tritium, which they say is safe in small amounts. Conversely, if the tanks break, their contents could slosh out in an uncontrolled way.

Local fishermen are balking. The water, no matter how clean, has a dirty image for consumers, they say. Despite repeated tests showing most types of fish caught off Fukushima are safe to eat, diners remain hesitant. The fishermen fear any release would sound the death knell for their nascent and still fragile recovery.

“People would shun Fukushima fish again as soon as the water is released,” said Fumio Haga, a drag-net fisherman from Iwaki, a city about 50 kilometers (30 miles) down the coast from the nuclear plant.

And so the tanks remain.

Fall is high season for saury and flounder, among Fukushima’s signature fish. It was once a busy time of year when coastal fishermen were out every morning.

Then came March 11, 2011. A magnitude 9 offshore earthquake triggered a tsunami that killed more than 18,000 people along the coast. The quake and massive flooding knocked out power for the cooling systems at the Fukushima nuclear plant. Three of the six reactors had partial meltdowns. Radiation spewed into the air, and highly contaminated water ran into the Pacific.

Today, only about half of the region’s 1,000 fishermen go out, and just twice a week because of reduced demand. They participate in a fish testing program.

Lab technicians mince fish samples at Onahama port in Iwaki, pack them in a cup for inspection and record details such as who caught the fish and where. Packaged fish sold at supermarkets carry official “safe” stickers.

Only three kinds of fish passed the test when the experiment began in mid-2012, 15 months after the tsunami. Over time, that number has increased to about 100.

The fish meet what is believed to be the world’s most stringent requirement: less than half the radioactive cesium level allowed under Japan’s national standard and one-twelfth of the U.S. or EU limit, said Yoshiharu Nemoto, a senior researcher at the Onahama testing station.

That message isn’t reaching consumers. A survey by the Consumer Affairs Agency in October found that nearly half of Japanese weren’t aware of the tests, and that consumers are more likely to focus on alarming information about possible health impacts in extreme cases, rather than facts about radiation and safety standards.

Fewer Japanese consumers shun fish and other foods from Fukushima than before, but 1 in 5 still do, according to the survey. The coastal catch of 2,000 tons last year was 8 percent of pre-disaster levels. The deep-sea catch was half of what it used to be, though scientists say there is no contamination risk that far out.

Naoya Sekiya, a University of Tokyo expert on disaster information and social psychology, said that the water from the nuclear plant shouldn’t be released until people are well-informed about the basic facts and psychologically ready.

“A release only based on scientific safety, without addressing the public’s concerns, cannot be tolerated in a democratic society,” he said. “A release when people are unprepared would only make things worse.”

He and consumer advocacy group representative Kikuko Tatsumi sit on a government expert panel that has been wrestling with the social impact of a release and what to do with the water for more than a year, with no sign of resolution.

Tatsumi said the stalemate may be further fueling public misconception: Many people believe the water is stored because it’s not safe to release, and they think Fukushima fish is not available because it’s not safe to eat.

The amount of radioactive water at Fukushima is still growing, by 150 tons a day.

The reactors are damaged beyond repair, but cooling water must be constantly pumped in to keep them from overheating. That water picks up radioactivity before leaking out of the damaged containment chambers and collecting in the basements.

There, the volume of contaminated water grows, because it mixes with groundwater that has seeped in through cracks in the reactor buildings. After treatment, 210 tons is reused as cooling water, and the remaining 150 tons is sent to tank storage. During heavy rains, the groundwater inflow increases significantly, adding to the volume.

The water is a costly headache for Tokyo Electric Power Company Holdings Inc., the utility that owns the plant. To reduce the flow, it has dug dozens of wells to pump out groundwater before it reaches the reactor buildings and built an underground “ice wall” of questionable effectiveness by partially freezing the ground around the reactors.

Another government panel recommended last year that the utility, known as Tepco, dilute the water up to about 50 times and release about 400 tons daily to the sea — a process that would take almost a decade to complete. Experts note that the release of tritiated water is allowed at other nuclear plants.

Tritiated water from the 1979 Three Mile Island accident in the United States was evaporated, but the amount was much smaller, and still required 10 years of preparation and three more years to complete.

A new chairman at Tepco, Takashi Kawamura, caused an uproar in the fishing community in April when he expressed support for moving ahead with the release of the water.

The company quickly backpedaled, and now says it has no plans for an immediate release and can keep storing water through 2020. Tepco says the decision should be made by the government, because the public doesn’t trust the utility.

“Our recovery effort up until now would immediately collapse to zero if the water is released,” Iwaki abalone farmer Yuichi Manome said.

Some experts have proposed moving the tanks to an intermediate storage area, or delaying the release until at least 2023, when half the tritium that was present at the time of the disaster will have disappeared naturally. ”

by Mari Yamaguchi, The Japan Times

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Poison in the air — The New International, Opinion

” Three of the six reactors at Japan’s Fukushima-Daiichi complex were wrecked in March 2011 by an earthquake and tsunami. The destruction of emergency electric generators caused a ‘station blackout’ which halted cooling water intake and circulation. Super-heated, out-of-control uranium fuel in reactors 1, 2, and 3 then boiled off cooling water, and some 300 tons of fuel ‘melted’ and burned through the reactors’ core vessels, gouging so deep into underground sections of the structure that to this day operators aren’t sure where it is. Several explosions in reactor buildings and uncovered fuel rods caused the spewing of huge quantities of radioactive materials to the atmosphere, and the worst radioactive contamination of the Pacific Ocean ever recorded. Fukushima amounts to Whole-Earth poisoning.

Now, researchers say, radioactive isotopes that were spread across Japan (and beyond) by the meltdowns will continue to contaminate the food supply for a very long time.

According to a new study that focused on ‘radiocaesium’ – as the British call cesium-134 and cesium-137 – ‘food in japan will be contaminated by low-level radioactivity for decades’. The official university announcement of this study neglected to specify that Fukushima’s cesium will persist in the food chain for thirty decades. It takes 10 radioactive half-lives for cesium-137 to decay to barium, and its half-life is about 30 years, so C-137 stays in the environment for roughly 300 years.

The study’s authors, Professor Jim Smith, of the University of Portsmouth, southwest of London, and Dr. Keiko Tagami, from the Japanese National Institute of Radiological Sciences, report that cesium-caused ‘radiation doses in the average diet in the Fukushima region are very low and do not present a significant health risk now or in the future’.

This phraseology deliberately conveys a sense of security – but a false one. Asserting that low doses of radiation pose no ‘significant’ health risk sounds reassuring, but an equally factual framing of precisely the same finding is that small amounts of cesium in food pose a slightly increased risk of causing cancer.

This fact was acknowledged by Prof Smith in the June 14 University of Portsmouth media advisory that announced his food contamination study, which was published in Science of the Total Environment. Because of above-ground atom bomb testing, Prof. Smith said, “Radioactive elements such as caesium-137, strontium-90 and carbon-14 contaminated the global environment, potentially causing hundreds of thousands of unseen cancer deaths”.

No less an authority than the late John Gofman, MD, Ph D, a co-discoverer of plutonium and Professor Emeritus of molecular and cell biology at the University of California, spent 50 years warning about the threat posed by low doses of radiation. In May 1999, Gofman wrote, “By any reasonable standard of biomedical proof, there is no safe dose, which means that just one decaying radioactive atom can produce permanent mutation in a cell’s genetic molecules. My own work showed this in 1990 for X rays, gamma rays, and beta particles.”

The Fukushima-borne cesium in Japan’s food supply, and in the food-web of the entire Pacific Ocean, emits both beta and gamma radiation. Unfortunately, it will bio-accumulate and bio-concentrate for 300 years, potentially causing, as Dr Gofman if not Dr Smith might say, hundreds of thousands of unseen cancer deaths. ”

originally published in CounterPunch

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‘Yoshida’s Dilemma: One Man’s Struggle to Avert Nuclear Catastrophe’: But for him, Fukushima could have been much worse — The Japan Times

” Disaster response, even at its most heroic, can fall to people who would rather be somewhere else.

So it was for Masao Yoshida, who, while helming the Fukushima No. 1 nuclear power plant during the disaster in 2011, gave the groan, “Why does this happen on my shift?”

But in some ways Yoshida, an industry veteran of 32 years, was the right man to handle the crisis. His leadership during those days on the edge, at times in defiance of orders from the top of the utility that employed him, is at the center of Rob Gilhooly’s new book “Yoshida’s Dilemma: One Man’s Struggle to Avert Nuclear Catastrophe.”

Gilhooly writes from the eye of the storm, putting the reader in the plant’s control room with almost claustrophobic immediacy. One of his challenges was to render the emergency in real-time. How much can prose, moving forward in measured steps, convey a lethal technology unraveling in extremis? How do you convey the breakdown of machinery without getting mired in technical detail?

“It was difficult,” says Gilhooly, who spent almost four years researching and writing the book. “What struck me about the plant workers — it sounded like complete chaos. My decision was not to make it sound orderly. I wanted it to appear chaotic, without the writing becoming chaotic itself. I tore my hair out over the technical details, because I wanted the book to be readable.”

In the end, the book is a cumulative experience — an intense ride that rewards endurance. Gilhooly weaves in the history of nuclear energy in Japan, interviews with experts and re-created conversations among the plant workers.

“Yoshida was a straight talker from Osaka — a larger-than-life personality,” says Gilhooly, who interviewed the superintendent off the record. “He was different from the other superintendents, more prepared to stick his neck out. He was sharper, more bloody-minded. When tipping his hat to authority, he may have done so with a quietly raised middle finger.”

This attitude might have saved lives, when, after a hydrogen blast at the No. 1 plant, Tepco HQ in Tokyo ordered staff to evacuate. Yoshida knew that the executives had little idea of what was actually happening at the plant. Going behind the backs of his superiors, he contacted then-Prime Minister Naoto Kan, insisting that leaving the plant would be reckless. The utility also ordered that seawater not be pumped through the reactor as coolant, since that would render it useless for energy generation in the future. Exposed to life-threatening levels of radiation, Yoshida and his team defied the order, scrambling to cool the overheating reactor with seawater.

The desperate move worked. The team managed to cool the reactor, and later the Fukushima Nuclear Accident Independent Investigation Commission, which was authorized by the Diet, concluded in its report that “(Yoshida’s) disregard for corporate instructions was possibly the only reason that the reactor cores didn’t explode.”

In Western media coverage of the Fukushima disaster, much was made of Japanese groupthink. A culturally ingrained obedience and a reluctance to question authority was blamed in part for the disaster. Still, the responses vary, and some staff put safety concerns over company loyalty.

“I didn’t want to editorialize,” says Gilhooly, who writes with a calm, thoughtful voice, avoiding the temptation of melodrama. “But yes, Yoshida — and others — refuted the stereotype that was used to explain parts of the disaster.”

Gilhooly is talking to a Japanese publisher, but thinks a translated version may prove difficult: His sources spoke freely about the events at the plant assuming the interviews wouldn’t be published in Japanese. Still, Gilhooly, who takes a stand in the book against using nuclear energy, hopes to fuel the ongoing debate in his adopted home.

“I just wanted to know the truth,” he says. “There is a discussion that needs to happen about nuclear power — about disaster un-preparedness in Japan. I wanted to contribute to that argument. It’s six years on and already we are airbrushing some things out.”

The book points out the gulf between rural Fukushima and the large cities consuming the energy it produced. Gilhooly talked to Atsufumi Yoshizawa, Yoshida’s deputy at the plant, who recalled the first home leave with his boss, a month after the disaster:

“Tokyo was … as though nothing had happened. They were selling things as usual, women were walking around with high heels and makeup as usual, while we didn’t even have our own clothes (which had been contaminated). I remember thinking, ‘What the hell is this? How can it be so different?’ I realized just how useless it would be to try and explain the situation at the plant to these people, what we had been through and the fear we had faced.”

It is a punch in the gut, then, to read about Yoshida’s death from esophageal cancer at age 58, just two years after his exposure to radiation. It’s one of the many elements of the Fukushima crisis that stirs anger, demanding a change that honors the lessons and sacrifice.

Gilhooly points out that, unlike Yoshida in the stricken plant, Japan has the chance to make positive choices about the future, choices that should be informed by the suffering in Fukushima.

“We should think more about how we use energy,” he concludes. “There are things we can do better, with small changes in lifestyle.” ”

by Nicolas Gattig, The Japan Times

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Near miss at Fukushima is a warning for U.S., panel says — Richard Stone, Science

” Japan’s chief cabinet secretary called it “the devil’s scenario.” Two weeks after the 11 March 2011 earthquake and tsunami devastated the Fukushima Daiichi Nuclear Power Plant, causing three nuclear reactors to melt down and release radioactive plumes, officials were bracing for even worse. They feared that spent fuel stored in the reactor halls would catch fire and send radioactive smoke across a much wider swath of eastern Japan, including Tokyo.

Thanks to a lucky break detailed in a report released today by the U.S. National Academies, Japan dodged that bullet. The near calamity “should serve as a wake-up call for the industry,” says Joseph Shepherd, a mechanical engineer at the California Institute of Technology in Pasadena who chaired the academy committee that produced the report. Spent fuel accumulating at U.S. nuclear reactor plants is also vulnerable, the report warns. A major spent fuel fire at a U.S. nuclear plant “could dwarf the horrific consequences of the Fukushima accident,” says Edwin Lyman, a physicist at the Union of Concerned Scientists, a nonprofit in Washington, D.C., who was not on the panel.

After spent fuel is removed from a reactor core, the fission products continue to decay radioactively, generating heat. Many nuclear plants, like Fukushima, store the fuel onsite at the bottom of deep pools for at least 5 years while it slowly cools. It is seriously vulnerable there, as the Fukushima accident demonstrated, and so the academy panel recommends that the U.S. Nuclear Regulatory Commission (NRC) and nuclear plant operators beef up systems for monitoring the pools and topping up water levels in case a facility is damaged. It also calls for more robust security measures after a disaster. “Disruptions create opportunities for malevolent acts,” Shepherd says.

At Fukushima, the earthquake and tsunami cut power to pumps that circulated coolant through the reactor cores and cooled water in the spent fuel pools. The pump failure led to the core meltdowns. In the pools, found in all six of Fukushima’s reactor halls, radioactive decay gradually heated the water. Of preeminent concern were the pools in reactor Units 1 through 4: Those buildings had sustained heavy damage on 11 March and in subsequent days, when explosions occurred in Units 1, 3, and 4.

The “devil’s scenario” nearly played out in Unit 4, where the reactor was shut down for maintenance. The entire reactor core—all 548 assemblies—was in the spent fuel pool, and was hotter than fuel in the other pools. When an explosion blew off Unit 4’s roof on 15 March, plant operators assumed the cause was hydrogen—and they feared it had come from fuel in the pool that had been exposed to air. They could not confirm that, because the blast had destroyed instrumentation for monitoring the pool. (Tokyo Electric Power Company, the plant operator, later suggested that the hydrogen that had exploded had come not from exposed spent fuel but from the melted reactor core in the adjacent Unit 3.) But the possibility that the fuel had been exposed was plausible and alarming enough for then-NRC Chairman Gregory Jaczko on 16 March to urge more extensive evacuations than the Japanese government had advised—beyond a 20-kilometer radius from the plant.

Later that day, however, concerns abated after a helicopter overflight captured video of sunlight glinting off water in the spent fuel pool. In fact, the crisis was worsening: The pool’s water was boiling away because of the hot fuel. As the level fell perilously close to the top of the fuel assemblies, something “fortuitous” happened, Shepherd says. As part of routine maintenance, workers had flooded Unit 4’s reactor well, where the core normally sits. Separating the well and the spent fuel pool is a gate through which fuel assemblies are transferred. The gate allowed water from the reactor well to leak into the spent fuel pool, partially refilling it. Without that leakage, the academy panel’s own modeling predicted that the tops of the fuel assemblies would have been exposed by early April; as the water continued to evaporate, the odds of the assemblies’ zirconium cladding catching fire would have skyrocketed. Only good fortune and makeshift measures to pump or spray water into all the spent fuel pools averted that disaster, the academy panel notes.

At U.S. nuclear plants, spent fuel is equally vulnerable. It is for the most part densely packed in pools, heightening the fire risk if cooling systems were to fail. NRC has estimated that a major fire in a U.S. spent fuel pool would displace, on average, 3.4 million people from an area larger than New Jersey. “We’re talking about trillion-dollar consequences,” says panelist Frank von Hippel, a nuclear security expert at Princeton University.

Besides developing better systems for monitoring the pools, the panel recommends that NRC take another look at the benefits of moving spent fuel to other storage as quickly as possible. Spent fuel can be shifted to concrete containers called dry casks as soon as it cools sufficiently, and the academy panel recommends that NRC “assess the risks and potential benefits of expedited transfer.” A wholesale transfer to dry casks at U.S. plants would cost roughly $4 billion. ”

by Richard Stone, Science

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Salt in the wound — Arnie Gundersen, Fairewinds Energy Education

” What really happened to the Fukushima Daiichi reactors when workers from owner Tokyo Electric Power Company added ocean saltwater to cool them?

Fairewinds recently received this question and important technical comments from several viewers and engineers regarding utility owner TEPCO’s use of saltwater to cool the Fukushima Daiichi atomic reactors during their triple meltdowns. As we continue looking at aging operating atomic reactors around the world, it is important to understand this issue and know what may go wrong at other sites.

Listen as Fairewinds’ Chief Engineer Arnie Gundersen explains why TEPCO’s workers injected saltwater into Fukushima’s failing reactors, what happens when salt water meets steel, and what forces come into play after saltwater is used to cool down an atomic reactor in this Fairewinds Audio Update. ”

source with audio and transcript