Japan’s government weighs dumping radioactive Fukushima water into the Pacific

As the cleanup of a triple meltdown following an earthquake and tsunami at the Fukushima nuclear power plant drags into its seventh year, one of the biggest continuing threats is less from airborne radioactivity than it is simple water.
 
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A waterlogged radiation and tsunami warning sign found on Fukushima beaches in 2013.
May 22, 2018
As the cleanup of a triple meltdown following an earthquake and tsunami at the Fukushima nuclear power plant drags into its seventh year, one of the biggest continuing threats is less from airborne radioactivity than it is simple water.
On March 11, 2011, the Fukushima plant was devastated by a tsunami, which over the ensuing days sent three of its six reactors into meltdown, while hydrogen explosions cast radioactive iodine, cesium and other fission by-products into the air. More than 160,000 people were forced to evacuated in the wake of the disaster, which has now become synonymous with Chernobyl.
At the time, officials began pumping millions of liters of water into the destroyed reactors to keep them cool, often dumping it from helicopters and spraying it through water cannons. In the years since, the water inundation has become less dramatic, but in the absence of any other way to keep the molten fuel cool, the flow of water continues to flow through the remains of the reactors at the rate of some 160 tons of water a day.
While much of that water undergoes purification to remove significant amounts of radiation, filters can’t cleanse the water of tritium, a radioactive isotope of hydrogen — a process likened by some scientists to separating water from water.
As a result, water contaminated with tritium is building up and space to store it at the disaster site is running out. Of the 1.13 million-ton water storage capacity that the plant has, some 1.7 million tons have been used up.
Cleanup workers have to build a new steel water tank at the rate of one every four days to contain it all, and space to build more is becoming scarce. According to Japan’s Ministry of Economy, Trade and Industry, the tanks already sprawl over an area that could accommodate 32 football fields. All of the storage, says the government, will run out by 2021.
This looming crisis has left the Japanese government and Tokyo Electric Power Company, which owns Fukushima,  pondering how to get rid of this water – a decision that is generating anxiety and scare headlines as an expert committee weighs whether or not to release the water into the Pacific Ocean.
Despite the national and worldwide case of nerves such a decision might provoke the Japanese government says it can do it without a threat to the country’s fishing industry. Tritium, after all, is a substance that naturally occurs in rivers and seabeds – even tap water. What’s problematic with the tritium at Fukushima, though, is that its levels in the Fukushima water are 10 times higher than Japanese national standards for dumping it.
Because of that, the government’s expert panel is considering several methods for the water’s disposal, including evaporating it, releasing it into the sea after electrolysis, burying it underground or injecting it deep into the geology.
But as cleanup costs continue to spiral, with some Japanese think tanks speculating the final bill could be as much as $470 billion to $660 billion,  releasing the water into the sea – after diluting it – may turn out to be the cheapest option.
It’s not the first battle against water that the cleanup effort has fought. As recently as two years ago, some 400 tons of ground water flowed into the facility daily. Tokyo Electric Power somewhat stemmed that by building an underground wall of frozen soil to staunch the seepage of radioactive water.
has managed to decrease the inflow by installing a 30-yard-long “ice wall” fence that freezing cold brine is pumped through to freeze the soil around it, reports Wired. The chilled soil is meant to create a barrier to keep additional groundwater from spilling into the radioactive area.
But this year, on the seventh anniversary of the disaster, an expert group commissioned by the Japanese government concluded that the subterranean wall is not entirely effective against the deluge, and that other methods of battling leakage have to be devised.
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Japan still at a loss in how to deal with Fukushima’s radioactive water

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20 May, 2018
The number of storage tanks for contaminated water and other materials has continuously increased at the Fukushima No. 1 nuclear power plant in Japan, and space for still more tanks is approaching the limit.
It is seven years since an eathquake and tsunami overwhelmed Fukushima and a way to get rid of treated water, or tritium water, has not been decided yet.
The Government and Tokyo Electric Power Company will have to make a tough decision on disposal of tritium water down the road.
At the Fukushima No. 1 nuclear plant, groundwater and other water enters the reactor buildings that suffered meltdowns, where the water becomes contaminated.
This produces about 160 tons of contaminated water per day. Purification devices remove many of the radioactive materials, but tritium – a radioactive isotope of hydrogen – cannot be removed for technical reasons. Thus, treated water that includes only tritium continues to increase.
Currently, the storage tanks have a capacity of about 1.13 million tons. About 1.07 million tons of that capacity is now in use, of which about 80 per cent is for such treated water.
Space for tanks, which has been made by razing forests and other means, amounts to about 230,000 sq m – equivalent to almost 32 football fields. There is almost no more available vacant space.
Efforts have been made to increase storage capacity by constructing bigger tanks when the time comes for replacing the current ones. But a senior official of the Economy, Trade and Industry Ministry said, “Operation of tanks is close to its capacity.”
TEPCO plans to secure 1.37 million tons of storage capacity by the end of 2020, but it has not yet decided on a plan for after 2021. Akira Ono, chief decommissioning officer of TEPCO, said, “It is impossible to continue to store [treated water] forever.”
Tritium exists in nature, such as in seas and rivers, and is also included in tap water. The ordinary operations of nuclear plants produce tritium as well.
Nuclear plants, both in Japan and overseas, have so far diluted it and released it into the sea or elsewhere. An average of 380 trillion becquerels had been annually released into the sea across Japan during the five years before the accident at the Fukushima No. 1 nuclear plant.
Bottles that contain the treated water continue to be brought one after another to a building for chemical analysis on the grounds of the Fukushima No. 1 nuclear plant. The tritium concentration of the treated water is up to more than 1 million becquerels per liter, which is more than 10 times higher than the national standard for release into the sea – 60,000 becquerels per liter. But if diluted, it can be released into the sea.
The industry ministry’s working group compiled a report in June 2016 that said that the method of release into the sea is the cheapest and quickest among five ideas it examined. The ideas were:
– release into the sea;
– release by evaporation;
– release after electrolysis;
– burial underground;
– injection into geological layers.
The committee plans to hold a public hearing in Fukushima Prefecture and other places to hear citizens’ opinions on methods of disposal.

Storage capacity for radioactive water at Fukushima power plant nears limit

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May 19, 2018
The number of storage tanks for contaminated water and other materials has continuously increased at Tokyo Electric Power Company Holdings, Inc.’s Fukushima No. 1 nuclear power plant, and space for still more tanks is approaching the limit.
 
Behind this is the fact that a way to get rid of treated water, or tritium water, has not been decided yet. The government and TEPCO will have to make a tough decision on disposal of tritium water down the road.
Water volume increasing
At the Fukushima No. 1 nuclear plant, groundwater and other water enters the reactor buildings that suffered meltdowns, where the water becomes contaminated. This produces about 160 tons of contaminated water per day. Purification devices remove many of the radioactive materials, but tritium — a radioactive isotope of hydrogen — cannot be removed for technical reasons. Thus, treated water that includes only tritium continues to increase.
 
Currently, the storage tanks have a capacity of about 1.13 million tons. About 1.07 million tons of that capacity is now in use, of which about 80 percent is for such treated water.
Space for tanks, which has been made by razing forests and other means, amounts to about 230,000 square meters — equivalent to almost 32 soccer fields. There is almost no more available vacant space.
Efforts have been made to increase storage capacity by constructing bigger tanks when the time comes for replacing the current ones. But a senior official of the Economy, Trade and Industry Ministry said, “Operation of tanks is close to its capacity.”
TEPCO plans to secure 1.37 million tons of storage capacity by the end of 2020, but it has not yet decided on a plan for after 2021. Akira Ono, chief decommissioning officer of TEPCO, said, “It is impossible to continue to store [treated water] forever.”
Sea release rated highly
Tritium exists in nature, such as in seas and rivers, and is also included in tap water. The ordinary operations of nuclear plants produce tritium as well. Nuclear plants, both in Japan and overseas, have so far diluted it and released it into the sea or elsewhere. An average of 380 trillion becquerels had been annually released into the sea across Japan during the five years before the accident at the Fukushima No. 1 nuclear plant.
Bottles that contain the treated water continue to be brought one after another to a building for chemical analysis on the grounds of the Fukushima No. 1 nuclear plant. The tritium concentration of the treated water is up to more than 1 million becquerels per liter, which is more than 10 times higher than the national standard for release into the sea — 60,000 becquerels per liter. But if diluted, it can be released into the sea.
Regarding disposal methods for the treated water, the industry ministry’s working group compiled a report in June 2016 that said that the method of release into the sea is the cheapest and quickest among five ideas it examined. The ideas were (1) release into the sea, (2) release by evaporation, (3) release after electrolysis, (4) burial underground and (5) injection into geological layers.
After that, the industry ministry also established an expert committee to look into measures against harmful misinformation. Although a year and a half has passed since the first meeting of the committee, it has not yet reached a conclusion.
At the eighth meeting of the committee held on Friday, various opinions were expressed. One expert said, “While the fishery industry [in Fukushima and other prefectures] is in the process of revival, should we dispose of [the treated water] now?” The other said, “In order to advance the decommissioning, the number of tanks should be decreased at an early date.”
The committee plans to hold a public hearing in Fukushima Prefecture and other places to hear citizens’ opinions on methods of disposal.

“When they called me a ‘germ’ I wanted to die”

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May 13, 2018
But Fukushima boy fought back, helping win a court victory that brought compensation for evacuees from the nuclear disaster
On October 25, 2017, 15-year old former Fukushima resident Natsuki Kusano (not his real name and he has asked not to be pictured) testified before the Tokyo District Court. He was among a number of Fukushima evacuees seeking compensation from Tepco and the Japanese government and asking the court to hold the company and the government responsible for the Fukushima nuclear disaster.
As reported by the Asahi Shimbun, on March 16, 2018, the  Tokyo District Court found the central government and TEPCO responsible for contributing to the psychological stress suffered by 42 evacuees and ordered the defendants to pay a total of about 60 million yen ($566,000) in compensation.
The lawsuit was filed by 47 individuals in 17 households who fled from Fukushima Prefecture to Tokyo in the wake of the nuclear disaster. Significantly, 46 of those individuals evacuated voluntarily from areas where no evacuation order was issued by the government.
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Natsuki’s mother (left) cries with joy when she hears the Tokyo court verdict.
When the verdict came down, Natsuki was in Geneva with his mother and other women who were there to urge the Japanese government to abide by the UN recommendation of a 1 millisievert per year radiation exposure level. The Japanese authorities had raised this level to an unacceptable 20 msv per year in order to justify ordering people to return to affected areas or risk losing their compensation.
This was the sixth ruling so far among at least 30 similar law suits filed in Japan.  Four rulings have held the central government liable for the nuclear disaster and ordered it to pay compensation.
The plaintiffs believe that Natsuki’s declaration played an important role in the victory. Here is what he said:
Life in Iwaki
I was born in Iwaki city, Fukushima. I lived there with my parents and my little brother who is younger than me by 5 years.
While we were in Iwaki, we enjoyed our life season by season. When spring came, we appreciated cherry blossoms at “the Night Forest Park”, which was famous for its marvelous row of cherry trees that lots of people also know about well through the TV. In summer we went gathering shellfish. We had a fun time hunting wild mushrooms in fall and made a snowman in winter.
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A treasured life was lost after being forced to evacuate from Fukushima.
In a park or on my way home from school, I picked a lot of tsukushi (stalks of field-horsetail). My mother simmered them in soy and made tsukudani, which we loved very much. We lived in a big house with a large garden where we grew blueberries, shiitake mushrooms and cherry tomatoes. At school I collected insects and made mud pies with my friends.
Life after the Accident
But we have lost these happy days after March 11,  2011. The Night Forest Park is located in the “difficult-to-return zone”. We can’t make pies with mud fully contaminated by radioactivity.  However, the worst of it was that I was bullied at a school I transferred to.
Some put cruel notes on my work in an art class, others called me a germ. These distressing days continued a long time and I began to wish to die if possible. Once when I was around 10 years old, I wrote on a wishing card on the Star Festival, “I want to go to Heaven.”
Perhaps those who have no way of knowing anything about evacuees see us as “cheating people”. They might think that the evacuees from Fukushima got great compensation and live in shelters in Tokyo for free with no damage at home.
I believe that these misunderstandings would not have happened if the government and TEPCO (Tokyo Electric Power Company) had told the truth about the horrible reality of radioactive contamination and had provided accurate information to the public: they have hardly paid any compensation to the extramural evacuees. (Note: these are the evacuees who fled from areas outside of the official evacuation zone. Because they left without the evacuation order, the government considers them “voluntary” evacuees who are therefore not entitled to compensation. In its verdict, the Tokyo district court recognized the rights of these self-evacuees.)
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Contrary to propaganda, Fukushima evacuees were no freeloaders
I have not revealed that I am an evacuee at my junior high school which has no relations with the former school, and actually I have not been bullied ever since.
What I wish adults to bear the blame for
It is adults who made the nuclear power plants. It is adults who profited from them. It is adults who caused the nuclear accident. But it is us children who are bullied, live with a fear of becoming sick and are forced apart from families.
After the accident, no one can say that a nuclear plant is safe anymore.
In fact, no one can say to me, “Don’t worry, you’ll never be sick.”
Nevertheless, the government and TEPCO say “Rest easy, trust us. Your home town is safe now,” and make us return to the place which is not safe.
I suspect that the adults who forced us to go back to the dangerous zone will be dead and not here when we are grown-up and become sick. Isn’t that terrible? We have to live with contaminants all through our life which adults caused. I am afraid that it is too selfish of them to die without any liability. While they are alive in this world, I strongly request them to take responsibility for what they did and what they polluted in return for their profits at least.
And now, please, please don’t force us go back to the contaminated place. We never ever want to do so. The nuclear accidents changed all the lives of the evacuees as well as mine, my parents’ and my brother’s. Who wanted this? None of us. The evacuees all agree that the government and TEPCO should take responsibility.
Court of justice, please listen to us children and all the evacuees.

Remediating Fukushima—“When everything goes to hell, you go back to basics”

5/11/2018
It may take 40 years for the site to appear like “a normal reactor at the end of its life.”
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A schematic of the Fukushima nuclear power plant hints at the complexity of decontamination and decommissioning operations.
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TEPCO workers survey operations at reactor buildings.
Seven years on from the Great East Japan Earthquake of March 2011, Fukushima Daiichi nuclear power plant has come a long way from the state it was reduced to. Once front and center in the global media as a catastrophe on par with Chernobyl, the plant stands today as the site of one of the world’s most complex and expensive engineering projects.
Beyond the earthquake itself, a well understood series of events and external factors contributed to the meltdown of three of Fukushima’s six reactors, an incident that has been characterized by nuclear authorities as the world’s second worst nuclear power accident only after Chernobyl. It’s a label that warrants context, given the scale, complexity, and expense of the decontamination and decommissioning of the plant.
How does a plant and its engineers move on from such devastation? The recovery initiatives have faced major challenges, constantly being confronted by issues involving radioactive contamination of everything from dust to groundwater. And those smaller issues ultimately complicate the remediation effort’s long-term goal: to locate and remove the nuclear fuel that was in the reactors.
A sense of scale
Jonathan Cobb, spokesperson for the World Nuclear Association, spoke with Ars about the scale of Fukushima, explaining that radioactive releases in Japan were much smaller than at Chernobyl, and the accident resulted in no loss of life from radiation: “Of course, this doesn’t take away from the enormous task currently being faced at Fukushima.”
 
The UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported in May 2013 that radiation exposure following the Fukushima accident didn’t cause any immediate health effects and that future health effects attributable to the accident among either the general public or the vast majority of workers are unlikely. A 2017 paper from UNSCEAR reports that these conclusions remain valid in light of continued research since the incident.
Even the most at-risk citizens, those living in Fukushima prefecture, are only expected to be exposed to around 10mSv as a result of the accident over their lifetimes. “For reference, the global average natural background radiation tends to be around 2.4mSv/year, but even 20mSv/year isn’t exceptional,” said Cobb.
Still, the accident was rated a 7 on the International Nuclear and Radiological Event Scale (INES), which is the highest rating possible, and designates it a Major Accident due to high radioactive releases. Estimates vary slightly, but Japan’s Nuclear Safety Commission report puts total releases at 570 petabecquerels (PBq) iodine-131 equivalent. (For comparison, Chernobyl released 5,200PBq iodine-131 equivalent.)
But the severity of the accident is probably most keenly felt in the scale of the cleanup. The incident has necessitated the ongoing cleanup and decommissioning of the plant—something that Tokyo Electric Power Company (TEPCO), the plant’s owner and operator, is responsible for. Even though the plant is seven years into the cleanup and has accomplished a great deal, we won’t see a conclusion for decades yet.
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Damage to reactor Units 1-4 in the aftermath of the March 2011 earthquake.
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In addition to damage to infrastructure and buildings, a large amount of wreckage was left strewn around the plant complex.
 

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Remotely operated machines were involved in clean-up of the most contaminated areas.
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A look inside the Primary Containment Vessel (PCV) of Unit 2.
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A composite image of photographs taken inside the Primary Containment Vessel (PCV) of Unit 2.
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A look at debris in the spent fuel pool of Unit 3.
Meltdowns and immediate priorities
Remarkably, seismic shocks of the magnitude 9 earthquake didn’t cause any significant damage to the earthquake-proofed reactors; rather, the tsunami knocked out power that precipitated reactor meltdowns in Units 1, 2, and 3. Subsequent explosions caused by hydrogen buildup (from zirconium cladding of fuel assemblies melting and oxidizing) in Units 1, 3, and 4 then expelled radioactive contamination, most of which fell within the confines of the plant.
Cobb explained that in the aftermath of this, the ongoing risk posed by radionuclides (notably, iodine-131 and cesium isotopes 134 and 137) depended on their half-lives. Iodine-131, with a half-life of just eight days, posed virtually no threat at all after just several months. It has been cesium-134, with a two-year half-life, and cesium-137, with a 30-year half-life, that have been the major focus of decontamination efforts. “Radioactive decay means that we’ve seen a reduction in contamination simply through time passing; at the plant, however, my expectation is that the majority of reduction has been due to efforts of TEPCO. Conditions have improved markedly and a sense of normalcy has returned.”
It’s useful to take stock of what TEPCO had to contend with from the outset. Lake Barrett, a veteran of the US nuclear energy industry who spent several years at the helm of decommissioning work at Three Mile Island reactor 2, is currently an independent special advisor to the Japanese Government and TEPCO board of directors. He told Ars, “When everything goes to hell on you, you go back to basics. You’re concerned with accident response and immediate recovery of the situation. Over the longer timeframe, the decontamination & decommissioning (D&D) focus shifts to a more deliberate approach to major technical challenges.”
Barrett explained that reactor stabilization at Fukushima—an imperative of the immediate recovery—has long since been achieved. Temperatures within the Reactor Pressure Vessels (RPVs) and Primary Containment Vessels (PCVs) of Units 1-3 are stable at between 15 to 30ºC, and there have been no significant changes in airborne radioactive materials released from reactor buildings. This qualifies as a ‘comprehensive cold shutdown’ condition.
Barrett explained how the issue of cooling is mostly non-existent at this point: “The three melted reactor cores emit less heat than a small car. Decay heat was a huge issue in the first weeks, but it’s no longer an issue. And while TEPCO still injects water onto the cores, this is more for dust suppression than anything else.”
With the reactors stable, early phases of TEPCO’s work simply involved debris clearing and restorative efforts throughout buildings and across the 3.5 square miles of the plant—both having been ravaged by the earthquake and tsunami. In the most contaminated places, remotely operated machines undertook most of the work. To reduce environmental contamination, they also removed top soils and vegetation, deforested the site, and then applied a polymer resin and concrete across much of the plant complex. This has locked contaminated material in place and limited the flow of groundwater through the site.
Other work has been more substantial. Units 1, 3 and 4 were blown apart and have had to be reinforced and encased, both for safety and to prevent spread of radioactive material. Although Unit 2 retained its roof, TEPCO decided to dismantle the upper building nonetheless, as it will facilitate removal of fuel from the reactor.
At the peak of these operations, some 7,450 persons worked at Fukushima. As operations have evolved, the workforce has declined to a not inconsiderable 5,000 daily personnel. With such levels of permanent staffing, it’s little wonder that a new rest-house, cafeteria, shops, and office building have all been built.
The efforts have, in a practical sense, meant that the majority of the site has transitioned to a stable, relatively risk-free environment. Describing the decommissioning as an “enormous challenge never before undertaken by humanity,” Seto Kohta of TEPCO told Ars: “We have overcome the state of chaos that ensued after the accident and have succeeded in reducing site dose levels to an average of less than 5μSv/h, with the exception of the vicinity of Units 1-4.” (Global background levels are <0.5µSv/h.)
TEPCO reports that the additional effective dose (i.e. additional to natural background radiation) at the plant’s boundary has declined to the target value of less than 1mSv/y.
This is not to say the plant is without signs of past problems—far from it. Felled trees sit waiting for incineration; huge mounds of soil lie under tarps; buildings retain marks of past trauma; and with environmental dosage a perennial concern, close to a hundred dose-rate monitors are positioned around the site.
Kohta also noted that while “95 percent of the site no longer requires the donning of full- or half-face masks or coveralls,” some level of protection is still required for working around the plant according to three levels of contamination. The vast majority of the plant grounds are in what’s termed Zone G, which requires just generic coveralls and disposable medical masks. Zone Y provides a perimeter around the Units 1-4 and necessitates heavier-duty coveralls and either full- or half-face masks. And lastly there is Zone R, closer to and including the reactor buildings, requiring double-layered coveralls and full-face masks.
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A steel structure is built around Unit 1 as part of reconstruction works.
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An outer shell is constructed around Unit 1.
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Reconstruction work at Unit 4.
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A labyrinth of subterranean tunnels and access points lie around reactor buildings.
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The Little Sunfish submersible used for investigations at Unit 3.
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A TEPCO schematic illustrates measures taken to manage groundwater.

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An impermeable wall constructed of interlocking columns extends along the seafront to restrict contaminated water reaching the sea.

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Above ground apparatus of the frozen wall which descends 30m and surrounds Units 1-4.

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A visitor to the plant performs a low-tech check on the frozen wall.

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The groundwater bypass pump works to reduce the amount of water leaking into the reactor buildings.
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Temporary storage tanks for water pumped up via the groundwater bypass.
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Flanged tanks of the sort used for indefinite storage of tritium-laced water arrive at the docks of Fukushima nuclear power plant.
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Visitors from IAEA visit the ALPS water treatment facility where radionuclides are removed from contaminated water.
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Defueling of the spent fuel pool at Unit 4 was performed in a conventional manner; it won’t be so easy at other Units where radiation and damage is more severe.
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The giant fuel handling machine (background) and fuel handling crane (foreground) arrive for installation at Unit 3.

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The final segment of the domed containment roof is lifted into place at Unit 3.
 
Reactor investigations
While they’re now stable in terms of nuclear activity, Units 1-3 remain highly contaminated. As such, while the structural integrity of these buildings has been restored, relatively little work has been undertaken within them. (One notable exception is removal of contaminated water from condensers, completed last year.)
Over recent years, a variety of remotely operated devices and imaging technologies have performed investigations of these units. The intention has been to gather information on internal physical and radiological conditions of the PCVs—the heavily reinforced bell-shaped structures that host reactors. TEPCO wants, and needs, to understand what has happened inside. Some things are known: once melted, fuel mixed with structural materials including steel and concrete to form something known as corium. But precisely where the corium ended up, how much there is, and whether it’s submerged are just some of the questions in play.
The International Research Institute for Nuclear Decommissioning (IRID), which was established in April 2013 to guide R&D of technologies required for reactor defueling and decommissioning, is supporting TEPCO in seeking answers. IRID is composed of multiple stakeholders, including Japanese utilities and the major nuclear vendors Hitachi, Mitsubishi, and Toshiba.
Naoaki Okuzumi, senior manager at IRID, described for Ars the investigative approaches and technologies. Early work utilized Muon tomography, which Okuzumi described as “a kind of standard practice applied to each unit… to locate high density material (fuel) within PCVs.” It yielded low-resolution data on the approximate location of corium. But with pixels representing 25cm-square cross-sections, the information has been useful only in so far as validating computational models and guiding subsequent robotic investigations.
The latter task hasn’t been easy. In addition to the challenge of navigating the dark, cramped labyrinths of tangled wreckage left behind, TEPCO has had to contend with radioactivity—the high levels act something like noise in electronic circuits. The wreckage has made access a challenge, too, although varying points of ingress have been established for each PCV.
The circumstances mean that TEPCO hasn’t been able to simply purchase an off-the-shelf kit for these investigations. ”An adaptive approach is required because the situation of each PCV is different… there is no standard with investigating the PCVs by using robots,” said Okuzumi, describing an approach that has translated into devices being specially developed and built in response to conditions of each PCV.
But they’re making progress. As recently as January 2018, corium was identified for the first time inside Unit 2 using an enhanced 13m-long telescopic probe and a revised approach designed to overcome problems encountered during investigations in 2017. The situation was hardly easier at Unit 3, where the PCV is flooded to a depth of around 6.5m. Here, it took a remotely operated, radiation-shielded submersible called ‘Little Sunfish’ to locate corium in July 2017.
Altogether the investigations—featuring a litany of robotic devices—have revealed that little fuel remains in any of the cores of Units 1-3. In Unit 2, a large amount of corium is present at the bottom of the RPV; in Units 1 and 3, almost all fuel appears to have melted through the RPVs entirely and into the concrete floor of PCVs beneath. The information is crucial, as we’ll come to see, for future deconstruction work at the reactors, but it continues to be extended as investigations continue.
 
PCV investigations at Unit 2
 
Pumps, ice-walls, and storage: Water management
One of TEPCO’s major concerns has been groundwater, which runs down from mountains west of the plant and can become contaminated by the low-lying reactors before flowing out to sea. Groundwater management has subsequently become one of TEPCO’s greatest efforts, as well as one of the most challenging of the tasks it has faced.
First off, it ought to be noted that marine environment monitoring for radionuclide concentrations near the plant and as far away as Tokyo indicate that levels are well within WHO standards. “The levels of radioactivity that have been found and can be attributed to Fukushima are absolutely dwarfed by natural levels of radioactivity in the water, or even levels of cesium that came from historic nuclear weapons testing,” noted Cobb.
Still, the effort to limit further contamination—seemingly driven as much by societal-political dynamics as safety considerations—remains paramount. To this end, measures have been deployed along three principles: remove sources of contamination, isolate water from contamination, and prevent leakage of contaminated water.
Some measures have been simple enough in design. Installation of an impermeable, underground wall along the sea front, completed in October 2015, is intended to keep groundwater that passes Units 1-4 from reaching the sea. Waterproofing pavement against rainwater is another widely applied step.
After this, solutions become more sophisticated. A groundwater bypass that intercepts and pumps up water before it reaches the reactors is a key development. This water is inspected for contamination before being discharged into the sea. By November 2017, more than 337,000 cubic meters of water had been released to the ocean in this way; this bypass reduced the amount flowing into the building basements by up to 100 tons per day and successfully reduced groundwater levels around the reactor buildings.
To further limit groundwater flow into reactors buildings, TEPCO actually froze the ground around them, creating a kind of frozen wall down to a depth of about 30 meters. Approximately 1,500 meters long, the wall is kept frozen by pipes filled with an aqueous solution of calcium chloride cooled to -30ºC. Freezing commenced in March 2016 and is now “99 percent complete,” according to Kohta.
On either side of the frozen wall, sub-drains and groundwater drains have been installed; they pump water up to keep it from reactor buildings and reaching the sea, respectively. Pumped water is purified at a purpose-built treatment facility. Barrett commented: “With water released from sub-drains and the bypass, there’s an agreement with the fishing industry that releases must be below 1,500 becquerels per liter. Negotiations took several years to agree that level was ‘clean’.”
All this has come at enormous expense, but according to TEPCO, it has been successful. Before any measures were implemented, inflow was around 400m3/day, Kohta told Ars. “The average amount of water flowing into [Units 1-4] for the period from December 2015 to February 2018, before the closure of the land-side impermeable wall, was 190m3/day, and it has decreased to 90m3/day after the closure for December 2017 to February 2018.”
At face value, it’s a sound outcome. As Kohta noted, the amount of contaminated water now being generated—a mix of groundwater, rainwater and water pumped into reactors for cooling—has decreased from about 520m3/day to about 140m3/day between last December and February. Even so, treating that amount of contaminated water is proving taxing.
Water treatment is happening at large-scale facilities that have been built onsite, including a multi-nuclide removal facility. Here, a so-called Advanced Liquid Processing System (ALPS) reduces concentrations of cesium isotopes, strontium, and other radionuclides to below legal limits for release. But one radionuclide remains: tritium.
Cobb explained: “The difficulty is that tritium is basically an isotope chemically identical to hydrogen, so it’s impractical to remove. Levels of tritium in that water are low, but nevertheless there’s great sensitivity to the suggestion that it be discharged.”
Without a feasible alternative for cleaning up the tritium, the (only) solution for ALPS-treated water has been storage. Well over a thousand tanks, each holding 1,200 cubic meters, now store tritium-laced water at the south end of the plant. Several years ago, these tanks hit the news because several were found to be leaking. Barrett acknowledged it as an unfortunate and avoidable incident resulting from use of flange-tanks. TEPCO has since moved to more sturdy welded-joint water storage tanks.
The ultimate plan for stored water is unknown; tritium has a half life of a dozen years, so physics won’t clean up the water for us. Some kind of controlled, monitored discharge—the likes of which is typical within the nuclear industry—is possible, according to Barrett. Indeed, the International Atomic Energy Agency has endorsed such a plan, which was proposed by the Atomic Energy Society of Japan in 2013. The plan involved diluting tritiated water with seawater before releasing it at the legal discharge concentration of 0.06MBq/L and monitoring to ensure that normal background tritium levels of 10Bq/L aren’t exceeded.
Discussions at both national and international levels would need to come first. Part of the difficulty here harkens back to societal dynamics surrounding risk and contamination: “In nuclear there is no such thing as absolute zero—sensitivity goes down to the atom. This makes discussion about decontamination or levels of acceptable contamination difficult. There’s tritium in that water that’s traceable to the accident; it’s entirely safe, but for the time being, with the event still in recent memory, it’s not acceptable,” observed Barrett.
Toward permanent solutions
In some sense, much of the restoration of order at Fukushima has been superficial—necessary but concerned with handling consequences more than root causes (see, TEPCO interactive timeline). Ultimately, Fukushima’s reactors must be decommissioned. Broadly, this work involves three phases: removing used fuel assemblies that are stored within ten-meter-deep spent fuel pools of each reactor building, management of melted-down reactors and removal of corium debris, and deconstruction of reactor buildings and the greater plant.
At Unit 4, spent fuel removal operations took around 13 months and concluded in December 2014. “When we began we didn’t know if fuel assemblies or racks were distorted. It turned out they weren’t, and we were able to remove all fuel conventionally without any issues at all. Actually, it went exceedingly well, concluding ahead of schedule and under cost,” recalled Barrett. In all, 1,533 fuel assemblies were removed and transferred to a common spent fuel pool onsite.
 
Spent fuel removal at Unit 4 was accomplished with conventional techniques.
 
Defueling of pools at Units 1 through 3, which suffered meltdowns, isn’t going to be as straightforward. For one, there’s some expectation of debris and circumstances requiring extraordinary removal procedures. “I wouldn’t be surprised if we find some structurally bent fuel assemblies caused by large pieces of concrete or steel,” said Barrett.
Additionally, although radiation in Unit 3 has been reduced sufficiently to allow rotating shifts of workers to install defueling equipment, the already painstaking operations will have to be conducted remotely. The same is likely true for Units 1 and 2.
At Unit 3, the next in line for defueling, preparation is already well underway. In addition to decontamination and installation of shielding plates, TEPCO has removed the original fuel handling crane, which had fallen into the pool seven years ago, and installed a new fuel handling crane and machine. An indication of extraordinary containment methods being used, workers have built a domed containment roof at Unit 3. TEPCO’s Kohta told Ars, “Removal of spent fuel [at Unit 3] is scheduled to begin from around the middle of 2018;” meanwhile, Unit 1 is also in a preparatory stage and Unit 2 will be handled last.
Further down the line still, corium will have to be removed from melted-down reactors. It’s a daunting task, the likes of which has never been undertaken before. The reactors held varying, but known, amounts of uranium oxide fuel, about 150 tonnes each. But how much extra mass the fuel collected as it melted through reactor vessels is uncertain.
“At TMI there was exactly 93 tonnes in the reactor. Once we were done digging out fuel debris, we’d removed 130 tonnes. At Fukushima, I expect maybe a factor of five to ten more mass in core debris. It’s an ugly, ugly mess underneath the PCVs,” suggested Barrett.
High-powered lasers, drills and core boring technologies for cutting, and strong robotic arms for grappling and removing corium are already under development, according to IRID, but precise methodologies remain undecided.
The original plan, Barrett explained, was to flood PCVs and work underwater—a conventional nuclear operations technique that affords protection from contamination. But this requires water-tight PCVs, something that cannot be practically achieved at Fukushima. Discussions also continue over whether a side or top-down entry would be best. “Altogether, we don’t have enough physical data about PCVs to commit to a final decision,” said Barrett, referring back to the need for continued PCV investigations. According to Kohta, fuel debris removal isn’t scheduled to commence before the end of 2021.
Without doubt, the road ahead of TEPCO is a long one, beset with challenges greater than those faced to date. The Mid- and Long-Term Roadmap—the Japanese state-curated document outlining the decommissioning of Fukushima—envisions operations stretching a full 30-40 years into the future. Some have suggested it’s an optimistic target, others say that the plan lacks details on key, long-term issues such as permanent solid-waste storage beyond the onsite repository currently being employed. Certainly it is the case that key decisions remain.
For his part, Barrett concluded: “I believe that the 40-year timeframe is reasonable for a scientifically based decommissioning; that’s to say, to reach a point similar to that of a normal reactor at the end of its life. That’s not reaching the point of a green field where you’d want to put a children’s school. Could it be a brown-field, industrial site, though? Yes it could. That’s a rational, reasonable end point.”
By all accounts, it is hard to gauge the costs for the Fukushima clean-up. Kohta told Ars that works completed to date have cost about 500.2 billion yen, or $4.7 billion—a tremendous sum, to be sure, but fractional compared to the estimate of 8 trillion yen ($74.6 billion) approved by the Japanese state last May for the complete decommissioning of Fukushima Daiichi.
 

Seismologist testifies Fukushima nuclear disaster preventable

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In this March 11, 2011 photo provided by Tokyo Electric Power Co., a tsunami is seen just after striking the Fukushima No. 1 nuclear plant breakwater.
 
May 10, 2018
TOKYO — A seismologist has testified during the trial of three former executives of Tokyo Electric Power Co. (TEPCO), operator of the tsunami-ravaged nuclear plant, that the nuclear crisis could have been prevented if proper countermeasures had been taken.
“If proper steps had been taken based on a long-term (tsunami) evaluation, the nuclear accident wouldn’t have occurred,” Kunihiko Shimazaki, professor emeritus at the University of Tokyo, told the Tokyo District Court on May 9.
Shimazaki, who played a leading role in working out the national government’s long-term evaluation, appeared at the 11th hearing of the three former TEPCO executives as a witness.
Prosecutors had initially not indicted the three former TEPCO executives. However, after a prosecution inquest panel consisting of members of the public deemed twice that the three deserve prosecution, court-appointed lawyers serving as prosecutors indicted the three under the Act on Committee for Inquest of Prosecution.
Court-appointed attorneys insist that former TEPCO Vice President Sakae Muto, 67, and others postponed implementing tsunami countermeasures based on the long-term evaluation, leading to the disaster.
The government’s Headquarters for Earthquake Research Promotion released its long-term evaluation in 2002 predicting that a massive tsunami could occur along the Japan Trench including the area off Fukushima.
In 2008, TEPCO estimated that a tsunami up to 15.7 meters high could hit the Fukushima No. 1 power station, but failed to reflect the prediction in its tsunami countermeasures at the power station.
The Cabinet Office’s Central Disaster Prevention Council also did not adopt the long-term evaluation in working out its disaster prevention plan.
Shimazaki, who was a member of the Headquarters for Earthquake Research Promotion’s earthquake research panel in 2002, told the court that the Cabinet Office pressured the panel shortly before the announcement of the long-term evaluation to state that the assessment is unreliable. The headquarters ended up reporting in the long-term evaluation’s introduction that there were problems with the assessment’s reliability and accuracy.
In his testimony, Shimazaki pointed out that the Central Disaster Prevention Council decision not to adopt the long-term evaluation led to inappropriate tsunami countermeasures.
With regard to factors behind the council’s refusal to accept the evaluation, Shimazaki stated that he can only think of consideration shown to those involved in the nuclear power industry and politics.
“If countermeasures had been in place based on the long-term evaluation, many lives would’ve been saved,” Shimazaki told the court.
Shimazaki served as deputy chairman of the government’s Nuclear Regulatory Authority after the Fukushima nuclear disaster.
(Japanese original by Epo Ishiyama, City News Department, and Ei Okada, Science & Environment News Department)

New Data for Unit 2’s Missing Fuel

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TEPCO published a Roadmap document right before leaving for Golden Week vacation. In this document is a 30+ page section of new data for unit 2’s missing fuel.
 
TEPCO has given varying explanations for unit 2’s meltdown and fuel location. Two muon scans have been completed for unit 2. The first found no fuel remaining in the RPV. A second scan by TEPCO claimed to have found some fuel in the bottom of the RPV, our analysis of the scan found otherwise. It is likely that all of the fuel inside the reactor vessel melted and all of it except for some residues is no longer in the RPV.
 
Fuel debris volume:
The volume of fuel debris inside unit 2 is difficult to calculate due to a number of factors. The debris is spread between multiple areas including the floor grate level, the pedestal floor and whatever debris may have burned down into the pedestal floor. The total volume of the fuel core is known for unit 2 but the exact size of the pedestal diameter is not known.
 
A fuel debris volume estimate was made for unit 1 based on known data and meltdown events at that reactor. Unit 1 is smaller than unit 2 in both fuel core size and size of the reactor structures. The general reactor building sizes and the fuel core sizes should be something that could roughly scale up for unit 2. Unit 1 estimate showed a fuel volume of all of the fuel and related melted structural materials as 60-100 cm deep.
 
Inside unit 2 about 50% of the pedestal floor was found to be covered with 70 cm of fuel debris. Additional fuel debris in an unknown volume is on the floor grate level. An unknown amount is burned down into the pedestal concrete basemat. Further fuel debris may be in lower reactor piping systems or the outer drywell floor. Unit 2’s fuel debris volume would also be reduced as the control rod drive array and bottom head of the reactor vessel are still intact. That large amount of metal structural material is known to not be part of the melted fuel debris in unit 2.
 
What has been found on inspection may be all of the fuel debris for unit 2 if a portion of the material is burned down into the pedestal basemat concrete. In most meltdown scenarios that is a given assumption unless the containment structure was heavily and repeatedly flooded with water at the time the fuel first dropped into the pedestal. With unit 2 that is an unlikely scenario.
 
There is an alternative possibility that a large amount of the radioactive materials in the fuel vaporized during the meltdown and escaped containment. This concept requires more investigation to confirm vaporization but this possibility for unit 2 is not completely ruled out. Fused microparticles containing nuclear fuel and other meltdown related materials have been found over a wide swath of Fukushima and beyond. Unit 2’s refueling floor blow out panel and reactor well containment gasket are one escape path for micro materials, steam and other gasses. Unit 2’s venting attempts are another concern. TEPCO has claimed the direct drywell venting of unit 2 didn’t work and the rupture disc for this system did not break as intended. TEPCO has provided no conclusive proof of this claim such as photos, video or other tangible evidence for this claim. Due to this, there is still the possibility that unit 2’s venting released some of these fused microparticles of fuel.
 
Radiation levels:
The radiation levels found in unit 2’s pedestal including a reading close to the fuel debris pile were between 7-8 Sieverts/hour. The high reading found along the CRD rail in 2017 was between 200-300 Sieverts/hour. These pedestal readings are drastically lower than what would be expected near an unshielded large pile of fuel debris.
By comparison, radiation levels along the outer containment wall in 2012 were within a similar range of the lower readings found on the CRD rail in 2017.
 
The elephant’s foot at Chernobyl, measured within the first year of the disaster, converted to Sieverts was 100 Sievert/hour.
 
Underwater readings in unit 1’s torus room near what is suspected fuel debris, taken in 2012 were 100,000 to 1 million Sieverts/hour.
 
Radiation levels near the fuel debris indicate that the top layers of debris may be mostly metallic materials with little fuel.
 
Radiation levels indicate that fuel bearing debris is not in the visible layer in the pedestal. (other possible locations – vaporized/vented, beneath the metallic layer, sml amounts in piping).