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Meet the robots looking for fuel after Fukushima’s Daiichi nuclear disaster

 

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November 20, 2018
Chernobyl remains the world’s worst nuclear disaster in terms of lives lost, but the worst radioactive mess the world has ever dealt with is in Fukushima, Japan. Seven years after the most powerful earthquake ever recorded in Japan led to a massive meltdown in the Daiichi Power Plant, Lesley Stahl reports on a clean-up effort that looks like a science fiction film. Her story on how one-of-a-kind robots are being designed for the decades-long task will be broadcast on 60 Minutes, Sunday, Nov. 25 at 7:30 p.m. ET and 7 p.m. PT on CBS.
The earthquake struck March 11, 2011, causing several huge tsunami waves that swamped Daiichi, cutting power to the seaside facility’s cooling pumps. Three reactors melted down, creating up to 3,000 tons of deadly radioactive fuel and debris that lays in the plant’s ruins. Finding it and containing it safely will be a historic task says nuclear engineer Lake Barrett. “This is a unique situation here. It’s never happened in human history. It’s a challenge we’ve never had before,” he tells Stahl. Barrett oversaw the cleanup of the Three Mile Island partial meltdown in 1979, the worst nuclear accident at a power plant in the U.S. He is also a consultant on the Daiichi project.
Daiichi can’t be encased in concrete, like Chernobyl, says Barrett, because the potential for another earthquake or tsunami that could compromise the structure is too high. Humans can’t get near the material; it will remain deadly for thousands of years. Authorities hope specially designed robots will find, remove and secure the toxic material in special containment vessels. But it could take 50 years and cost an estimated $200 billion.
There are four-legged robots, some that climb stairs and even robots that can swim into reactors flooded with water. They’re equipped with 3-D scanners, sensors and cameras that map the terrain, measure radiation levels and look for the deadly material.
The Japanese government set up a research facility nearby to develop and test the robots. Some have been deployed in what amounts to experimentation at this early stage, says Barrett. One robot is called the Scorpion for its ability to raise its camera-carrying tail. It struck debris and became stuck only ten feet into its $100 million mission. Says Barrett, “You learn more from failure sometimes than you do from success.”
Other early versions of robots died quick deaths, too, their cameras and operating systems fried by the intense radiation. It’s a slow and steady project, says Barrett, that he is confident will get done, but not in his lifetime, nor those of many others involved. The task has been compared to putting a man on the Moon. “It’s even a bigger project in my view. But there’s a will here to clean this up as there was a will to put a man on the moon,” says Barrett.
https://www.cbsnews.com/news/meet-the-robots-looking-for-fuel-after-fukushima-daiichi-nuclear-disaster-60-minutes/?fbclid=IwAR2HOYGGI3CPHy9OfjkruiMPvck4aPS32uRj4wwlIkLXlR1pywR6gJf8ryo

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November 25, 2018 Posted by | Fukushima 2018 | , | Leave a comment

NEDO, Fukushima Pref. Sign Cooperation Pact on Robot Tests

“To revitalize Fukushima Prefecture”, signing of a technological cooperation agreement with NEDO (organization for the development of new energies and industrial technologies), for tests of drones and robots ; construction of a huge site of 50 hectares straddling the municipalities of Minamisoma and Namie …

 

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Koriyama, Fukushima Pref., Nov. 22 (Jiji Press)–The New Energy and Industrial Technology Development Organization on Wednesday concluded a cooperation pact with the Fukushima prefectural government on the development of technologies for demonstration tests for drones and robots.
The organization, better known as NEDO, aims to establish technologies to accurately measure the durability and safety of drones and robots, utilizing the Fukushima Robot Test Field, a planned large test site over 50 hectares that straddles the city of Minamisoma and the town of Namie in a coastal region in the northeastern Japan prefecture.
The Fukushima government is building the site as part of efforts to revitalize the coastal region, devastated by the March 2011 earthquake and tsunami and the subsequent nuclear accident at Tokyo Electric Power Company Holdings Inc.’s <9501> Fukushima No. 1 power plant. The test site will partly enter into service in fiscal 2018.
Various demonstration tests will be conducted there, such as one to check a robot’s capabilities to conduct underwater inspections of old dams using a 7-meter-deep pool.
NEDO plans to develop technology to check whether drones can fly stably in strong wind. For this, the central government-linked organization will use a wind tunnel facility to be set up in the site.
 

November 25, 2017 Posted by | Japan | , , , , | Leave a comment

Muscle robots’ being developed to remove debris from Fukushima reactors

Hitachi-GE testing variety of simply structured, radiation-resistant equipment

20170818_Fukushima-reactor_article_main_image.jpgThe Unit 1 reactor building at the Fukushima Dai-ichi nuclear power plant of the Tokyo Electric Power Co. (TEPCO) in Okuma town, Fukushima prefecture, June 21, 2017.

 

TOKYO — A joint venture between Japanese and American high-technology power houses Hitachi and General Electric is developing special robots for removing nuclear debris from the Fukushima Daiichi nuclear power plant, the most difficult task in decommissioning the plant’s six reactors, three of which suffered core meltdowns in the March 2011 accident.

The machines under development by Hitachi-GE Nuclear Energy are called “muscle robots,” as their hydraulic springs operate like human muscles. The company, based in Hitachi, Ibaraki Prefecture, is stepping up efforts to complete the development project in time for the start of debris removal in 2021.

Hitachi-GE is testing the arms of the robots at a plant of Chugai Technos, a Hiroshima-based engineering service company, located a 30-minute drive from the center of the city. The testing is taking place in a structure with a life-size model of the primary containment vessel of the No. 1 reactor at the Fukushima plant. The robots awkwardly move about, picking up concrete lumps standing in for fuel debris.

“The robots are based on a concept completely different from those of conventional robots,” said Koichi Kurosawa, a senior Hitachi-GE engineer heading the development project. Hydraulics are being used because electronics cannot survive in the extreme environment inside the reactors.

“Asked if the robots are applicable to other nuclear power plants, I would say the possibility is low,” Kurosawa said, noting that the robots are designed to work amid intense radiation.

New challenges

While Hitachi-GE has built many nuclear reactors, it is encountering a variety of new challenges in developing the muscle robots simply because of the tough work required to retrieve fuel debris.

In the nuclear accident caused by the March 2011 earthquake and tsunami, cooling the fuel rods became impossible, and melted uranium fuel dropped from them. Some of the fuel broke through nuclear reactor pressure vessels and solidified as fuel debris containing uranium and plutonium.

The debris is estimated to weigh more than 800 tons in total. The insides of the PCVs at the Fukushima plant are directly exposed to the debris and are emitting radioactivity strong enough to kill a human within a few minutes.

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The International Research Institute for Nuclear Decommissioning, a Tokyo-based research institute for decommissioning nuclear plants, and three reactor makers — Hitachi-GE, Toshiba and Mitsubishi Heavy Industries — have been attempting to ascertain conditions inside the reactor buildings at the Fukushima plant by means of camera- and dosimeter-equipped equipment.

https://asia.nikkei.com/Tech-Science/Science/Muscle-robots-being-developed-to-remove-debris-from-Fukushima-reactors

September 2, 2017 Posted by | Fukushima 2017 | , , | Leave a comment

Robots expected to play key role in Fukushima decommissioning, but challenges remain

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As decommissioning work at Tokyo Electric Power Co. (TEPCO)’s Fukushima No. 1 Nuclear Power Plant continues, remote control robots are expected to play an important role in the decommissioning process. However, it is impossible to ignore the fact that the development of these robots faces huge challenges, such as high levels of radiation within the nuclear reactors, as well as a lack of information.

Among the robots that have been designed to carry out decommissioning work is the “muscle robot.” Developed by Hitachi-GE Nuclear Energy, Ltd., the body and limbs of the muscle robot can be controlled with a device that one might typically find attached to a video game console. Another type of robot acts like a crab with claws that can be used to grasp metallic pipes and snap them using a blade positioned on one of its claws. These robots are also able to smash concrete, using a special drill that can be placed at the end of the arm — like something out of a Hollywood movie.

Looking ahead, the government and TEPCO are aiming to start removing the melted nuclear fuel inside the No. 1 to No. 3 reactors at the Fukushima No. 1 nuclear plant in 2021, after announcing exactly how they plan to do so over the summer. Although knowledge regarding the matter is limited, it seems that the melted nuclear fuel in the reactors has cooled and solidified, and the prototypes of the robots have been produced based on the assumption that the devices need to break down and remove such hardened fuel.

The robots’ parts are connected together with springs, and are driven using hydraulic power. One of the main advantages of this system is that they are hardly affected by radiation. There are six types of robot in total, such as the “spider-style” robot which has six arms and legs (length 2.8 meters, width 2 meters, weight 50 kilograms), as well as a “tank-style” robot (length 4.35 meters, width 63 centimeters, weight 700 kilograms), which runs on a conveyor belt. The tank-style robot is capable of lifting objects weighing up to 50 kilograms. A representative from Hitachi-GE Nuclear Energy states determinedly, “I want the muscle robots to remove the melted nuclear fuel.”

However, the process will not be plain sailing. While the bodies of these robots are resistant to radiation, their cameras are somewhat vulnerable. It has been found that the electronic hardware in the cameras breaks easily after being exposed to radiation. For example, when a “cleaning robot” was sent into the No. 2 reactor on Feb. 9, 2017, the camera broke after about two hours after being exposed up to an estimated 650 sieverts per hour of radiation. The camera part of the robot is essential because without it, images cannot be transmitted back to the control room.

To solve this problem, ideas such as placing a metallic plate near the camera that would block out radiation have been discussed, but it is feared that this would make the robot heavier and interfere with its operations. As a Hitachi representative states, “If one were to use an analogy to describe the current development stage in human terms, then we have entered elementary school. We’d like to continue our work, believing we can develop usable robots.” It is clear that a trial-and-error process is very much underway, as the robot developers try their best to achieve perfection.

It will not be an easy road though. Hajime Asama, professor at the University of Tokyo and a member of the Technology Advisory Committee of the International Research Institute for Nuclear Decommissioning (IRID), states, “Robots are usually developed based on confirmation of what exactly lies in the reactors. However, in the case of the No. 1 power plant, no matter how hard you try to predict what is in there, there are often unexpected elements waiting.”

In the No. 2 reactor, a “scorpion-style robot” was sent in on Feb. 16, as a follow-up to the cleaning robot but it got trapped by deposits on the conveyor belt, and came to a halt. The presence of these kinds of deposits was unexpected at the stage when the robot was being designed. Too much is still unknown about the situation inside the reactors, making robot design difficult. Later this month, a “wakasagi ice fishing-type robot” is expected to be placed inside the No. 1 reactor, but it is feared that the same problems that were experienced in the No. 2 reactor will emerge once again.

In recent years, the use of artificial intelligence has been expected to play a key role but a number of unexpected problems have made progress in this area difficult. What is needed is technology that can be controlled remotely by people with flexible judgment. However, professor Asama believes that, “The reactors inside the No. 1 plant are full of unknown challenges. We have no choice but to use our available knowledge to create robots that can deal with these problems.”

https://mainichi.jp/english/articles/20170408/p2a/00m/0na/023000c

April 9, 2017 Posted by | Fukushima 2017 | , , | Leave a comment

Robots Go Into The Fukushima Nuclear Plant Site, But Don’t Come Out

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In 2011, a 9.0 magnitude earthquake off the coast of Japan caused a massive tsunami, which in turn led to the meltdown of three nuclear reactors at the Fukushima Nuclear Power Plant in Fukushima, Japan. As a result, the site went on to release radioactive material for the next three days, becoming only the second such disaster in history–after Chernobyl in 1986–to be classified a Level 7 event on the Nuclear Event Scale.

So perhaps it should come as no surprise that, just past the tragedy’s six year anniversary, Tokyo Electric Power Co. (Tepco) has made little progress in cleaning up the disaster site. 

While Tepco has spent much of its time containing radiation and attempting to minimize groundwater contamination, its current mission is to locate and retrieve 600 tons of melted nuclear fuel rods lost somewhere in the radioactive wreckage. As the levels of radiation are still too high for human exposure, this task has fallen to robots. Yet so far, even the robots have failed repeatedly to locate the melted fuel rods; instead, they are dying within the reactors they were sent in to survey. 

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The latest device to meet its end was a scorpion-shaped robot built by Toshiba, which entered one of the reactors last month but stalled just 10 feet short of its target in a matter of hours. While it was ultimately undone by the failure of its left roller-belt, the robot was exposed to far higher than expected levels of radiation, which likely interfered with its electronics and prevented it from sending photos that could have shed some light on the location of the melted fuel rods.

Despite being manufactured using special radiation-hardened materials to protect its circuits from exposure, the levels of radiation it encountered within the reactor far exceeded the robot’s tolerance. Two prior robot missions had to be aborted as well after one got stuck and another failed to locate any melted fuel for several days.

Despite the setbacks, Tepco believes it is getting closer to locating the melted fuel, and hopes to begin removal by 2021, but admits it is a long-term project. The Japanese government estimates that it will take upwards of 40 years and $70.6 billion to complete the clean-up.

According to MIT nuclear science professor Jacopo Buongiorno, “the roadmap for removing the fuel is going to be long, 2020 and beyond. The re-solidified fuel is likely stuck to the vessel wall and vessel internal structures. So the debris have to be cut, scooped, put into a sealed and shielded container and then extracted from the containment vessel. All done by robots.”

But that begs the question: what robots? 

None of those they’ve sent in so far has done the trick. What if the technology required to create the chips and robots that are radiation-hardened yet not too weighed down by protective shielding hasn’t even been invented yet? Bloomberg reports that Toshiba intends to send a new robot into Reactor 3 next year at this time to continue the search, but it is still in the development phase, and Toshiba has not yet made design details public.

The good news is that with a 40 year time horizon, the likelihood of technology catching up with Tepco’s needs is fairly good. But when will the site be clean enough so that more people may return to their homes? In the meantime, radioactive boars have been making themselves quite at home there.

http://secondnexus.com/technology-and-innovation/fukushima-robots-keep-dying/

March 21, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment

Radiation Spikes At Fukushima

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Juan Carlos Lentijo of the International Atomic Energy Agency looks at tanks holding contaminated water and the Unit 4 and Unit 3 reactor buildings during a February 2015 tour of the tsunami-stricken Fukushima Daiichi nuclear power plant.

Almost six years after a tsunami caused a meltdown at the Fukushima Daiichi Nuclear Power Plant, the facility’s operator, Tokyo Electric Power (Tepco) faces overwhelming problems to clean up the site. Tepco now reports radiation in reactor 2 that would kill a worker in thirty seconds, and even destroys robots. Arjun Makhijani, the President of the Institute for Energy and Environmental Research and host Steve Curwood discuss the implications of this new report and the challenges of cleanup.

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Arjun Makhijani is the President of the Institute for Energy and Environmental Research.

Transcript

CURWOOD: It’s Living on Earth, I’m Steve Curwood.

Six years after an earthquake and resulting tsunami devastated Fukushima, Japan and led to the meltdown of three nuclear power reactors there on the coast, radiation levels have reached a staggering 530 sieverts an hour, many times higher than any previous reading. Tepco, the plant’s operator, claims that radiation is not leaking outside reactor number two, site of these readings, but concedes there’s a hole in the grating beneath the vessel that contains melted radioactive fuel.

Joining us now to explain what it all means is Arjun Makhijani, President of the Institute for Energy and Environmental Research. Welcome back to Living on Earth Arjun.

MAKHIJANI: Thank you, Steve. Glad to be back.

CURWOOD: So, this report from TEPCO seems serious, maybe even ominous. What what exactly is going on?

MAKHIJANI: Well, they are exploring the molten core of the reactor in reactor number two with robots, and the robot called Scorpion went farther into the bottom of the reactor in an area called “the pedestal” on which the reactor kind of sits and measured much higher levels of radiation than before. The highest level was 73 Sieverts per hour before and this time they measured a radiation level more than seven times higher. It doesn’t mean it’s going up. It just was in a new area of the molten core that had not been measured before.

CURWOOD: Still, it sounds to me like it’s problematic, that six years after this meltdown there’s such a high reading.

MAKHIJANI: It is a very high reading; they may encounter even higher readings. The difficulty with this high reading is that the prospect that workers can actually go there, even all suited up, becomes more and more remote. Robots are going to have to do all this work – That was mostly foreseen – but the radiation levels are so high that even robots cannot survive for very long. So now they’re going to have to go back to the drawing board and redesign robots that can survive longer or figure out how to do the work faster, and it’s going to be more costly and more complicated to decommission the site.

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The lid of Unit 4’s Primary Containment Vessel lies close to the reactor building. The reactor was shut down for maintenance at the time of the accident.

CURWOOD: Remind us, Arjun, please, of the human impact of this kind of radiation. What’s toxic to humans?

MAKHIJANI: Right. So, if you get high levels of radiation in a short period of time, four Sieverts is a lethal dose for about half the people within two months. So, in 530 Sieverts per hour would give you a lethal dose in less than 30 seconds.

CURWOOD: Wow.

MAKHIJANI: So, it’s a very, very, very high level of radiation. That’s why people cannot go into the reactor and work there. That’s not the end of the bad news, but that’s quite a bit of it.

CURWOOD: OK. All right, there is more bad news. I’m sitting down. Tell me.

MAKHIJANI: Yes, so the bottom of the reactor under the reactor there is a grating and then under the grating there’s the concrete floor, and what this robot discovered — It was supposed to go around the grating and survey the whole area, but it couldn’t because a piece of the grating was deformed and broken. So, now it appears that some of the molten fuel may have gone through the grating and maybe onto the concrete floor. We don’t know because even robotic surveys are now difficult, and a high radiation turns into heat, so the whole environment around the molten fuel is thermally very hot, and so whether it is going through the concrete, whether it is under the concrete, I don’t know that we have a good grip on that issue.

CURWOOD: So, Arjun, what’s going on with the reactors one and three? There have been published reports that TEPCO, Tokyo Electric Power Company that has these reactors, hasn’t really taken a good look at those reactors. What do you know?

MAKHIJANI: Well, they have to develop the robots, and I think that developing them, by looking at reactor two, and they’re finding these surprises, radiation levels much higher than previously measured. It shouldn’t actually be unanticipated. The big surprise here was that a part of the grating was gone, and so that the molten fuel would possibly have gone through the grating. So, I think similar surprises will await reactors one and three because each meltdown will have a different geometry.

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Storing contaminated water in tanks at the Fukushima Daiichi site presents an ongoing risk, says Makhijani.

URWOOD: So, now what about the decay products here? We’re starting with the Uranium family, but we wind up with Cesium and Strontium – Strontium 90. What risk is there of Strontium 90 getting into groundwater there?

MAKHIJANI: Yeah, so the peculiar thing about a nuclear reaction is the initial fuel, Uranium, is not very radioactive. It’s radioactive but you can hold the uranium fuel pellets in your hand without getting a high dose of radiation. After it’s gone through the nuclear reaction – Fission, that’s what generates the energy – the fission products which result from splitting the Uranium atom are much more radioactive than Uranium, and Strontium 90 and Cesium 137 are two of the products that last for quite a long time, half-life 30 years, and are quite toxic. So, Strontium 90 is specially a problem when it comes in to contact with water. It’s mobilized by water. It behaves like calcium, so if it gets into like sea water and get into the fish, the bones of the fish, or human beings, of course, it gets into the bone marrow and bone surface, increases the risk of cancer, leukemia. So it’s a pretty nasty substance, and Strontium 90 has been contacted with water. You know, rainwater goes and contacts the molten fuel. Groundwater may be contacting the molten fuel. So, we have had Strontium 90 contamination and discharges into the ocean. They also collect the water. They’ve got about more than 1,000 tanks of contaminated water stored at the Fukushima site. By my rough estimate may be about 100 million gallons of contaminated water is being stored there.

CURWOOD: What happens if there’s an earthquake?

MAKHIJANI: That’s exactly right. So about a week into the accident, I sent a suggestion to the Japan Atomic Energy Commission that they should buy a supertanker, put the contaminated water into the supertanker, and send it off elsewhere for processing. They do have a site in the north of Japan which was supposed to be for plutonium separation, but it could be used to support the cleanup of Fukushima. But they rejected that proposal more than once and decided to build these tanks instead. They have a decontamination process on-site, and there are a very vast number of plastic bags on the site filled with contaminated soil. Nobody wants the stuff and nobody knows what’s going to happen with it.

CURWOOD: It’s six years after the original meltdown. How much of a disaster is Fukushima today?

MAKHIJANI: Well, Fukushima is possibly the longest running, continuous industrial disaster in history. It has not stopped because the risks are still there. This is going to take decades to decommission the site, and then what is going to happen with all this highly radioactive waste, ‘specially the molten fuel? Nobody knows.

CURWOOD: Arjun Makhijani is President of the Institute for Energy and Environmental Research. Thanks for taking time with us today, Arjun.

MAKHIJANI: So good to be back with you, Steve.

http://www.loe.org/shows/segments.html?programID=17-P13-00007&segmentID=6

March 10, 2017 Posted by | Fukushima continuing | , , , , | Leave a comment

Six years on, Fukushima rests its hopes on fearless robots

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As the struggle continues to bring the six-year-old triple nuclear meltdown at Fukushima Daiichi under control, robots are providing a first, albeit expendable, line of assault.

The robots are on a high-tech suicide mission into the nooks and crannies beneath the stricken plant’s three melted-down reactor cores to discover and map an estimated yet elusive 600 tons of molten nuclear fuel.

Radiation levels in these corridors can reach up to 650 sieverts and hour, higher by nine times than the previous highs measured at the plant, which plateaued at a mere 73 sieverts in 2012.

A whole human body dose of 10 sieverts is enough to cause immediate illness and death within a few weeks at most, 650 within a minute.

Levels like those recently found in the snarls and wreckage beneath Fukushima’s reactor No 2, where radiation is more concentrated because, unlike reactor No 1 and 3, it didn’t suffer a hydrogen explosion, are lethal not just to humans but, as it turns out, to robots as well.

The most recent robot that Tokyo Electric Power Co., the owner of the Fukushima plant, sent into the breach of reactor No 2 died in less than a day. The two before that got stuck in narrow passages and were given up for dead, and a third was abandoned after it spent six days searching for the reactor’s melted fuel. Yet one more robot was sacrificed in action while trying to locate one of its lost compatriots.

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Scientists are trying to develop robots better suited to the high radiation intensity. Yet they say the metallic body count is producing results by giving technicians a view of where the melted down fuel is located and helping them produce 3-D models of what it looks like.

The hope is that robots will be doing the heavy lifting when it comes time to dig out the fuel on a decommissioning job now expected to last another 30 to 40 years at a new cost of $189 billion – nearly double estimates released three years ago.

But on behalf of the 6,000 human workers at the site: Better the robots than them.

Six years ago, on March 11, 2011 a 9.0 magnitude earthquake 72 kilometers out to sea slammed a 39-meter tsunami into the Fukushima Daiichi nuclear power plant, causing a triple meltdown. In the days that followed, uranium fuel melted down in three of the six reactors. Explosions in three of the reactor buildings belched radioactive iodine, cesium and other fission by-products into the environment.

In the immediate aftermath, Japan shut down its 42 remaining nuclear reactors. Up to 160,000 people who lived within a 20-kilometer radius of the plant were forced to evacuate homes where they had lived for generations with their families in agricultural Fukushima.

Six years later, the lemming-like march of robots into the still chaotic cleanup of the plant has become a hopeful metaphor for technology accomplishing what is beyond humanity’s grasp, and their deaths are getting a lot of attention.

Tepco is still hewing to its vow of securing the plant by 2050 to 2060, and says that for the first time since the accident it has succeeded in reeling in the threat the wrecked plant poses to the surrounding area. A visual example of that, noted by reporters who took their annual tour of the plant, is that the thousands of workers on site can now work in ordinary work clothes and surgical masks rather than protective gear. And there are fewer workers to count. Where 8,000 were working at the site last year, 2000 fewer are needed now.

Damaged reactor buildings have been reinforced and 1,300 precariously perched spent fuel assemblies at reactor No. 4 that were a potential disaster all their own have been safely removed. The ground has also been covered with a special coating to prevent rainwater from added to Tepco’s water management struggles.

The company’s projection that it will finish the cleanup in the next four decades, however, is viewed skeptically by Japan’s Nuclear Regulatory Authority, which recently told the Guardian newspaper that the effort was still groping in the dark. And many are suspicious that the Tepco’s optimism is just public relations to assure the international community ahead of the 2020 Tokyo Olympics.

Can you go home again?

Another looming nightmare for many thousands of people is the prospect of loosing government financial support if they don’t move back to villages and towns they evacuated, which many environmental groups say are still highly contaminated.

The evacuation orders enacted by Prime Minister Shinzo Abe’s government after the disaster will be stripped later this month, forcing the evacuees back to live in areas that where in the direct path of the disaster.

Abe’s government says it’s safe for people to return to areas where radiation is 20 millisieverts per year or lower. The globally-accepted limit for radiation absorption is 1 millisievert per year, though the IAEA says anything up to 20 millisieverts per year poses no immediate danger to humans. That has been disputed by numerous studies.

Water hazards

At the plant, contaminated water still poses one of the biggest threats to the wider environment. Nearly one million tons of it stored across 1,000 tanks that were collected after the reactors were blasted with seawater to cool them down. More water has poured in as technicians continue to circulate it through the destroyed reactors to keep them cool.

Leaks from these tanks have often contaminated groundwater, and Tepco has struggled to divert the radioactive deluge from spilling into the Pacific Ocean with an underground wall of frozen soil.

The wall looks a bit like the piping behind a refrigerator and sinks 30 meters into the ground. Over the last year, Tepco pumped water into it to begin the freezing process. But some reports say the wall is having less success in another of its tasks – holding back groundwater from leaking into the basements of reactor buildings, which creates yet more contaminated water.

At their six-year anniversary briefing to reporters, Tepco admitted it was conflicted over what to do with the sea it has amassed. The company says it will be able to cleanse much of the water of cesium, strontium and 50 other radionuclides. But they’re still stumped by how to get rid of tritium, a radioactive isotope of hydrogen, which is still in that water.

Tepco is studying two options. One is to simply dilute the water further and dump it into the sea, as tritium naturally occurs in water in microscopic quantities. They’re also considering evaporating all 960,000 tons of it to release the tritium into the atmosphere.

The company says the final decision will be subject to a public hearing process. Should dumping water into the sea – as has happened numerous times before – still be among the considerations, it would doubtless meet the fierce opposition of fishermen, who have struggled with contaminated seawater since the accident.

Robots’ maze hunt

But by far the most technically involved struggle is finding and removing the fuel that melted down in reactor Nos 1, 2 and 3. And for that, enter the robots, each of which has to be shaped to its task.

At reactor No. 2, where the robot crews have been doing most of their work, it’s not yet known if the fuel melted into or through the reactor vessel’s concrete floor. Determining where that fuel is, and how radioactive it is, dictates how the robots will be designed.

And that’s just for this reactor. At reactor Nos 1 and 3, robots will have to be further customized to handle the specifics of each location. With explorations underway at reactor No 2, Tepco says it expects more robots to march into the other reactors by this summer.

At that point, they say, they will set policy on how the melted fuel will be removed, a process that isn’t expect to begin until 2021.

Designing and building what Tepco refers to as “single function robots” takes as long as two years, and that’s only when you know what you are making the robots for.

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One of the robots currently on the drawing board, for instance, would be able to leap over debris. Another that Hitachi is reportedly designing will resemble a snake so it can lower cameras through a grating in reactor No 1 to scope out and photograph melted down fuel there. That will be third Hitachi robot of that design.

Another robot designed by Toshiba, which was widely eulogized throughout the media, was designed to the anatomy of a scorpion. It died at the end of February just shy of a grating through which it might have got a peek of melted down fuel in reactor No 2.

Newer robot designs, according to a Tepco spokesman who talked with Bloomberg, are incorporating fewer wires and circuits and are built with harder parts than their earlier cousins.

But even the robots that peter out in the radiation are providing valuable clues: Toshiba’s scorpion robot sent the first grainy images from within reactor No 2 of a black residue that could actually be the spent fuel it was sent in to find.

Whether the fuel is in discrete piles or has melted to the walls of its containment vessels will present yet new challenges. Tepco and other scientists expect it’s a bit of both. Fuel that oozed and then re-melted inside the core or adhered to other reactor structures will have to be cut out, shoveled up and placed in shielded containers before it can be removed. This will be the robots’ job.

Earning the trust of a suspicious public

Six years of work is doing little to dent public suspicion of nuclear power in a country that previously relied on its 54 reactors to supply 30 percent of its power.

Tepco – which last year was shown to have delayed reporting the initial meltdowns after the catastrophe by 88 days, thus jeopardizing tens of thousands of lives – has a long way to got before it regains trust. Numerous other independent scientists are said by Japanese activists to be massaging data to make the situation look better than it is.

The mistrust is visible both in how slowly Japan is allowing its nuclear reactors go back online, and by the trickle of people who are willing to return to homes in the Fukushima Prefecture from which they were evacuated.

Japan’s reactors, all of which were shut down in the wake of the disaster, must pass the world’s most stringent stress tests before utilities can consider switching them back on. But even after they’re cleared technically, the people living near the plants have to want them back – and not many do.

As of this year, only three nuclear reactors have been switched on since 2011. Two others at the Genkai nuclear power plant on Japan’s Kyushu Island, were green lighted by a local mayor, but now must be approved by seven other surrounding municipalities.

In the most recently available national polls, taken last year on the fifth anniversary of the disaster, 70 percent of the population opposes the reactor restarts.

Among the more than 160,000 people reckoning with the dilemma of moving back to areas affected by radiation, 60 percent report feeling physical, psychological, financial and emotional stress as a result of the disaster, Japan’s NHK television reported. Up to 72,500 of these people still live in government supplied temporary housing.

In Naime, only 4 kilometers northwest of the plant, more than half of the resident have elected not to return, according to government surveys. Levels there recently hover around 0.07 microsieverts per hour, but down the road in Tomioka, they spike to 1.48 microsieverts an hour, more than 30 times levels in downtown Tokyo, showing there are still lingering radiation hotspots.

One group that is not afraid of populating the ghost-towns surrounding the plant are, according to reports, wild boar. The animals, which have grown up without humans around have reportedly grown fearless.

Tamotsu Baba, the mayor of Naime who is pushing for resettlement by the end of the month, told Reuters the boars pose make the town even less hospitable than the threat of radiation.

http://bellona.org/news/nuclear-issues/2017-03-six-years-on-fukushima-rests-its-hopes-on-fearless-robots

March 10, 2017 Posted by | Fukushima 2017 | , , , , | Leave a comment

Dying robots and failing hope: Fukushima clean-up falters six years after tsunami

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Exploration work inside the nuclear plant’s failed reactors has barely begun, with the scale of the task described as ‘almost beyond comprehension’

Barely a fifth of the way into their mission, the engineers monitoring the Scorpion’s progress conceded defeat. With a remote-controlled snip of its cable, the latest robot sent into the bowels of one of Fukushima Daiichi’s damaged reactors was cut loose, its progress stalled by lumps of fuel that overheated when the nuclear plant suffered a triple meltdown six years ago this week.

As the 60cm-long Toshiba robot, equipped with a pair of cameras and sensors to gauge radiation levels was left to its fate last month, the plant’s operator, Tokyo Electric Power (Tepco), attempted to play down the failure of yet another reconnaissance mission to determine the exact location and condition of the melted fuel.

Even though its mission had been aborted, the utility said, “valuable information was obtained which will help us determine the methods to eventually remove fuel debris”.

The Scorpion mishap, two hours into an exploration that was supposed to last 10 hours, underlined the scale and difficulty of decommissioning Fukushima Daiichi – an unprecedented undertaking one expert has described as “almost beyond comprehension”.

Cleaning up the plant, scene of the world’s worst nuclear disaster since Chernobyl after it was struck by a magnitude-9 earthquake and tsunami on the afternoon of 11 March 2011, is expected to take 30 to 40 years, at a cost Japan’s trade and industry ministry recently estimated at 21.5tr yen ($189bn).

The figure, which includes compensating tens of thousands of evacuees, is nearly double an estimate released three years ago.

The tsunami killed almost 19,000 people, most of them in areas north of Fukushima, and forced 160,000 people living near the plant to flee their homes. Six years on, only a small number have returned to areas deemed safe by the authorities.

Developing robots capable of penetrating the most dangerous parts of Fukushima Daiichi’s reactors – and spending enough time there to obtain crucial data – is proving a near-impossible challenge for Tepco. The Scorpion – so called because of its camera-mounted folding tail – “died” after stalling along a rail beneath the reactor pressure vessel, its path blocked by lumps of fuel and other debris.

The device, along with other robots, may also have been damaged by an unseen enemy: radiation. Before it was abandoned, its dosimeter indicated that radiation levels inside the No 2 containment vessel were at 250 sieverts an hour. In an earlier probe using a remote-controlled camera, radiation at about the same spot was as high as 650 sieverts an hour – enough to kill a human within a minute.

Shunji Uchida, the Fukushima Daiichi plant manager, concedes that Tepco acquired “limited” knowledge about the state of the melted fuel. “So far we’ve only managed to take a peek, as the last experiment with the robot didn’t go well,” he tells the Guardian and other media on a recent visit to the plant. “But we’re not thinking of another approach at this moment.”

Robotic mishaps aside, exploration work in the two other reactors, where radiation levels are even higher than in reactor No 2, has barely begun. There are plans to send a tiny waterproof robot into reactor No 1 in the next few weeks, but no date has been set for the more seriously damaged reactor No 3.

Naohiro Masuda, the president of Fukushima Daiichi’s decommissioning arm, says he wants another probe sent in before deciding on how to remove the melted fuel.

Despite the setbacks, Tepco insists it will begin extracting the melted fuel in 2021 – a decade after the disaster – after consulting government officials this summer.

But Shaun Burnie, a senior nuclear specialist at Greenpeace Germany who is based in Japan, describes the challenge confronting the utility as “unprecedented and almost beyond comprehension”, adding that the decommissioning schedule was “never realistic or credible”.

The latest aborted exploration of reactor No 2 “only reinforces that reality”, Burnie says. “Without a technical solution for dealing with unit one or three, unit two was seen as less challenging. So much of what is communicated to the public and media is speculation and wishful thinking on the part of industry and government.

The current schedule for the removal of hundreds of tons of molten nuclear fuel, the location and condition of which they still have no real understanding, was based on the timetable of prime minister [Shinzo] Abe in Tokyo and the nuclear industry – not the reality on the ground and based on sound engineering and science.”

Even Shunichi Tanaka, the chairman of Japan’s nuclear regulation authority, does not appear to share Tepco’s optimism that it will stick to its decommissioning roadmap. “It is still early to talk in such an optimistic way,” he says. “At the moment, we are still feeling around in the dark.”

The situation is not under control’

On the surface, much has changed since the Guardian’s first visit to Fukushima Daiichi five years ago.

Then, the site was still strewn with tsunami wreckage. Hoses, pipes and building materials covered the ground, as thousands of workers braved high radiation levels to bring a semblance of order to the scene of a nuclear disaster.

Six years later, damaged reactor buildings have been reinforced, and more than 1,300 spent fuel assemblies have been safely removed from a storage pool in reactor No 4. The ground has been covered with a special coating to prevent rainwater from adding to Tepco’s water-management woes.

Workers who once had to change into protective gear before they approached Fukushima Daiichi now wear light clothing and simple surgical masks in most areas of the plant. The 6,000 workers, including thousands of contract staff, can now eat hot meals and take breaks at a “rest house” that opened in 2015.

But further up the hill from the coastline, row upon row of steel tanks are a reminder of the decommissioning effort’s other great nemesis: contaminated water. The tanks now hold about 900,000 tons of water, with the quantity soon expected to reach 1m tons.

Tepco’s once-vaunted underground ice wall, built at a cost of 24.5bn yen, has so far failed to completely prevent groundwater from leaking into the reactor basements and mixing with radioactive coolant water.

The structure, which freezes the soil to a depth of 30 metres, is still allowing 150 tonnes of groundwater to seep into the reactor basements every day, said Yuichi Okamura, a Tepco spokesman. Five sections have been kept open deliberately to prevent water inside the reactor basements from rising and flowing out more rapidly. “We have to close the wall gradually,” Okamura said. “By April we want to keep the influx of groundwater to about 100 tonnes a day, and to eliminate all contaminated water on the site by 2020.”

Critics of the clean-up note that 2020 is the year Tokyo is due to host the Olympics, having been awarded the Games after Abe assured the International Olympic Committee that Fukushima was “under control”.

Mitsuhiko Tanaka, a former Babcock-Hitachi nuclear engineer, accuses Abe and other government officials of playing down the severity of the decommissioning challenge in an attempt to win public support for the restart of nuclear reactors across the country.

Abe said Fukushima was under control when he went overseas to promote the Tokyo Olympics, but he never said anything like that in Japan,” says Tanaka. “Anyone here could see that the situation was not under control.

If people of Abe’s stature repeat something often enough, it becomes accepted as the truth.”

https://www.theguardian.com/world/2017/mar/09/fukushima-nuclear-cleanup-falters-six-years-after-tsunami

March 10, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment

Tepco’s biggest hurdle: How to remove melted fuel from crippled Fukushima reactors

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Tepco’s scorpion-shaped robot. | IRID

Six years after the triple meltdown at the Fukushima No. 1 nuclear power plant, recent investigations underneath the damaged reactor 2 using cameras and robots came close to identifying melted fuel rods for the first time.

Experts say getting a peek inside the containment vessel of reactor 2 was an accomplishment. But it also highlighted how tough it will be to further pinpoint the exact location of the melted fuel, let alone remove it some time in the future.

The biggest hurdle is the extremely lethal levels of radiation inside the containment vessel that not only prevent humans from getting near but have also crippled robots and other mechanical devices.

Safely removing the melted fuel would be a best-case scenario but the risks and costs should be weighed against the option of leaving the melted fuel in the crippled reactors, some experts said.

The work to probe inside the containment vessels and remove the fuel debris will be extremely tough because of the high radiation levels,” said Hiroshi Miyano, who heads a panel of the Atomic Energy Society of Japan, which is discussing ways to decommission the Fukushima plant and making recommendations to the government.

The government and Tokyo Electric Power Company Holdings Inc. are trying to find a way to remedy the situation but existing methods and technologies may not be sufficient, Miyano said.

In search of melted fuel

The world’s attention turned to the melted fuel rods in late January when Tepco inserted a 10-meter-plus tube equipped with a camera into the containment vessel of reactor 2 to capture images under the pressure vessel that housed the fuel rods.

The images showed black lumps scattered beneath the pressure vessel.

When the March 11, 2011, Great East Japan Earthquake and monstrous tsunami hit, the plant suffered a blackout and lost its key cooling system, triggering meltdowns in reactors 1, 2 and 3. The melted nuclear fuel rods penetrated the pressure vessels and fell into the containment vessels.

Tepco had put cameras inside the containment vessels several times in the past six years but January’s probe was the first to apparently find melted fuel debris.

We understand that this is a big milestone. We could finally get to see what it was like underneath the pressure vessel,” said Yuichi Okamura, general manager of Tepco’s nuclear power and plant siting division.

This is critical information in order to remove the fuel debris.”

Radiation barrier

But Tepco hasn’t confirmed that the black lumps are melted fuel, saying they could be paint or cable wrappings, and further investigation is needed.

Capturing the images may be progress but the robot and camera forays have not provided enough information about how to deal with the melted fuel.

Last month, Tepco sent a remote-controlled, scorpion-shaped robot in to further probe inside the reactor 2 containment vessel. But the robot failed before it reached under the pressure vessel after a tire became stuck.

The robot’s dosimeter measured radiation levels of 210 sieverts per hour — enough to kill humans instantly.

While 210 sieverts per hour indicate the melted fuel was nearby, the radiation crippled the robot’s electronics, including its semiconductors and cameras, indicating that the further use of robots to pinpoint the melted fuel will be difficult, robotics experts said.

There are computer chips “designed to withstand a certain level of radiation, but the level inside the containment vessel is totally different,” said Satoshi Tadokoro, a professor at Tohoku University who is an expert on disasters and rescue robots.

The radiation can damage a robot’s chips that serve as their brains, causing the devices to lose control, said Tadokoro, whose robots have also been used at the Fukushima plant.

On top of the high level of radiation, the entrance (to the containment vessel) for the robot is very small,” restricting what types of robots can be used to hunt for the melted fuel, he said.

Tepco said the opening it created on the side of the reactor 2 containment vessel is about 11 cm in diameter.

Fuel removal strategy

Tepco is set to conduct internal probes of the reactor 1 containment vessel this month and is preparing similar missions for reactor 3.

The government and utility then plan to adopt a basic fuel removal strategy this summer and fine-tune the plan next year, with the actual fuel removal taking place in or after 2021.

There are essentially three options for the strategy, according to the Tokyo-based International Research Institute for Nuclear Decommissioning (IRID), which is developing technologies for the Fukushima plant decommission.

One option is to flood the containment vessels with water and use a crane above the reactors to hoist up the melted fuel. The second option is to carry out the same process but without water. The third is to install removal equipment through the side of the containment vessel.

There are merits and drawbacks to each option, said Shoji Yamamoto, who heads the team developing technologies to create the fuel removal devices at IRID.

The flooding option can block radiation using water, but if the fuel melts into the water, it could pose a risk of recriticality. The debris may need to be cut into pieces for removal, but this process would enable water to get between multiple pieces, creating the condition for recriticality. For nuclear chain reactions to happen there needs to be a certain distance between nuclear fuel and water.

If there is no water, the recriticality risk is minimal but the massive radiation levels cannot be blocked, Yamamoto said.

Tepco’s Okamura said being able to block radiation with water is a huge plus, but noted the reactor 2 containment vessel had cracks and holes that could let injected coolant water escape.

With the Three Mile Island nuclear accident in the U.S., the flooding option was used to retrieve the melted fuel in the 1980s. But the key difference was that all of the melted fuel stayed inside the pressure vessel, so it was easier to flood the reactor.

Because the melted fuel in reactors 1, 2 and 3 at the Fukushima plant all penetrated the pressure vessels and fell into the containment vessels, extracting it from the top or the side was a tough call, Yamamoto said, noting it was important to know the exact location of the melted fuel.

The distance between the top of the pressure vessel and the bottom of the containment vessel is about 45 meters and some parts inside the pressure vessels will need to be removed if Tepco tries to remove the debris inside the containment vessels from the top.

If we know that the melted fuel is concentrated in the containment vessels, it will be more efficient to remove it from the side” because the entry point is closer, Yamamoto said.

Whatever option is decided, Yamamoto stressed that maintaining the fuel removal device will be difficult because the radiation will probably cripple it.

The fuel removal device will be controlled remotely … it will be broken somewhere down the line and the parts will have to be replaced, considering its (ability to withstand) radiation,” he said.

Given that, maintenance will have to be done remotely, too, and that will be a big challenge.”

To remove or not

Another option altogether is for Tepco to leave the melted fuel where it is.

During a media tour of the Fukushima No. 1 plant last month, Okamura of Tepco said the utility intended to collect the melted fuel because leaving it was “not an appropriate way” to manage nuclear fuel.

Miyano of the Atomic Energy Society of Japan said the debris must be removed because radioactive materials, including nuclear fuel, must be strictly controlled under international rules requiring strict monitoring.

Domestic nuclear power plant operators have to report the amount of nuclear fuel they have to the Nuclear Regulation Authority, which then reports to the International Atomic Energy Agency.

There is the question of whether the government and Tepco decide not to remove the fuel debris. That would be an international issue,” said Miyano, adding that a consensus from the international community would be needed.

At the same time, Miyano said debate and analysis will be required to decide which choice would be best by looking at various factors, including how much it will cost to pick up all the melted fuel and where to store it.

http://www.japantimes.co.jp/news/2017/03/09/national/tepcos-biggest-hurdle-remove-melted-fuel-crippled-fukushima-reactors/#.WMFAFKKmnIV

March 10, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment

Melted Nuclear Fuel Search Proceeds One Dead Robot at a Time

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The latest robot seeking to find the 600 tons of nuclear fuel and debris that melted down six year ago in Japan’s wrecked Fukushima Dai-Ichi power plant met its end in less than a day.

The scorpion-shaped machine, built by Toshiba Corp., entered the No. 2 reactor core Thursday and stopped 3 meters (9.8 feet) short of a grate that would have provided a view of where fuel residue is suspected to have gathered. Two previous robots aborted similar missions after one got stuck in a gap and another was abandoned after finding no fuel in six days.

After spending most of the time since the 2011 disaster containing radiation and limiting ground water contamination, scientists still don’t have all the information they need for a cleanup that the Japanese government estimates will take four decades and cost 8 trillion yen ($70.6 billion). It’s not yet known if the fuel melted into or through the containment vessel’s concrete floor, and determining the fuel’s radioactivity and location is crucial to inventing the technology needed to remove it. 

The roadmap for removing the fuel is going to be long, 2020 and beyond,” Jacopo Buongiorno, a professor of nuclear science and engineering at the Massachusetts Institute of Technology, said in an e-mail. “The re-solidified fuel is likely stuck to the vessel wall and vessel internal structures. So the debris have to be cut, scooped, put into a sealed and shielded container and then extracted from the containment vessel. All done by robots.”

Read more: Robots are being utilized to clean up U.K.’s nuclear waste

To enter a primary containment vessel, which measures about 20 meters at its widest, more than 30 meters tall and is encased in meters of concrete, outside air pressure is increased to keep radiation from escaping and a sealed hole is opened that the robot passes through. Three reactors at the plant suffered meltdowns, and each poses different challenges and requires a custom approach for locating and removing the fuel, said Tatsuhiro Yamagishi, Tokyo Electric Power Co. Holdings Inc. spokesman.

The machines are built with specially hardened parts and minimal electronic circuitry so that they can withstand radiation, if only for a few hours at a time. Thursday’s mission ended after the robot’s left roller-belt failed, according to Tokyo Electric, better known as Tepco. Even if it had returned, this robot, like all others so far designed to aid the search for the lost fuel, was expected to find its final resting place inside a reactor.

No. 1 Unit

Hitachi Corp. in the next two months plans to send a machine into the No. 1 reactor core that scientists hope can transmit photos of the fuel and measure radiation levels.

The snake-like robot will lower a camera on a wire from a grate platform in the reactor to take photos and generate 3-D models of the bottom of the containment vessel. This will be the third time Hitachi sends in this robot design.

While the company is hopeful this robot will find some of the fuel, it will likely be unable to find all of it, according to Satoshi Okada, a Hitachi engineer working on the project. The company is already planning the next robot voyage for after April.

We are gathering information so that we can decide on a way to remove the fuel,” said Okada. “Once we understand the situation inside, we will be able to see the way to remove the fuel.”

No. 2 Unit

On Thursday, Toshiba’s scorpion-like robot entered the reactor and stopped short of making it onto the containment vessel’s grate. While Tepco decided not to retrieve it, the company views the attempt as progress.

We got a very good hint as to where the fuel could be from this entire expedition” Tepco official Yuichi Okamura said Thursday at a briefing in Tokyo. “I consider this a success, a big success.”

Tepco released images last month of a grate under the No. 2 reactor covered in black residue that may be the melted fuel — one of the strongest clues yet to its location. The company measured radiation levels of around 650 sieverts per hour through the sound-noise in the video, the highest so far recorded in the Fukushima complex.

A short-term, whole-body dose of over 10 sieverts would cause immediate illness and subsequent death within a few weeks, according to the World Nuclear Association.

The Hitachi and Toshiba robots are designed to handle 1,000 sieverts and no robot has yet been disabled due to radiation.

Radiation levels near the fuel are lethal,” said MIT’s Buongiorno, who holds the university’s Tepco chair, a professorship based on an initial donation by the company 10 years ago. There are no formal affiliations or obligations for the faculty who receive the chair, he said.

Because the No. 2 unit is the only one of the three reactors that didn’t experience a hydrogen explosion, there was no release into the atmosphere and radiation levels inside the core are higher compared to the other two units, according to the utility.

No. 3 Unit

Tepco’s balance sheet has been strapped by ballooning Fukushima cleanup costs and slumping national power demand. All of the company’s nuclear power plants remain shut since it halted the No. 6 reactor at its Kashiwazaki Kariwa station in March 2012. The company is seeking drastic changes in top management in consultation with the Japanese government, TV Asahi reported Friday, without attribution.

The utility has focused on removing spent fuel in the upper part of the reactor building, which Toshiba aims to extract with a claw-like system. This fuel didn’t melt and is still in a pool that controls its temperature.

The used-fuel in No. 3 is scheduled to begin removal before the end of the decade, the first among the three reactors that melted down. Toshiba is developing another robot to search for melted fuel, planned to enter sometime in the year ending March 2018. The company hasn’t announced yet the design or strategy.

https://about.bnef.com/blog/race-for-japans-melted-nuclear-fuel-leaves-trail-of-dead-robots/

February 21, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment

In Fukushima, even robots can’t survive nuclear mayhem

The company that runs the Fukushima plant sent 5 robots to ground zero and not a single one survived. Incredibly high radiations in the block causes heat levels to rise and this melts the robots’ wiring.

A tsunami, triggered by an earthquake on March 11, 2011, initiated the Fukushima Daaiichi nuclear disaster in Japan which led to the evacuation of over 200,000 people.

Even after 5 years, there is still a tremendous amount of cleanup work left at ground zero. The Tokyo Electric Power Co. (TEPCO) which runs the plant has managed to clean up one building but is still struggling to do the same with other buildings which has burnt fuel rods. These fuel rods are nothing but chunks of radioactive waste weighing hundreds of metric tonnes.

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It took 2 years for TEPCO to design the robots for the job of extracting melted fuel rods and according to TEPCO’s head of decommissioning, Naohiro Masuda, the heat levels due to radiation are so extreme that it simply melts the robot’s wiring.

Japan had been trying out various methods to stop the radiations from damaging the area further. One such method was building “ice walls” to keep groundwater from reaching the reactors. A refrigerant chemical that forms an ice wall to block Fukushima’s fallout water and stop the ground water intrusion into the plant.

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A million metric tonnes of irradiated water is being stored on the site and is pumped in to cool down the reactors. Disposing the radioactive water is still a challenge for TEPCO as storage tanks have already leaked some of the material into the ocean.

After TEPCO’s robots not surviving the heat levels of the radiations, it’s a place for no man or machine. Toshiba has developed new robots for picking up the fuel rods and to clean up the scene which previous robots failed to.

The entire cleanup process is expected to take around 30 to 40 years, but TEPCO is being blamed for its lukewarm response to the incident and is facing flak from the Japanese government and the people alike.

http://indiatoday.intoday.in/story/in-fukushima-even-robots-cant-survive-nuclear-mayhem/1/678028.html

May 27, 2016 Posted by | Fukushima 2016 | , , , , , | Leave a comment