The call might have been made to decommission five over-the-hill nuclear reactors, but the problem remains of where to dispose of their total 26,820 tons of radioactive waste.
The plant operators have yet to find disposal sites, and few local governments are expected to volunteer to store the waste on their properties.
The decommissioning plans for the five reactors that first went into service more than 40 years ago was green-lighted by the Nuclear Regulation Authority on April 19.
It is the first NRA approval for decommissioning since the 2011 Fukushima nuclear disaster triggered by the Great East Japan earthquake and tsunami.
That disaster led to a new regulation putting a 40-year cap, in principle, on the operating life span of reactors.
The reactors to be decommissioned are the No. 1 reactor at Japan Atomic Power Co.’s Tsuruga plant in Fukui Prefecture; the No. 1 reactor at Kyushu Electric Power Co.’s Genkai plant in Saga Prefecture; the No. 1 and No. 2 reactors at Kansai Electric Power Co.’s Mihama plant in Fukui Prefecture; and the No. 1 reactor at Chugoku Electric Power Co.’s Shimane plant in Shimane Prefecture.
The decommissioning will be completed between fiscal 2039 and fiscal 2045 at a total cost of 178.9 billion yen ($1.64 billion), according to the utilities.
In the process, the projects are expected to produce 26,820 tons of radioactive waste–reactors and pipes included.
An additional 40,300 tons of waste, such as scrap construction material, will be handled as nonradioactive waste due to radiation doses deemed lower than the government safety limit.
Securing disposal sites for radioactive waste has proved a big headache for utilities.
About 110 tons of relatively high-level in potency radioactive waste, including control rods, are projected to pile up from the decommissioning of the No. 1 reactor at the Mihama plant.
Such waste needs to be buried underground deeper than 70 meters from the surface and managed for 100,000 years, according to the NRA’s guidelines.
In addition, the decommissioning of the same reactor will generate 2,230 tons of less toxic waste as well, including pipes and steam generators.
Under the current setup, utilities must secure disposal sites on their own.
Kansai Electric, the operator of the Mihama plant, has pledged to find a disposal site “by the time the decommissioning is completed.”
But Fukui Prefecture, which hosts that plant and others, is demanding the waste from the Mihama facility be disposed of outside its borders.
The project to dismantle the reactor and other facilities has been postponed at Japan Atomic Power’s Tokai plant in Ibaraki Prefecture because the company could not find a disposal site for the relatively high-level waste.
The decommissioning of the reactor had been under way there since before the Fukushima disaster.
The expected difficulty of securing disposal sites could jeopardize the decommissioning timetable, experts say.
Even finding a disposal site for waste that will be handled as nonradioactive has made little headway.
What is more daunting is the hunt for a place to store high-level radioactive waste that will be generated during the reprocessing of spent fuel, they said.
String of facilities approaching maximum life span
Workers take apart a pump at Chubu Electric Power’s Hamaoka nuclear plant.
TOKYO — Five nuclear reactors in Japan were approved for decommissioning on Wednesday, pushing utilities and other companies to join hands to tackle both the great business opportunities and daunting technical problems involved with the process.
Two reactors at Kansai Electric Power‘s Mihama plant, as well as one each at Japan Atomic Power’s Tsuruga plant, Chugoku Electric Power‘s Shimane plant and Kyushu Electric Power‘s Genkai facility received the green light from Japan’s Nuclear Regulation Authority. The safety updates needed to keep them running beyond their mandated 40-year life span were deemed too costly.
Japan had 54 nuclear reactors before the 2011 meltdown at the Fukushima Daiichi nuclear plant. A total of 15, including the six at Fukushima Daiichi, are now set to be taken out of service. Another one or two will be brushing up against the 40-year limit every year, unless one-time, 20-year extensions are sought and granted.
Companies now face a pressing need to acquire expertise on dismantling reactors and disposing of radioactive materials. No commercial nuclear reactor has ever been decommissioned in Japan before, and utilities are looking for partners with the necessary capabilities.
Kansai Electric is seeking help from France’s Areva and Japan’s Mitsubishi Heavy Industries in decommissioning the Nos. 1 and 2 reactors at Mihama, particularly in decontaminating pipes and equipment. Japan Atomic Power and U.S.-based EnergySolutions signed an agreement last spring to cooperate on the former’s Tsuruga plant.
Japanese utilities are also beginning to work with each other. Kansai Electric entered a partnership last year with Kyushu Electric, Chugoku Electric and Shikoku Electric Power. The four plan to cut decommissioning costs by jointly procuring materials and sharing technology and staffers.
Other players are also angling for a piece of the pie. Two years ago, Mitsubishi Heavy set up a department specializing in dismantling nuclear reactors. The company was a key player in building the Mihama and Genkai reactors, and wants a lead role in taking them apart. Japanese general contractor Shimizu also signed a technical cooperation agreement with U.K.-based Cavendish Nuclear.
Utilities have increased their rates in order to raise the necessary funds to decommission the five newly approved reactors. They have already come up with about 160 billion yen ($1.47 billion) of the estimated 180 billion yen total. But the process will likely take two or three decades, and costs could easily grow.
The utilities may also face significant challenges to disposing of the roughly 27,000 tons of contaminated waste the five reactors are expected to generate. For example, Japan Atomic Power wants to bury less radioactive materials at the site of the Tokai nuclear plant, one of the earlier plants approved for decommissioning, but faces strong local opposition.
Relevant legislation has not been finalized either. Highly contaminated materials are supposed to be buried more than 70 meters below ground. But the Nuclear Regulation Authority has only just begun debating exactly how they should be buried.
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.”
Tokyo Electric Power Company Holdings Inc. (TEPCO) has informally decided to decommission the No. 1 reactor at its Fukushima No. 2 Nuclear Power Plant, it has been learned.
In the wake of the March 2011 Great East Japan Earthquake and tsunami and ensuing meltdowns at the Fukushima No. 1 plant in Fukushima Prefecture, local bodies and residents of the area who suffered extensive damage requested that all four reactors at the No. 2 plant also be decommissioned.
TEPCO had avoided stating a clear position on the No. 2 plant’s reactors, but there had been pressure from the government and ruling coalition for it to make a decision. The company accordingly decided to decommission the plant’s No. 1 reactor, which suffered the most damage, and will consider what to do with the other three reactors in the future.
The No. 1 reactor of the Fukushima No. 2 plant began operating in 1982. It was flooded by tsunami on March 11, 2011, and all four reactors at the plant remain idled. The No. 2 plant suffered less damage than the No. 1 plant, and if it passed screening by the Nuclear Regulation Authority, its reactors could be restarted. But the Fukushima Prefectural Government and all 59 local assemblies have asked TEPCO and the government to decommission all reactors in the prefecture.
TEPCO has remained busy handling compensation claims relating to the Fukushima nuclear disaster and the disaster cleanup. If it were to decommission all of the No. 2 plant’s reactors, they would lose value and it would have to write down huge losses. Company president Naomi Hirose has therefore avoided taking a clear position on the issue, saying, “I would like to consider it and make a decision as a business operator.”
Last year, however, officials decided to create a fund to cover the huge cost of handling the nuclear disaster, which is expected to reach 21.5 trillion yen, nearly double the original prediction. There was accordingly pressure from the government for TEPCO to reach an early decision on the fate of the No. 2 plant’s reactors.
The No. 1 reactor at the No. 2 plant is the oldest of the plant’s four reactors. It temporarily lost its cooling functions in the March 2011 disaster, and suffered the most damage among the four reactors. TEPCO believes that by limiting decommissioning to one reactor for the time being, it will be able to hold the decommissioning cost below 100 billion yen, minimizing the impact on company finances and on decommissioning work at the Fukushima No. 1 plant. However, a decision to decommission only one reactor at the No. 2 plant is unlikely to win public approval.
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.
Arjun Makhijani is the President of the Institute for Energy and Environmental Research.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.”
Naohiro Masuda, head of decommissioning the damaged Fukushima nuclear plant, speaks at a news conference in Tokyo on March 2, 2017.
TOKYO (AP) — The head of decommissioning for the damaged Fukushima nuclear plant said Thursday that more creativity is needed in developing robots to locate and assess the condition of melted fuel rods.
Naohiro Masuda, president of Fukushima Dai-ichi decommissioning, said Thursday that more data is needed so they can develop a better strategy for removing debris. The plant’s operator, Tokyo Electric Power Co., and the government will decide on a method this summer.
Masuda said that a robot sent inside the Unit 2 containment vessel last month could not reach as close to the core area as hoped, because it was blocked on its planned route by deposits, believed to be mixture of melted fuel and broken pieces of equipment.
Masuda said he wants another probe sent in before deciding on methods to remove the reactor’s debris.
TEPCO needs to know the melted fuel’s exact location as well as structural damage in each of the three wrecked reactors to figure out the best and safest ways to remove the fuel.
Despite the incomplete probe missions, officials have said they want to stick to their schedule to determine the removal methods this summer and start work in 2021.
Unit 2 is one of the Fukushima reactors that melted down following the 2011 earthquake and tsunami. The unit had less damage to its containment vessel, so internal probes there are ahead of the other two reactors.
Still, the earlier probes have suggested worse-than-anticipated challenges for the plant’s cleanup, which is expected to take decades.
Similar probes are being planned for the other two reactors. A tiny waterproof robot will be sent into Unit 1 in coming weeks, while experts are still trying to figure out a way to access the badly damaged Unit 3.
TEPCO is struggling with the plant’s decommissioning. The 2011 meltdown forced tens of thousands of nearby residents to evacuate their homes, and many have still not been able to return home due to high radiation levels.
Images captured from inside the chamber show damage, and structures coated with molten material, possibly mixed with melted nuclear fuel.
The Japanese government has decided to maintain control over the operator of the damaged Fukushima Daiichi nuclear power plant for an extended period.
Officials made the decision due to rising costs from the recovery of the 2011 nuclear accident.
The government acquired a 50.1 percent stake in Tokyo Electric Power Company through a state-backed bailout fund after the accident. This put the utility under effective state control.
Under the current plan, the government was to gradually reduce its control after April by selling TEPCO stocks in phases, while monitoring the company’s management.
But the government estimates that it will cost a total of about 188 billion dollars to clean up the soil, pay compensation, and decommission reactors. That’s about twice as much as an earlier estimate.
The extension of state control over TEPCO means that the government has to give up the current plan to cover the clean-up cost of about 35 billion dollars by selling the utility’s shares.
The government is now considering listing a joint venture set up by TEPCO, and Chubu Electric Power Company, and selling its stocks. It is also looking into selling some shares of a TEPCO group company that operates a power transmission business.
The government intends to include these financial alternatives in the utility’s business plan which will be renewed for the first time in 3 years in spring.
This Week’s Featured Interview:
- Dr. Helen Caldicott on why Fukushima will never be able to be cleaned up; the devastating health impacts of radiation; and why the 2020 Tokyo Olympics are a really really bad idea.
- Dr. Caldicott Links:
KGO Radio: Host Pat Thurston recently interviewed Arnie Gundersen, chief engineer for Fairewinds Energy Education on KGO radio to discuss the latest challenging news from Japan about the Fukushima Daiichi atomic power reactor including the high levels of radiation emanating from the reactors, all the failed robotic expeditions, where we should go from here, as well as how ongoing radioactive releases from the Fukushima Daiichi site may be impacting the west coast of the United States.
BBC Newsday: BBC Radio interviewed nuclear engineer Arnie Gundersen to discuss TEPCO’s attempts to send a special robot into Fukushima Daiichi Reactor #2 in Japan to investigate the obstacles in the way of TEPCO’s progress determining the location and condition of the atomic fuel. Unfortunately even this specially designed robot failed in its attempt to clear the path for additional investigations as the nuclear radioactivity was so high, it shut down the robots before they could complete their mission.
Enviro News: The astronomical radiation readings at Fukushima Daiichi Reactor #2 of 530 Sv/hr complicate the already complex task of decommissioning the plant. These levels are so radioactive that a human would be dead within a minute of exposure and specially designed robots can only survive for about 2 hours. Fairewinds chief engineer Arnie Gundersen says that the best solution would be to entomb the reactors, similar to the sarcophagus entombing Chernobyl, for at least 100-years, otherwise the radiation level that workers would be exposed to is simply too dangerous.
Read the whole article here
Are the meltdowns at Fukushima Daiichi over? The answer is no. Made all the more prevalent a year out from it’s initial release by the recent robotic expeditions into Reactor #2 which gave us a clearer picture on just how deadly the radiation levels are, watch Chief Engineer and nuclear expert Arnie Gundersen inform viewers on what’s going on at the Japanese nuclear meltdown site, Fukushima Daiichi. As the Japanese government and utility owner Tokyo Electric Power Company push for the quick decommissioning and dismantling of this man-made disaster, the press and scientists need to ask, “Why is the Ukrainian government waiting at least 100 years to attempt to decommission Chernobyl, while the Japanese Government and TEPCO claim that Fukushima Daiichi will be decommissioned and dismantled during the next 30 years?”
Like so many big government + big business controversies, the answer has nothing to do with science, and everything to do with politics and money. To understand Fukushima Daiichi, you need to follow the money.
There are many shoes still to drop at Fukushima Daiichi, said Kevin Kamps, radioactive waste monitor at Beyond Nuclear. If something goes wrong with the radioactive waste storage pools, there could be a release of high-level radioactivity into the air, he added.
Radiation at Fukushima’s nuclear power plant is at its highest level since the tsunami-triggered meltdown nearly six years ago. Tokyo Electric Power Company (TEPCO) is reporting atmospheric readings inside Daiichi’s reactor No.2 are as high as 530 sieverts an hour, while a human exposed to a single dose of 10 sieverts would die in a couple of weeks.
RT: Can you explain what is likely going on here?
Kevin Kamps: This catastrophe that is ongoing is nearly six years old at this point. The fuel, the melted cores have been missing an action. TEPCO doesn’t know where they are; the Japanese government doesn’t know where they are; nobody knows where they are. What could have happened is these probes, these cameras, these robots, these radiation monitors that are being sent in by TEPCO to try to figure out what is going on, may have encountered the closest they have come yet to these melted cores. They may even have come upon melted fuel that is not under water, and water serves as a radiation shielding. So if this is an open area and there is no water – that could explain.
But what you’ve got are melted reactor cores. Of course, human beings can’t be in operating atomic reactors. They also can’t be in this area where there is a meltdown. There is also imagery – it looks like a melt through of a metal grade. It all stands to reason that the cores melted through the reactor pressure vessels and down into the containment structures right through that metal grating.
It is not unexpected, but we still don’t know where the cores are. There are claims that “it’s all contained, don’t worry about it.” It is indisputable that there is a daily flow of radioactively contaminated groundwater into the ocean. The figures something like 80,000 gallons per day of relatively low-level radioactive waste water. Then you’ve got those storage tanks – we’re talking 800,000 tons of highly radioactive water stored in tanks. Every day they pour a hundred tons of water on each of these three melted down cores. Sometimes they lose those tanks. They leak, they overflow – it is an ongoing catastrophe.
RT: So the contamination, in this case, could leak out, couldn’t it?
KK: There is some leakage on a daily basis. Then they try to capture as much as they can and contain it in the storage tanks, which they sometimes lose, whether during a typhoon or through human error – they have had overflows. So many shoes can still drop at Fukushima Daiichi. One of the ones is the high radioactive waste storage pools that aren’t even inside radiological containment. They don’t have all of that spent nuclear fuel transferred to a safer location in a couple of the units still. If something were to go wrong with that – those would be open air releases of very high-level radioactivity.
The prime minister at the time the catastrophe began, [Naoto] Kan, had a contingency plan to evacuate all of North-East Japan – up to 50 million people. It was predominantly because of those storage pools. We’re still in that predicament- if one of those pools were to go up in flames. As Tokyo plans to host the 2020 Olympics and bring in many millions of extra people into this already densely populated area -it is not a good idea.
RT: Going back to this specific leak: how does this complicate the cleanup efforts there? Is it possible even to get something in there right now to examine what is going on?
KK: State of the art robotic technology – Japan is a leader in robotics – can only last so long, because the electronics get fried by the gamma radiation, and probably neutron radiation that is in there. That is the situation deep in there. They are already saying it will take 40 years to so-called decommission this, but that may be optimistic.
RT: Also in December the government said it is going to take twice as much money – nearly twice as much as they originally thought – to decommission that. Does this make matters ever worse – this leak? Or is this just kind of the situation to expect at this point?
KK: It just shows how dire the situation is. The figures of $150 billion to decommission – I have seen figures from a think tank in Japan sided by Green Peace Japan up to $600 billion. If you do full cost accounting: where is this high-level radioactive waste going to go? It is going to need a deep geological depository. You have to build that and operate it. That costs a hundred billion or more. So when you do full cost accounting, this catastrophe could cost hundreds of billions of dollars to recover from. We’re just in the beginning.
Video footage of the inside of the No. 2 reactor at the Fukushima No. 1 Nuclear Power Plant has proved that it is more difficult than initially believed to decommission the tsunami-ravaged plant.
The camera that was inserted into an area below the reactor’s pressure vessel shows a deposited substance near a foothold in the area. The substance is highly likely to be melted nuclear fuel.
Nearly six years have passed since the March 2011 Great East Japan Earthquake and tsunami that triggered the nuclear crisis. The fact that the condition of the inside of the reactor has been confirmed represents a step forward. However, analysis conducted by Tokyo Electric Power Co. (TEPCO), the operator of the crippled power station, shows that the levels of radiation in the reactor building are so high that someone would die within less than a minute if they were exposed to radiation inside the facility. The footage shows that the deposited substances are scattered around in a wide area of the structure. TEPCO had planned to introduce a robot equipped with a camera into the reactor building possibly by the end of this month to fully probe the condition inside, but the footage has forced the utility to reconsider the plan.
If the situation is left as it is, the time required to decommission and dismantle the power station, which is believed to take 30 to 40 years, could be prolonged and the estimated costs of decommissioning the plant, which has already been revised upward from the initial 2 trillion yen to 8 trillion yen, could further rise. TEPCO is required to foot the costs of decommissioning the Fukushima plant, but the expenses will be passed on to consumers who pay electric power charges.
The government and TEPCO should fundamentally review their responses to the nuclear disaster, such as the development of technologies necessary to decommission the plant and ways to reduce decommissioning costs.
Meltdowns occurred in the cores of the No. 1 to 3 reactors at the Fukushima No. 1 Nuclear Power Plant in the accident. According to the road map toward decommissioning the plant, drawn up by the government and TEPCO, the utility is supposed to determine a method to remove melted fuel at one of the reactors by the end of fiscal 2018 and begin work within 2021.
To do so, it is necessary to ascertain where and how deposits of melted fuel are scattered, but this remains unclear.
TEPCO hit a snag at the beginning of the recent survey on the No. 2 reactor. Still, the condition of the reactor is far better than those of the No. 1 and 3 reactors — which were badly damaged in hydrogen explosions, obstructing surveys of their interiors.
Reactor core meltdowns occurred in an accident at a nuclear plant on Three Mile Island in the United States in 1979. Work to remove melted fuel commenced six years after the outbreak of the disaster and was completed 11 years after the accident. Workers remotely controlled a device to remove melted fuel from the pressure vessel while filling the vessel with water to block radiation.
Work at the Fukushima plant is far more difficult than at the Three Mile power station because nuclear fuel has melted and leaked out of the pressure vessels of the No. 1 to 3 reactors. How and where the melted fuel will be stored has not been decided yet. The government and TEPCO should obtain knowledge both from Japan and overseas to develop technologies to store melted fuel.
In considering the road map toward decommissioning the plant, it should be kept in mind that the degree of progress in the work will affect the restoration of areas hit by the nuclear disaster and the prospects for evacuated residents to return to their homes. However, if an unreasonably tight schedule is created, it could increase the risks of worker accidents and exposure to radiation.
Although it is a difficult task, the government and TEPCO are required to ensure transparency and steadily overcome obstacles to decommission the crippled power station.
The Tokai spent nuclear fuel reprocessing plant in Tokai, a village in Ibaraki Prefecture
TOKAI, Ibaraki Prefecture–Drums of nuclear waste are stacked in disarray within a storage pool containing unidentified floating objects. Wires in the pool are feared entangled, and containers are believed corroded, possibly leaking radioactive substances. And highly toxic liquid waste remains untreated in a potentially explosive state.
After years of apparent mismanagement, the Tokai spent nuclear fuel reprocessing plant is a jumbled mess, as the operator, Japan Atomic Energy Agency (JAEA), prepares for the Herculean task of shutting down the facility.
The circumstances at the plant in this village northeast of Tokyo has raised concerns about the JAEA’s ability to dismantle it.
“A situation far from appropriate has been allowed to continue at the plant,” said an official of the Nuclear Regulation Authority, the nation’s nuclear watchdog. “Not only the JAEA, but also the former Science and Technology Agency and the former Nuclear and Industrial Safety Agency, have all looked the other way despite their knowledge of the situation.”
According to a JAEA report submitted to the NRA on Nov. 30, it will take 70 years to complete the dismantling process, with costs estimated at 217 billion yen ($1.92 billion) for the first decade alone.
A recent visit to the plant by Asahi Shimbun reporters revealed drums containing radioactive waste stacked in a disorderly manner in a storage pool.
JAEA officials showed pictures of the pool and explained that it contains about 800 drums piled about 7 meters high. The drums hold demolished clads from spent nuclear fuel assemblies.
The officials said that when an underwater camera was placed near the drums, it stirred up brown objects.
“We have no idea if they are water scale or rust,” one of JAEA officials said.
Workers put the drums in the storage pool between 1977 and 1994 by hanging them with cables above the pool and then cutting the cables to allow them to drop in, according to the officials.
The officials said they believed the cables also fell into the pool and became entangled.
Some experts at the NRA suspect the drums are now corroded and leaking radioactive materials.
Radiation at the pool surface measured 3 millisieverts per hour, three times the safety limit for annual exposure for a person, apart from background radiation.
The pool is not equipped with purification units.
Furthermore, JAEA officials said they do not know what’s in other containers at the facility.
Workers will eventually sort them out by opening their lids, they added.
One of the most challenging tasks facing the JAEA in the dismantling work is dealing with the 400 cubic meters of high-level radioactive liquid waste at the plant.
The liquid waste, which was generated during reprocessing, emits radiation registering 1,500 sieverts per hour, which would kill a person exposed for 20 seconds.
Left intact, this waste could produce heat and hydrogen, possibly leading to hydrogen explosions.
The JAEA has put the liquid waste in six stainless tanks and kept them cool with water. A ventilation system has been used to prevent hydrogen from accumulating inside the storage facility and sparking an explosion.
Ibaraki Prefecture is located immediately south of Fukushima Prefecture.
The Great East Japan Earthquake and tsunami that struck northeastern Japan in 2011 severed all power sources to the Fukushima No. 1 nuclear power plant, leading to hydrogen explosions and the triple meltdown there.
The natural disaster also cut off electricity to the Tokai plant for more than 40 hours. But the plant rode out the contingency with emergency power generators.
The NRA is aware of risks involved in keeping the liquid waste in the current state at the Tokai plant.
In 2013, the NRA allowed the plant to resume operations to solidify the liquid waste with glass as a special case before the watchdog checked whether the plant met tougher nuclear safety regulations set after the Fukushima disaster.
Work on the solidification process resumed this year, but it has been suspended because of a series of glitches. Only one-fourth of the scheduled volume of the liquid waste has been solidified.
The reprocessing plant began full operations in 1981. It had reprocessed 1,140 tons of spent nuclear fuel before the decision was made in 2014 to close down the facility.
A test using a model of the No. 2 reactor’s suppression chamber and torus room at the Fukushima No. 1 plant is demonstrated for media in Naraha, Fukushima Prefecture, on Tuesday.
NARAHA, FUKUSHIMA PREF. – A research institute used a full-size mock-up of part of a nuclear reactor on Tuesday to conduct trial decommissioning experiments for use on the disaster-hit Fukushima No. 1 plant.
The International Research Institute for Nuclear Decommissioning (IRID) carried out the experiments using a 20-meter wide, 12-meter high model of the No. 2 reactor’s suppression chamber and torus room — areas located below the reactor’s containment vessel.
IRID was established in 2013 by nuclear plant makers, power firms and government organizations to develop technology needed for the decommissioning of the Fukushima plant, which was damaged by the March 3, 2011 earthquake and tsunami. After the disaster, three of the plant’s reactors suffered meltdowns in the world’s most severe nuclear crisis since the 1986 Chernobyl disaster.
The model is located at the Naraha Remote Technology Development Center, near the crippled Fukushima No. 1 plant.
“We would like to continue testing until next summer, approximately, and use (the outcomes) in deciding methods to retrieve fuel debris,” Atsufumi Yoshizawa, IRID executive director, said.
Removing nuclear fuel debris is perceived as one of the most difficult challenges in the decommissioning process.
With radiation emitting from the debris, a method is under consideration to fill containment vessels at the plant with water and remove debris from the top of the vessels, using the water to provide some protection from the harmful radiation.
Challenges in implementing this method include how to prevent contaminated water leaking from cracks in the vessels.
During Tuesday’s experiments, which were open to the media, workers wearing protective suits and masks attempted to insert a hose into the torus room mock-up while using remote cameras to observe their work.
A further experiment to stop water leaking from a suppression chamber is planned.
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