Japan pictures likely show melted Fukushima fuel for first time — Bloomberg

” New images show what is likely to be melted nuclear fuel hanging from inside one of Japan’s wrecked Fukushima reactors, a potential milestone in the cleanup of one of the worst atomic disasters in history.

Tokyo Electric Power Co. Holdings Inc., Japan’s biggest utility, released images on Friday showing a hardened black, grey and orange substance that dripped from the bottom of the No. 3 reactor pressure vessel at Fukushima, which is likely to contain melted fuel, according to Takahiro Kimoto, an official at the company. The company sent a Toshiba-designed robot, which can swim and resembles a submarine, to explore the inside of the reactor for the first time on July 19.

“Never before have we taken such clear pictures of what could be melted fuel,” Kimoto said at a press briefing that began at 9 p.m. Friday in Tokyo, noting that it would take time to analyze and confirm whether it is actually fuel. “We believe that the fuel melted and mixed with the metal directly underneath it. And it is highly likely that we have filmed that on Friday.”

If confirmed, the substance — which has the appearance of icicles — would be the first discovery of the fuel that melted during the triple reactor accident at Fukushima six years ago. For Tokyo Electric, which bears most of the clean-up costs, the discovery would help the utility design a way to remove the highly-radioactive material.

The robot, which is about 30 centimeters (12 inches) long, will search for melted fuel at the bottom of the reactor on Saturday. It is possible that the company will take more pictures of what could be melted fuel spread across the floor and lower levels, according to Tokyo Electric’s Kimoto. Fuel from a nuclear meltdown is known as corium, which is a mixture of the atomic fuel rods and other structural materials.

Early Signs

“It is important to know the exact locations and the physical, chemical, radiological forms of the corium to develop the necessary engineering defueling plans for the safe removal of the radioactive materials,” said Lake Barrett, a former official at the U.S. Nuclear Regulatory Commission who was involved with the cleanup at the Three Mile Island nuclear power plant in the U.S. “The recent investigation results are significant early signs of progress on the long road ahead.”

Because of the high radioactivity levels inside the reactor, only specially designed robots can probe the unit. And the unprecedented nature of the Fukushima disaster means that Tepco, as the utility is known, is pinning its efforts on technology not yet invented to get the melted fuel out of the reactors.

Removal Plans

The company aims to decide on the procedure to remove the melted fuel from each unit as soon as this summer. And it will confirm the procedure for the first reactor during the fiscal year ending March 2019, with fuel removal slated to begin in 2021.

Decommissioning the reactors will cost 8 trillion yen ($72 billion), according to an estimate in December from the Ministry of Economy, Trade and Industry. Removing the fuel is one of the most important steps in a cleanup that may take as long as 40 years.

Similar to the latest findings on Friday, Tepco took photographs in January of what appeared to be black residue covering a grate under the Fukushima Dai-Ichi No. 2 reactor, which was speculated to have been melted fuel. However, a follow-up survey by another Toshiba-designed robot in February failed to confirm the location of any melted fuel in the reactor after it got stuck in debris.

A robot designed by Hitachi-GE Nuclear Energy Ltd. also failed to find any melted fuel during its probe of the No. 1 reactor in March.

The significance of Friday’s finding “might be evidence that the robots used by Tepco can now deal with the higher radiation levels, at least for periods of time that allow them to search parts of the reactor that are more likely to contain fuel debris,” M.V. Ramana, professor at the Liu Institute for Global Issues at the University of British Columbia, said by email.

“If some of these fragments can be brought out of the reactor and studied, it would allow nuclear engineers and scientists to better model what happened during the accident.” ”

by Stephen Stapczynski, Bloomberg

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Fukushima’s ¥8 trillion cleanup leaves foreign firms in the cold — The Japan Times

” Cleaning up the Fukushima nuclear plant — a task predicted to cost 86 times the amount earmarked for decommissioning Japan’s first commercial reactor — is the mother of all salvage jobs. Still, foreign firms with decades of experience are seeing little of the spoils.

Safely dismantling the Japanese power plant, wrecked by the 2011 earthquake and tsunami, will cost about ¥8 trillion ($70 billion), the Ministry of Economy, Trade and Industry said on Dec. 9, quadrupling the previous estimate. While a contract to help clean up the facility would be a windfall for any firm with specialized technology, the lion’s share of the work has gone to local companies that designed and built most of Japan’s atomic infrastructure.

The bidding process for Fukushima contracts should be more open to foreigners, as Japan has never finished decommissioning a commercial nuclear plant, let alone one that experienced a triple meltdown, according to Lake Barrett, an independent adviser at Japan’s International Research Institute for Nuclear Decommissioning. While the Fukushima cleanup is unlike any nuclear disaster in history, foreign firms that have experience decommissioning regular facilities could provide much-needed support, according to Barrett, and even the plant’s operator, Tokyo Electric Power Co. Holdings Inc.

‘Cultural Resistance’

“Internationally, there is a lot more decontamination and decommissioning knowledge than you have in Japan,” Barrett, a former official at the U.S. Nuclear Regulatory Commission, said in an interview in Tokyo. “I hope the Japanese contracting system improves to get this job done safely. There is this cultural resistance — it is almost like there is an isolated nuclear village still.”

An opaque bidding process plays to the heart of criticisms put forward by independent investigators, who said in a 2012 report that collusion between the government, regulators and the plant’s operator contributed to the scale of the disaster.

Of 44 subsidized projects publicly awarded by the trade and economy ministry since 2014, about 80 percent went to the International Research Institute for Nuclear Decommissioning. The group, known as IRID, was established in the wake of the Fukushima disaster and is comprised entirely of Japanese corporations, according to the ministry’s website.

Japan’s trade and industry ministry awarded funds directly to only two foreign firms during the same period. Many of the contracts had only one or two bidders.

Of about 70 contracts awarded since the March 2011 disaster, nine have gone to foreign companies, according to an official in the ministry’s Agency of Natural Resources and Energy who asked not be named, citing internal policy.

To provide opportunities for foreign companies, the ministry has created an English website for bids and also provides English information sessions to explain the contracts, the official said.

Toshiba, Hitachi

IRID’s contracts are given to its members, including Toshiba Corp., Hitachi Ltd. and Mitsubishi Heavy Industries Ltd., which have partnerships and joint ventures with foreign firms, spokesman Yoshio Haruyama said by phone. While it doesn’t directly contract work to companies overseas, IRID taps foreign experts as advisers and participates in international collaborative projects, he said.

Mitsubishi Heavy has about five or six contracts through IRID, but can’t share how many partnerships it has with foreign firms, spokesman Shimon Ikeya said by phone. Hitachi has sub-contracts with foreign suppliers related to the Fukushima cleanup, but can’t provide details about these agreements because they aren’t public, a spokesperson said by email.

As of March, IRID had about ¥30 billion worth of ongoing contracts primarily related to research and development of fuel removal and waste treatment. IRID, which aims to “gather knowledge and ideas from around the world” for the purpose of nuclear decommissioning, doesn’t disclose how much of their money ultimately goes to foreign businesses, according to its spokesman. Barrett, its adviser, said he thinks it’s “very low,” but should ideally be 5 percent to 10 percent.

‘Nuclear Village’

Japan’s biggest nuclear disaster isn’t void of foreign technology. Toshiba, which owns Pennsylvania-based Westinghouse Electric Co., and Hitachi, which has a joint venture with General Electric Co., are tapping American expertise. A giant crane and pulley system supplied by Toshiba to remove spent fuel from the wrecked reactors employs technology developed by Westinghouse.

“We bring in knowledge from foreign companies, organizations and specialists in order to safely decommission the reactors,” Tatsuhiro Yamagishi, spokesman for Tepco, said by email. While the company can’t say the exact number of foreign firms involved in the Fukushima cleanup, companies including Paris-based Areva SA, California-based Kurion Inc. and Massachusetts-based Endeavor Robotics are engaged in work at the site, according to Yamagishi.

For foreign firms, however, independently securing contracts is still a tall order.

“When it comes to Japan’s nuclear industry, the bidding system is completely unclear,” Hiroaki Koide, a former assistant professor at Kyoto University Research Reactor Institute, said in an email. “The system is designed to strengthen the profits of Japan’s nuclear village,” he added, referring to the alliance of pro-nuclear politicians, bureaucrats and power companies that promote reactors.

Tepco’s annual cost to decommission its Fukushima plant may blow out to several hundred billion yen a year, up from the current estimate of ¥80 billion, the trade and industry ministry said in October. As of June, almost ¥1 trillion has been allocated for decommissioning and treating water at Fukushima, according to Tepco’s Yamagishi.

‘Ripe for Corruption’

With that much money at stake, Japan has become ground zero for a plethora of companies looking to benefit from the cleanup work. The structure of Japan’s nuclear industry and the closed procurement preferred by the utilities that operate atomic plants means that the most lucrative opportunities for foreign companies are in the area of subcontracting, according to a report by the EU-Japan Centre for Industrial Cooperation released in March.

“Foreign firms have long argued that the Japanese bidding process is one that is ripe for corruption due to a lack of openness and transparency,” Daniel Aldrich, professor and director of the security and resilience studies program at Northeastern University in Boston, said in an email. For nuclear decommissioning “there is even less clarity and transparency due to security and proliferation concerns,” he said.

Rigging Bids

The Japan Fair Trade Commission raided the offices of five companies last year in relation to rigged bids for maintenance contracts from Tepco, according to Jiji Press. Eleven road-paving companies were fined in September on projects to repair roads following the March 2011 earthquake and tsunami, Jiji reported.

Andrew DeWit, a political economy professor at Rikkyo University in Tokyo, agrees that the contract-awarding process isn’t transparent. A lot of foreign companies seek Japanese partners to better their chances, he said.

Purolite Corp., a closely held water purifying company, spent millions of dollars developing and testing a system that could be used to treat radioactive water at Fukushima. Pennsylvania-based Purolite partnered with Hitachi to help win a contract to use its technology at the wrecked facility.

Those plans didn’t pan out. Purolite is suing Hitachi in New York and Tokyo, alleging that Hitachi is using its technology at Fukushima in breach of agreements made in 2011, shutting it out of more than $1 billion in contracts, according to court documents filed in September.

Hitachi doesn’t comment on ongoing legal matters, a spokesperson said by email.

“With a smaller pool of competitors, firms can expand their profit margins,” said Northeastern University’s Aldrich. “There are French and Russian firms that have the technical expertise to participate in nuclear decommissioning processes, but it is unclear if they will be able to compete on a level playing field with Japanese firms, which have far more experience with Japanese regulations and expectations.” ”

by Stephen Stapczynski, Bloomberg

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Assessing Fukushima damage without eyes on the inside — The New York Times

” A particle that barely ranks as a footnote in a physics text may be about to lift the cleanup of the stricken Fukushima Daiichi nuclear complex in Japan over a crucial obstacle.

Inside the complex, there are three wrecked reactor cores, twisted masses of hundreds of tons of highly radioactive uranium, plutonium, cesium and strontium. After the meltdown, which followed a tsunami and earthquake in 2011, most of the material in the plant’s reactors resolidified, in difficult shapes and in confined spaces, wrapped around and through the structural parts of the reactors and the buildings.

Or at least, that is what the engineers think. Nobody really knows, because nobody has yet examined many of the most important parts of the wreckage. Though three and a half years have passed, it is still too dangerous to climb inside for a look, and sending in a camera would risk more leaks. Engineers do not have enough data to even run a computer model that could tell them how much of the reactor cores are intact and how much of them melted, because the measurement systems inside the buildings were out of commission for days after the accident.

And though the buildings may be leaking, they were built of concrete and steel so thick that there is no hope of using X-rays or other conventional imaging technology to scan the wreckage from a safe distance.

To clean up the reactors, special tools must be custom-made, according to Duncan W. McBranch, the chief technology officer at Los Alamos National Laboratory, and the tools “can be much better designed if you had a good idea of what’s inside.” But “nobody knows what happened inside,” he said. “Nobody wants to go in to find out.”

That is where muons come in.

In the next few days, Toshiba, the contractor in charge of the initial cleanup work, and the laboratory expect to sign a formal agreement to deploy a new technology that experts believe will yield three-dimensional images of the wrecked reactor cores, and will be able to differentiate the uranium and plutonium from other materials, even when 10 feet of concrete and steel are in the way.

The Energy Department has been working on the technology for years, and already licenses it in a less advanced form for a more limited job: A Virginia company is using it in a device that screens shipping containers for smuggled uranium or plutonium that could be used in a nuclear bomb. The lab’s new version will be much more ambitious and will focus on mapping rather than just detection.

The technique takes advantage of the fact that everything on earth is constantly being bombarded by muons, subatomic particles that are somewhat like electrons, though about 200 times as heavy. Muons are shaken loose from molecules in the atmosphere by cosmic radiation. Traveling near the speed of light, they rain down on the earth and can penetrate hundreds of feet into it.

But occasionally, one of the muons will happen to hit an atomic nucleus, and when it does, it will change direction in a way that gives a clue about the shape of the target and the target’s density. The technique of detecting those scattered particles and inferring what it was that they bounced off is called muon tomography.

“There is a similarity to X-ray, but the details of the physics are different,” Dr. McBranch said.

Decision Sciences International, a Virginia company, says it can use muon tomography to screen a 40-foot shipping container in 45 seconds and sense whether there is uranium or plutonium in it, though not in great detail. As altered by the Los Alamos scientists for use at Fukushima, the process requires a much longer exposure — it could take weeks. But the result will be a three-dimensional image; concrete, steel and water will all be distinguishable from uranium, plutonium and other very heavy materials.

“You don’t need a quick image, you just need a good image, and you have plenty of time,” said Stanton D. Sloane, the chief executive of Decision Sciences. Testing will begin later this year, officials say, and final images will be produced next year.

“I would expect to be able to distinguish fairly readily between what would be described as random results from the meltdown, versus engineered structural components,” Mr. Sloane said.

The Department of Energy, which runs the Los Alamos lab, does not yet have a formal agreement with Decision Sciences to produce the necessary hardware, but the company is likely to do so.

Mr. Sloane would not say how much the equipment would cost, but the project is small by nuclear standards. Toshiba will reimburse Los Alamos for its costs, which officials said would come to less than half a million dollars. Los Alamos has spent about $4 million developing the technology. Decision Sciences spent additional money to commercialize it, but has not said how much.

The Los Alamos contribution to the Fukushima project is mostly software. The accompanying apparatus, which has already been tried out on a small, intact reactor, consists of two billboard-size detectors, set up on opposite sides of the building. Each detector is like an array of pipes in a church organ, with each pipe filled with inert gases, including argon, that give an indication when a muon hits. The detectors keep track of which pipes were hit on the way in and on the way out, and at what angle. (It is not possible to “tag” a muon, but by timing the detections, the engineers can tell that they spotted the same muon coming and going.)

The detectors do not have to go inside the reactor building. In fact, they would work less well inside, because gamma radiation coming off the melted fuel would make it harder to spot the muons. Instead, the detectors will be set up a few feet away from the reactor buildings’ outer walls, and will be shielded with four inches of steel, which will stop the gamma rays but makes no difference to the muons.

At sea level, about 10,000 muons will pass through each square meter of the detectors every minute. Only a few of them will be deflected and yield useful data, so the detectors will need to run for weeks to gather enough for a clear picture.

Muon tomography is not completely new; it was used in the 1960s to peer inside the Great Pyramid at Giza. But the current version produces images of much higher resolution, according to Dr. McBranch.

Japan is increasingly turning to other countries for the technology needed to clean up Fukushima. This month, Tepco, the utility that operated the power plant, announced a deal with Kurion, a waste-handling company based in Irvine, Calif., for a mobile system to scrub radioactive strontium from 340,000 tons of contaminated water at the site.

Lake H. Barrett, an engineer who is not directly involved in the muon project, said the technique was certainly worth trying. Mr. Barrett was the director of the Nuclear Regulatory Commission office on site at the cleanup of the Three Mile Island nuclear plant near Harrisburg, Pa.; he is now an adviser to the president of Tepco.

Referring to the technology’s use in detecting smuggled weapons fuel, he said, “It’s nice to see the synergy of nonproliferation technologies, on which we in the U.S. have spent hundreds of millions of dollars, applied to another area.”

“How effective it is, we’ll have to wait and see,” he continued. “But we’re all optimistic.” ”

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Japan lacks decommissioning experts for Fukushima — Phys.org

” Japan is incapable of safely decommissioning the devastated Fukushima nuclear plant alone and must stitch together an international team for the massive undertaking, experts say, but has made only halting progress in that direction.

Unlike the U.S. and some European countries, Japan has never decommissioned a full-fledged reactor. Now it must do so at the Fukushima Dai-Ichi plant. Three of its six reactors melted down after the 2011 earthquake and tsunami, making what is ordinarily a technically challenging operation even more complex.

The cloud over Japan’s capacity to get the decades-long job done has further undermined the image of the nuclear industry with the public. Opinion surveys show a majority of Japanese are opposed to restarting 50 reactors that were put offline for safety and other checks in the aftermath of the disaster. Japan has been forced to import oil and gas to meet its power needs, burdening its already feeble economy.

“Even for the U.S. nuclear industry, such a cleanup and decommissioning would be a great challenge,” said Akira Tokuhiro, a University of Idaho professor of mechanical and nuclear engineering who is among those calling for a larger international role at Fukushima.

Decommissioning a nuclear power plant normally involves first bringing the reactor cores to stable shutdown, and then eventually removing them for long-term storage. It is a process that takes years. Throughout, radiation levels and worker exposure must be monitored.

At Fukushima, there is the daunting challenge of taking out cores that suffered meltdown, which is the most dangerous type of nuclear power accident. Their exact location within the reactor units isn’t known and needs to be ascertained so their condition can be analyzed. That will require development of nimble robots capable of withstanding high radiation.

The lack of experts is worse at the regulatory level. The tally is zero.

Japan’s Nuclear Regulation Authority has no one devoted to decommissioning, said spokesman Juntaro Yamada, though it has experts dealing with the ongoing removal of fuel rods from one of the Fukushima reactor units.

Its predecessor organization was criticized after the Fukushima disaster for being too close to the nuclear industry, so the members chosen for the new agency launched last year don’t have direct ties to the industry to ensure their objectivity.

The government-funded Nuclear Energy Safety Organization, which is to be folded into the regulatory authority to beef up its expertise, has one expert on decommissioning, a person who studies overseas regulations on the process. The group mainly helps with routine nuclear plant inspections, but since the 2011 catastrophe has been involved with bringing the Fukushima plant under control.

In contrast, the U.S. Nuclear Regulatory Commission has 10 people devoted to decommissioning including four project managers, four health physicists, and a hydro-geologist. It says it has the equivalent of more than 200 years of experience in decommissioning and has overseen the termination of 11 power reactors and 13 research reactors.

France has decommissioned nine reactors, and its regulatory agency has seven decommissioning experts at the national level, and 10 more at the local level.

Lake Barrett, a retired nuclear engineer who took part in decommissioning Pennsylvania’s Three Mile Island after the meltdown of its reactor core in 1979, was hired as a consultant by Fukushima operator Tokyo Electric Power Co. He visits about once a year or so to give advice, and is not assigned daily to the job.

The cleanup at Fukushima would be more difficult than Three Mile Island because the damage is more numerous, involving three reactors instead of one, and more serious because of the greater damage from the bigger explosions.

Barrett said one reason he wanted to help Fukushima was that Japanese engineers had helped out at Three Mile Island. He had asked about their whereabouts but got no answers. He fears they are all retired or working in other industries.

“The most challenging area is skilled nuclear engineers and managers that can plan, integrate and communicate effectively in Japanese,” he said.

Japan’s nuclear program started later than the U.S. and it has scrapped only a small test reactor. Five reactors are in various stages of decommissioning, including two experimental reactors and three commercial ones.

The furthest along is Tokai Power Station’s No. 1 reactor, which is 15 years into a planned 22-year process. About 70 experts are working on the decommissioning, but the experience gained with Japan’s oldest reactor is not directly transferable to Fukushima.

The decommissioning of two reactors similar to Fukushima’s began in 2009 at Hamaoka nuclear power plant west of Tokyo, but it is in the early stages and is expected to take nearly 30 more years.

It took until August this year, nearly two and half years after the tsunami, for Japan to set up the International Research Institute for Nuclear Decommissioning, to bring together ideas, both inside and outside Japan, on Fukushima decommissioning and encourage communication.

Tokuhiro, who has more than 20 years in the nuclear design and safety fields, calls it a step in the right direction but too small, given the huge task at hand. The organization acknowledges much remains to be done, including responding to unprecedented challenges that will require the development of robotics and other new technology.

Tokuhiro is advocating the creation of an international team to help Japan, including those with experience at Three Mile Island and Chernobyl in the Ukraine.

“It is clear that this very large undertaking requires an international effort,” he said. “It is in the spirit of a global nuclear energy partnership.” ”

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Uncertainties abound in Fukushima decommissioning — The Associated Press

The Associated Press: ” It’s costly, risky and dependent on technologies that have yet to be fully developed. A decades-long journey filled with unknowns lies ahead for Japan, which took a small step this week toward decommissioning its crippled Fukushima nuclear power plant.

Nobody knows exactly how much fuel melted after the March 2011 earthquake and tsunami knocked out cooling systems. Or where exactly the fuel went – how deep and in what form it is, somewhere at the bottom of reactor Units 1, 2 and 3.

The complexity and magnitude of decommissioning the Fukushima Dai-ichi plant is more challenging than Three Mile Island or Chernobyl, say experts such as Lake Barrett, a former U.S. regulator who directed the Three Mile Island cleanup and now is an outside adviser to Fukushima operator Tokyo Electric Power Co.

One core melted at Three Mile Island in 1979, versus three at Fukushima, and it didn’t leak out of the containment chamber, the outer vessel that houses the reactor core. At Fukushima, multiple hydrogen explosions caused extensive damage, blowing the roofs off three reactor buildings and spewing radiation over a wide area.

Chernobyl was a worse accident in terms of radiation emitted, but authorities chose an easier solution: entombing the facility in cement.

At Fukushima, TEPCO plans a multi-step process that is expected to take 40 years: Painstakingly removing the fuel rods in storage pools, finding and extracting the melted fuel within the broken reactors, demolishing the buildings and decontaminating the soil.

“This is a much more challenging job,” Barrett said during a recent visit to Japan. “Much more complex, more difficult to do.”

Also, water must continuously be channeled into the pools and reactor cores to keep the fuel cool. Tons of contaminated water leaks out of the reactors into their basements, some of it into the ground.

Uncertainty runs high as Japan has never decommissioned a full-size commercial reactor, even one that hasn’t had an accident. TEPCO has earmarked about 1 trillion yen ($10 billion) for the decommissioning, and says it will agree to Prime Minister Shinzo Abe’s request to set aside another 1 trillion yen to fight water leaks.

The government itself has contributed or promised 145 billion yen, and is expected to step up its involvement in the years to come, following criticism over its lack of support and growing concern that the technical and funding challenges are beyond TEPCO’s capabilities.

TEPCO began removing fuel rods Monday from a storage pool at Unit 4, whose building was severely damaged but didn’t have a meltdown because the fuel had been removed from the core for maintenance. In an underwater operation, 22 of the 1,533 sets of fuel rods in a pool on the building’s top floor were transferred to a cask that will be used to move them to safer storage. By 2018, the utility hopes to remove all 3,100 fuel assemblies from storage pools at the four damaged units.

After that would come the real challenge: removing melted or partially melted fuel from the three reactors that had meltdowns, and figuring out how to treat and store it so it won’t heat up and start a nuclear reaction again.

“This is an unprecedented task that nobody in the world has achieved. We still face challenges that must be overcome,” said Hajimu Yamana, a Kyoto University nuclear engineer who heads a government-affiliated agency that is overseeing technological research and development for the cleanup.

Closing the holes and cracks in the containment vessels is the biggest hurdle in the decommissioning process, experts say. Every opening must be found and sealed to establish a closed cooling system. Then, under the current plan, the next step would be to fill the reactor vessels with water and examine the melted fuel.

Because of still fatally high radiation levels, the work will have to rely on remote-controlled robots for years. Scientists are developing robots to spot leaks, monitor radiation levels and carry out decontamination. They are also developing robots that can detect holes and fill them with clay.

Among them is a camera-loaded swimming robot that can go underwater to spot holes and cracks, and another one that can go into ducts and pipes.

Computer simulations show the melted fuel in Unit 1, whose core damage was the most extensive, has breached the bottom of the primary containment vessel and even partially eaten into its concrete foundation, coming within about 30 centimeters (one foot) of leaking into the ground.

“We just can’t be sure until we actually see the inside of the reactors,” Yamana said. “We still need to develop a number of robots and other technology.”

Three Mile Island needed only a few robots, mainly for remote-controlled monitoring, sampling and handling debris, as the melted fuel remained in the core. Manned entry was possible a little more than a year after the accident.

Some experts say Japan’s current decommissioning plan is too ambitious. They counsel waiting until contamination levels come down, and even contemplate building a shell around the reactors for the time being, as at Chernobyl.

“I doubt if Fukushima Dai-ichi’s full decommissioning is possible. Its contamination is so widespread,” said Masashi Goto, a nuclear engineer who designed the Unit 3 reactor and now teaches at Meiji University in Tokyo. “We should not rush the process, because it means more exposure to workers. Instead, we should wait and perhaps even keep it in a cement enclosure.”

Others say the Chernobyl solution wouldn’t be effective, noting that the reactor was a different type without massive water leaks. Developing expertise during the operation is also important to Japan, which has dozens of reactors that face eventual retirement and is considering turning decommissioning into a viable business at home, and possibly in a growing global market.

“If you just put concrete over this, groundwater still will be flowing and things like that, and you have an uncontrolled situation,” Barrett said. “I just don’t see that as a plausible option.”

Only a small test reactor had been successfully scrapped in Japan, with five others now being decommissioned – two experimental and three commercial. The furthest along is Tokai Power Station’s No. 1 reactor, which is 15 years into a planned 22-year process.

Japan also has to worry about future natural disasters.

“There will be many more earthquakes and typhoons,” Goto said. “I hope these plans won’t fail, but we might just have to pray.” “

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Some spent fuel rods at Fukushima were damaged before 2011 disaster — Reuters

” Nov 14 (Reuters) – Three of the spent fuel assemblies due to be carefully plucked from the crippled Japanese nuclear plant at Fukushima in a hazardous year-long operation were damaged even before the 2011 earthquake and tsunami that knocked out the facility.

The plant’s operator, Tokyo Electric Power Co, or Tepco, said the damaged assemblies – 4.5 metre high racks containing 50-70 thin rods of highly irradiated used fuel – can’t be removed from Fukushima’s Reactor No. 4 using the large cask assigned to taking out more than 1,500 of the assemblies.

One of the assemblies was damaged as far back as 1982, when it was mishandled during a transfer, and is bent out of shape, Tepco said in a brief note at the bottom of an 11-page information sheet in August.

In a statement from April 2010, Tepco said it found two other spent fuel racks in the reactor’s cooling pool had what appeared to be wire trapped in them. Rods in those assemblies have pin-hole cracks and are leaking low-level radioactive gases, Tepco spokesman Yoshikazu Nagai told Reuters on Thursday.

The existence of the damaged racks, reported in a Fukushima regional newspaper on Wednesday, came to light as Tepco prepares to begin decommissioning the plant by removing all the spent fuel assemblies from Reactor No. 4.

“The three fuel assemblies … cannot be transported by cask,” Tepco spokeswoman Mayumi Yoshida said in an emailed response to queries on Thursday, referring to the large steel chamber that will be used to shift the fuel assemblies from the pool high up in the damaged reactor building to safe storage.

“We are currently reviewing how to transport these fuel assemblies to the common spent fuel pool,” she said.

Tepco is due within days to begin removing 400 tonnes of the dangerous spent fuel in a hugely delicate and unprecedented operation fraught with risk. Each assembly contains radiation equivalent to around 10 times that of the atomic bomb dropped on Hiroshima in 1945.

Having to deal with the damaged assemblies is likely to make that task more difficult and could jeopardise a 12-month timeframe to complete the removal that many have already called ambitious.

RISKY, COMPLEX OPERATION

Three reactors suffered core meltdowns at the Fukushima Daiichi plant north of Tokyo after the March 2011 disaster that triggered explosions and forced the evacuation of 160,000 people from nearby towns and villages.

Tepco, which has floundered in trying to bring the plant under control in the two and a half years since the disaster, is now moving to full decommissioning at the six-reactor facility.

The most urgent task is to remove the fuel assemblies from the unstable Reactor No. 4, which due to their height – about 18 metres above ground level – are more vulnerable to any new earthquake. The operation is seen as a test of Tepco’s ability to move ahead with decommissioning the whole facility – a task likely to take decades and cost tens of billions of dollars.

Lake Barrett, a former U.S. nuclear regulator who is advising Tepco, visited the Fukushima site on Wednesday and endorsed preparations for the removal of the assemblies.

“While removal of the fuel is usually a routine procedure in operating a power plant, the damage to the reactor building has made the job more complex,” he said, adding he was “genuinely impressed by the thoroughness of the effort and Tepco’s contingency planning.”

Tepco has said the assembly removal process will begin around mid-November, but has not given an exact date, citing what it says are security reasons.

The assemblies must first be lifted from their storage frames in the pool and individually placed in a steel cask – kept all the while under water to prevent overheating. The cask, weighing around 90 tonnes when filled, will then be hoisted by crane from the pool, lowered to ground level and transported by trailer to a common storage pool about 100 metres away. ”

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