High-priced Fukushima ice wall nears completion, but effectiveness doubtful — The Mainichi

” A subterranean ice wall surrounding the nuclear reactors at the stricken Fukushima No. 1 Nuclear Power Plant to block groundwater from flowing in and out of the plant buildings has approached completion.

Initially, the ice wall was lauded as a trump card in controlling radioactively contaminated water at the plant in Fukushima Prefecture, which was crippled by meltdowns in the wake of the March 2011 Great East Japan Earthquake and tsunami. But while 34.5 billion yen from government coffers has already been invested in the wall, doubts remain about its effectiveness. Meanwhile, the issue of water contamination looms over decommissioning work.

In a news conference at the end of July, Naohiro Masuda, president and chief decommissioning officer of Fukushima Daiichi Decontamination & Decommissioning Engineering Co., stated, “We feel that the ice wall is becoming quite effective.” However, he had no articulate answer when pressed for concrete details, stating, “I can’t say how effective.”

The ice wall is created by circulating a coolant with a temperature of minus 30 degrees Celsius through 1,568 pipes that extend to a depth of 30 meters below the surface around the plant’s reactors. The soil around the pipes freezes to form a wall, which is supposed to stop groundwater from flowing into the reactor buildings where it becomes contaminated. A total of 260,000 people have worked on creating the wall. The plant’s operator, Tokyo Electric Power Co. (TEPCO) began freezing soil in March last year, and as of Aug. 15, at least 99 percent of the wall had been completed, leaving just a 7-meter section to be frozen.

Soon after the outbreak of the nuclear disaster, about 400 tons of contaminated water was being produced each day. That figure has now dropped to roughly 130 tons. This is largely due to the introduction of a subdrain system in which water is drawn from about 40 wells around the reactor buildings. As for the ice wall, TEPCO has not provided any concrete information on its effectiveness. An official of the Secretariat of the Nuclear Regulation Authority (NRA) commented, “The subdrain performs the primary role, and the ice wall will probably be effective enough to supplement that.” This indicates that officials have largely backtracked from their designation of the ice wall as an effective means of battling contaminated water, and suggests there is unlikely to be a dramatic decrease in the amount of decontaminated groundwater once the ice wall is fully operational.

TEPCO ordered construction of the ice wall in May 2013 as one of several plans proposed by major construction firms that was selected by the government’s Committee on Countermeasures for Contaminated Water Treatment. In autumn of that year Tokyo was bidding to host the 2020 Olympic and Paralympic Games, and the government sought to come to the fore and underscore its measures to deal with contaminated water on the global stage.

Using taxpayers’ money to cover an incident at a private company raised the possibility of a public backlash. But one official connected with the Committee on Countermeasures for Contaminated Water Treatment commented, “It was accepted that public funds could be spent if those funds were for the ice wall, which was a challenging project that had not been undertaken before.” Small-scale ice walls had been created in the past, but the scale of this one — extending 1.5 kilometers and taking years to complete — was unprecedented.

At first, the government and TEPCO explained that an ice wall could be created more quickly than a wall of clay and other barriers, and that if anything went wrong, the wall could be melted, returning the soil to its original state. However, fears emerged that if the level of groundwater around the reactor buildings drops as a result of the ice wall blocking the groundwater, then tainted water inside the reactor buildings could end up at a higher level, causing it to leak outside the building. Officials decided to freeze the soil in stages to measure the effects and effectiveness of the ice wall. As a result, full-scale operation of the wall — originally slated for fiscal 2015 — has been significantly delayed.

Furthermore, during screening by the NRA, which had approved the project, experts raised doubts about how effective the ice wall would be in blocking groundwater. The ironic reason for approving its full-scale operation, in the words of NRA acting head Toyoshi Fuketa, was that, “It has not been effective in blocking water, so we can go ahead with freezing with peace of mind” — without worrying that the level of groundwater surrounding the reactor buildings will decrease, causing the contaminated water inside to flow out.

Maintaining the ice wall will cost over a billion yen a year, and the radiation exposure of workers involved in its maintenance is high. Meanwhile, there are no immediate prospects of being able to repair the basement damage in the reactor buildings at the crippled nuclear plant.

Nagoya University professor emeritus Akira Asaoka commented, “The way things stand, we’ll have to keep maintaining an ice wall that isn’t very effective. We should consider a different type of wall.”

In the meantime, TEPCO continues to be plagued over what to do with treated water at the plant. Tainted water is treated using TEPCO’s multi-nuclide removal equipment to remove 62 types of radioactive substances, but in principle, tritium cannot be removed during this process. Tritium is produced in nature through cosmic rays, and nuclear facilities around the world release it into the sea. The NRA takes the view that there is no problem with releasing treated water into the sea, but there is strong resistance to such a move, mainly from local fishing workers who are concerned about consumer fears that could damage their businesses. TEPCO has built tanks on the grounds of the Fukushima No. 1 plant to hold treated water, and the amount they hold is approaching 800,000 metric tons.

In mid-July, TEPCO Chairman Takashi Kawamura said in an interview with several news organizations that a decision to release the treated water into the sea had “already been made.” A Kyodo News report on his comment stirred a backlash from members of the fishing industry. TEPCO responded with an explanation that the chairman was not stating a course of action, but was merely agreeing with the view of the NRA that there were no problems scientifically with releasing the treated water. However, the anger from his comment has not subsided.

Critical opinions emerged in a subsequent meeting that the Ministry of Economy, Trade and Industry held in the Fukushima Prefecture city of Iwaki at the end of July regarding the decontamination of reactors and the handling of contaminated water. It was pointed out that prefectural residents had united to combat consumer fears and that they wanted officials to act with care. One participant asked whether the TEPCO chairman really knew about Fukushima.

The ministry has been considering ways to handle the treated water, setting up a committee in November last year that includes experts on risk evaluation and sociology. As of Aug. 15, five meetings had been held, but officials have yet to converge on a single opinion. “It’s not that easy for us to say, ‘Please let us release it.’ It will probably take some time to reach a conclusion,” a government official commented. “

by The Mainichi

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Minister opposes releasing treated water from Fukushima plant into sea — The Mainichi

According to The Georgia Straight, plans to dump tritium-contaminated waste water into the Pacific Ocean have been cancelled.

The Mainichi: ” TOKYO (Kyodo) — Japan’s disaster reconstruction minister said Friday he is opposed to treated water from the disaster-struck Fukushima Daiichi nuclear power plant being released into the sea, citing the possible repercussions for local fishermen.

Masayoshi Yoshino’s remarks came shortly after a top official from plant operator Tokyo Electric Power Company Holdings Inc. said he is ready to see the tritium-containing water dumped into the sea.

A government panel is still debating how to deal with the water stored in tanks at the plant where three nuclear reactors melted down in the days after a huge earthquake and then tsunami struck the region in 2011.

Tritium is a radioactive substance considered relatively harmless to humans. It remains in the filtered water as it is difficult to separate even after passing through a treatment process. At other nuclear power plants, tritium-containing water is routinely released into the sea after it is diluted.

Yoshino expressed at a news conference his concerns over the potential ramifications of releasing the treated water into the sea, saying there would “certainly be (perception) damage due to unfounded rumors.”

The minister urged those pushing for the release of the water “not to create fresh concerns for fishermen and those running fishing operations in Fukushima Prefecture.” He also asked them “not to drive (fishermen) further towards the edge.”

He was alluding to concerns among local fishermen about the effects on their livelihood if the public perceives fish and other marine products caught off Fukushima to be contaminated.

Takashi Kawamura, chairman of Tepco, said in a recent interview that the decision to discharge the treated water “has already been made.”

After Kawamura’s remarks were widely reported, the utility was forced to make a clarification through a statement on Friday. Tepco said its chairman meant to say there is “no problem (with releasing water containing tritium) according to state guidelines based on scientific and technological standpoints,” and that the decision to release is not yet final.

While the plant operator and the Ministry of Economy, Trade and Industry want to discharge the water, the local fishermen, backed by the minister, are opposed to it.

At the Fukushima plant, water becomes toxic when it is used to cool the damaged reactors. It is treated through a process said to be capable of removing 62 different types of radioactive material, except tritium.

Yoshino said Friday that while he is aware of some scientists’ opinion that the water should be released after it is diluted to permissible levels, he is not in favor of the idea.

“As I am also a native of Fukushima Prefecture, I fully understand the sentiment of the people,” Yoshino said. However, the minister has no authority to decide how the treated water will be disposed.

An ever-increasing amount of water containing tritium is collecting in tanks at the Fukushima plant. As of July 6, approximately 777,000 tons were stored in about 580 tanks.

On March 11, 2011, water inundated the six-reactor plant, located on ground 10 meters above sea level, and flooded power supply facilities. Reactor cooling systems were crippled and the Nos. 1 to 3 reactors suffered fuel meltdowns in the world’s worst nuclear catastrophe since the 1986 Chernobyl disaster. “

by The Mainichi

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Fishermen express fury as Fukushima plant set to release radioactive material into ocean — The Telegraph

” Local residents and environmental groups have condemned a plan to release radioactive tritium from the crippled Fukushima nuclear plant into the Pacific Ocean.

Officials of Tokyo Electric Power Co., the operator of the plant, say tritium poses little risk to human health and is quickly diluted by the ocean.

In an interview with local media, Takashi Kawamura, chairman of TEPCO, said: “The decision has already been made.” He added, however, that the utility is waiting for approval from the Japanese government before going ahead with the plan and is seeking the understanding of local residents.

The tritium is building up in water that has been used to cool three reactors that suffered fuel melt-downs after cooling equipment was destroyed in the magnitude 9 earthquake and tsunami that struck north-east Japan in March 2011.

Around 770,000 tons of highly radioactive water is being stored in 580 tanks at the site. Many of the contaminants can be filtered out, but the technology does not presently exist to remove tritium from water.

“This accident happened more than six years ago and the authorities should have been able to devise a way to remove the tritium instead of simply announcing that they are going to dump it into the ocean”, said Aileen Mioko-Smith, an anti-nuclear campaigner with Kyoto-based Green Action Japan.

“They say that it will be safe because the ocean is large so it will be diluted, but that sets a precedent that can be copied, essentially permitting anyone to dump nuclear waste into our seas”, she told The Telegraph.

Fishermen who operate in waters off the plant say any release of radioactive material will devastate an industry that is still struggling to recover from the initial nuclear disaster.

“Releasing [tritium] into the sea will create a new wave of unfounded rumours, making all our efforts for naught”, Kanji Tachiya, head of a local fishing cooperative, told Kyodo News. ”

by Julian Ryall, The Telegraph

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High levels of cesium radioactive material migrating down into soil around Fukushima — Global Research

” High levels of radioactive cesium remain in the soil near the Fukushima Daiichi nuclear power plant and these radionuclides have migrated at least 5 centimeters down into the ground at several areas since the nuclear accident five years ago, according to preliminary results of a massive sampling project being presented at the JpGU-AGU joint meeting in Chiba, Japan.

In 2016, a team of more than 170 researchers from the Japanese Geoscience Union and the Japan Society of Nuclear and Radiochemical Sciences conducted a large-scale soil sampling project to determine the contamination status and transition process of radioactive cesium five years after a major earthquake and tsunami caused a nuclear accident at the Fukushima Daiichi plant.

The team collected soil samples at 105 locations up to 40 kilometers (25 miles) northwest of the Fukushima Daiichi nuclear power plant in the “difficult-to-return” zone where entry is prohibited. The project seeks to understand the chemical and physical forms of radionuclides in the soil and their horizontal and vertical distribution.

The Japanese government has monitored the state of radioactive contamination in the area near the plant since the 2011 accident by measuring the air dose rate, but scientists can only determine the actual state of contamination in the soil and its chemical and physical forms by direct soil sampling, said Kazuyuki Kita, a professor at Ibaraki University in Japan, who is one of the leaders of the soil sampling effort.

Understanding the radionuclides’ chemical and physical forms helps scientists understand how long they could stay in the soil and the risk they pose to humans, plants and animals, Kita said. The new information could help in assessing the long-term risk of the radionuclides in the soil, and inform decontamination efforts in heavily contaminated areas, according to Kita, one of several researchers will present the team’s preliminary results at the JpGU-AGU joint meeting next week.

Preliminary results show high levels radioactive cesium are still present in the soil near the plant. The levels of radiation are more than 90 percent, on average, of what was found immediately following the accident, according to Kita.

Most of the radiocesium in the soil was found near the surface, down to about 2 centimeters, immediately following the 2011 accident. Five years later, at several sampling points, one-third to one-half of the radiocesium has migrated deeper into the soil, according to Kita. Preliminary results show the radiocesium moved about 0.3 centimeters per year, on average, deeper into the soil and soil samples show the radiocesium has penetrated at least 5 centimeters into the ground at several areas, according to Kita.

The team plans to analyze samples taken at greater depths to see if the radiocesium has migrated even further, he said.

“Most of the radioactive cesium remains after five years, but some parts of the radioactive cesium went from the surface to deeper soil,” he said.

Knowing how much radioactive contamination has stayed on the surface and how deep it has penetrated into the soil helps estimate the risk of the contaminants and determine how much soil should be removed for decontamination. The preliminary results suggest decontamination efforts should remove at least the top 6 to 8 centimeters of soil, Kita said.

The preliminary data also show there are insoluble particles with very high levels of radioactivity on the surface of the soil. Debris from the explosion fused with radiocesium to form small glass particles a few microns to 100 microns in diameter that remain on the ground, according to Kita. The team is currently trying to determine how many of these radiocesium glass particles exist in areas near the nuclear plant, he said.

“We are afraid that if such high radioactive balls remain on the surface, that could be a risk for the environment,” Kita said. “If the radioactivity goes deep into the soil, the risk for people in the area decreases but we are afraid the high radioactive balls remain on the surface.” “

by Nancy Bompey, Global Research

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Japan seeks final resting place for highly radioactive nuclear waste — Deutsche Welle

” With communities refusing to come forward to host the by-product of Japan’s nuclear energy industry, the Japanese government is drawing up a map of the most suitable locations for underground repositories.

The Japanese government is putting the finishing touches to a map of the country identifying what its experts consider to be the safest location for a repository for 18,000 tons of highly radioactive nuclear waste for the next 100,000 years. The map is expected to be released next month and will coincide with the government holding a series of symposiums across the country designed to explain why the repository is needed and to win support for the project.

Given that the disaster at the Fukushima Dai-ichi nuclear plant in March 2011 is still fresh in the memory of the Japanese public, the government’s plan is not expected to win much understanding or support.

The original proposal for a repository for the waste from the nation’s nuclear energy sector was first put forward in 2002, but even then there were few communities that were willing to be associated with the dump. Fifteen years later, and with a number of Japan’s nuclear reactors closed down for good in the wake of the Fukushima accident, the need for a permanent storage site is more pressing than ever.

Radioactivity release

The disaster, in which a 13-meter tsunami triggered by an off-shore earthquake crippled four reactors at the plant and caused massive amounts of radioactivity to escape into the atmosphere, also underlined just how seismically unstable the Japanese archipelago is and the need for the repository to be completely safe for 100,000 years.

Aileen Mioko-Smith, an anti-nuclear campaigner with Kyoto-based Green Action Japan, does not believe the government can deliver that guarantee.

“You only have to look at what happened in 2011 to realize that nowhere in Japan is safe from this sort of natural disaster and it is crazy to think otherwise,” she told DW.

Given the degree of public hostility, Mioko-Smith believes that the government will fall back on the tried-and-trusted tactic of offering ever-increasing amounts of money until a community gives in.

Government funds

“They have been trying to get this plan of the ground for years and one thing they tried was to offer money to any town or village that agreed to even undergo a survey to see if their location was suitable,” she said.

“There were a number of mayors who accepted the proposal because they wanted the money – even though they had no intention of ever agreeing to host the storage site – but the backlash from their constituents was fast and it was furious,” Smith added.

“In every case, those mayors reversed their decisions and the government has got nowhere,” she said. “But I fear that means that sooner or later they are just going to make a decision on a site and order the community to accept it.”

The security requirements of the facility will be exacting, the government has stated, and the site will need to be at least 300 meters beneath the surface in a part of the country that is not subject to seismic activity from active faults or volcanoes. It must also be safe from the effects of erosion and away from oil and coal fields. Another consideration is access and sites within 20 km of the coast are preferred.

High-level waste

The facility will need to be able to hold 25,000 canisters of vitrified high-level waste, while more waste will be produced as the nation’s nuclear reactors are slowly brought back online after being mothballed since 2011 for extensive assessments of their safety and ability to withstand a natural disaster on the same scale as the magnitude-9 earthquake that struck Fukushima.

Stephen Nagy, a senior associate professor of international relations at Tokyo’s International Christian University, agrees that the government will have to pay to convince any community to host the facility.

“They will probably peddle it as subsidies for rural revitalization, which is a tactic that all governments use, but there are going to be some significant protests because Fukushima has created a nuclear allergy in most people in Japan,” he said.

“I expect that the government would also very much like to be able to phase out nuclear energy, but that is simply not realistic at the moment,” he said.

When it is released, the government’s list is likely to include places in Tohoku and Hokkaido as among the most suitable sites, because both are relatively less populated than central areas of the country and are in need of revitalization efforts. Parts of Tohoku close to the Fukushima plant may eventually be chosen because they are still heavily contaminated with radiation from the accident. ”

by Deutsche Welle

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Finding and removing melted fuel rods at Fukushima No. 1 — Nikkei Asian Review, The Japan Times

Nikkei Asian Review, “Survey fails to find melted rods at Fukushima reactors”:

” TOKYO — A remote survey of the Fukushima Daiichi nuclear plant’s No. 1 reactor was unable to locate and photograph melted nuclear fuel, Tokyo Electric Power Co. Holdings said Thursday, complicating efforts to remove that material as part of an extensive cleanup.

Tepco on Saturday sent a robot equipped with a camera into the containment vessel for the No. 1 unit. The majority of fuel rods have melted through the unit’s pressure vessel since the plant was struck by the March 11, 2011, earthquake and tsunami. The prevailing view has been that those melted fuel rods are now sitting under 2.5m of water at the bottom of the containment vessel.

The plan was to explore the bottom section by dipping a camera into the pool of water for the first time. But unexpected barriers such as pipes kept the camera around 1 meter from the bottom in most of the 10 positions surveyed instead of the intended depth of about 40cm from the bottom. While the camera was able to capture sand-like sediment, there was no trace of the melted fuel rods. Adding a fifth day to the investigation turned up no further evidence.

Yuichi Okamura, acting general manager of Tepco’s onsite nuclear power division, offered few comments at the utility’s Thursday news conference, saying only that “photographs and radiation data will need to be evaluated in conjunction with one another.”

The timeline set by Tepco and the government for decommissioning the Fukushima plant aims to begin extraction of melted-down material from the No. 1, No. 2 or No. 3 reactor in 2021 or earlier. An extraction plan is to be decided this summer. But the fact that the status of the melted rods still remains unknown underscores the seriousness of the accident.

The results of the robot survey were “limited,” according to Masanori Naitoh, director of nuclear safety analysis at the Institute of Applied Energy’s Nuclear Power Engineering Center. “It would be difficult to set a plan for extraction based on the information from this survey alone.”

An investigation of the No. 2 reactor also fell short, with the survey robot unable to reach the targeted spot right under the unit’s pressure vessel. ”

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The Japan Times, “Tepco’s biggest hurdle: How to remove melted fuel from crippled Fukushima reactors”:

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

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

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

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

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

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

In search of melted fuel

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

The images showed black lumps scattered beneath the pressure vessel.

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

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

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

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

Radiation barrier

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

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

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

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

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

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

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

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

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

Fuel removal strategy

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

To remove or not

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

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

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

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

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

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

by Kazuaki Nagata

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