Tepco finishes nuclear fuel removal from Fukushima reactor pool
The Fukushima No. 1 nuclear plant’s No. 3 reactor
Feb 28, 2021
Tokyo Electric Power Company Holdings Inc. said Sunday it has removed all 566 nuclear fuel assemblies from the spent fuel pool of the No. 3 reactor at its Fukushima No. 1 plant.
It is the first time that fuel removal has been completed for any of the three reactors that suffered meltdowns in the March 2011 accident at the plant in Fukushima Prefecture.
The fuel removal operation at the No. 3 reactor began in April 2019.
On Sunday, the company using remote control devices moved the last six assemblies to a common storage facility within the plant premises. A large covering was placed over the upper part of the No. 3 reactor building to prevent radioactive substances from being scattered.
Tepco planned to start the fuel removal from the No. 3 reactor building as early as late 2014, but delayed the schedule repeatedly as it faced difficulty getting rid of debris left by the explosion in the building.
The operation also took more time than expected due to machinery malfunction issues.
The removal of 1,533 fuel assemblies from the No. 4 reactor building was completed in December 2014.
Tepco aims to finish pulling all fuel assemblies out of other reactor buildings by the end of 2031, including the No. 1 building, where a lot of debris is scattered about, and the No. 2 building, where radiation levels are particularly high.https://www.japantimes.co.jp/news/2021/02/28/national/tepco-fukushima-no-1-radiation-3-11-tsunami-earthquakes-fukushima/
All spent fuel finally removed from reactor at Fukushima plant
Steel frames remain exposed on the wall facing north at the No. 3 reactor building at the Fukushima No. 1 nuclear plant, showing the impact from a hydrogen explosion in March 2011.
February 28, 2021
Hazardous work to remove all spent nuclear fuel from a reactor storage pool at the crippled Fukushima No. 1 nuclear plant was finally completed Feb. 28, Tokyo Electric Power Co. said.
It marked the first time for any of the storage pools at the three stricken reactors to be emptied out, and came less than two weeks before the 10th anniversary of the triple meltdown at the nuclear complex in Fukushima Prefecture northeast of Tokyo.
The two-year effort involved the removal of all the 566 spent fuel units left in the pool in the No. 3 reactor’s building.
Completion of the removal work at the No. 3 reactor building, severely damaged by a hydrogen explosion during the meltdown, eased concerns about the overall safety of the embattled plant.
The No. 3 reactor’s storage pool is situated on an upper floor of the building, posing a danger due to fears of another powerful earthquake damaging the structure and jeopardizing TEPCO’s ability to cool them.
Spent fuel needs to be kept cool as it emits high levels of radiation and decaying heat.
The utility planned to move the spent fuel from the No. 3 reactor’s pool to a shared pool for storage on the grounds of the plant to ensure the spent fuel can be safely managed.
The removal work got under way in April 2019 after rubble and other debris were cleared away. A special crane with a robotic arm was used to lift the spent fuel.
Operators worked remotely during the removal process from an operational center 500 meters away because of high radiation readings inside the reactor building.
The work was marred by a flurry of malfunctions in the equipment and the crane soon after the project got started.
The challenge was further complicated by rubble and debris in the pool that distorted the handles of some of the spent fuel units.
During the last stretch of the removal work, operators picked up the pace by working in shifts around the clock.
The remaining six units were transferred to the shared pool on Feb. 28. The development came roughly three years after the government and TEPCO announced an initial roadmap for the work in December 2011.
The removal of spent fuel from the No. 4 reactor building was completed in late 2014. The No. 4 reactor had been shut down for maintenance prior to the disaster triggered by the Great East Japan Earthquake and tsunami in 2011.
With regard to the No. 1 and No. 2 reactors, which went in meltdown after the quake and tsunami disaster knocked out cooling systems, a combined 1,000 spent fuel units remain in their storage pools.
TEPCO is aiming at starting the removal work at the two reactors in fiscal 2024 or beyond.
Apart from the spent fuel, 800 to 900 tons of melted nuclear fuel remain in the No. 1 through No. 3 reactors.
Last 6 assemblies Stored in Containers; Nuclear Fuel Removal from Unit 3 Pool at Fukushima Daiichi Nuclear Power Plant to End
Nuclear fuel being lifted by a fuel handling machine. A monitor screen shows a lot of small debris in the pool, at Tokyo Electric Power Co.’s Fukushima Daiichi Nuclear Power Plant in Okuma, Fukushima Prefecture, April 15, 2019.
February 26, 2021
The Tokyo Electric Power Company (TEPCO) stored the last six nuclear fuels in special containers in the spent fuel pool at the Unit 3 reactor of the Fukushima Daiichi Nuclear Power Plant on April 26. Although the work began in April 2019, it will be completed earlier than the target of the end of March 2021. A total of 566 nuclear fuels, 514 spent and 52 unused, were stored in the pool. (Shinichi Ogawa)
This is the second reactor to have nuclear fuel removed from its spent fuel pool, following the Unit 4 reactor (1,535 nuclear fuels) which finished in December 2014. This is the first time for Units 1-3, which suffered a core meltdown (meltdown).
The initial plan was to start removing the nuclear fuel from the Unit 3 reactor by the end of 2002, but the high radiation dose became a barrier to the work. A dome-shaped cover was installed on top of the building to prevent radioactive materials from spreading outside. TEPCO had indicated plans to start removing the radioactive materials in November 2006, but due to a series of problems with cranes and other equipment, the work was postponed for inspection and replacement of parts.
According to the plan presented by the government and TEPCO, the removal of nuclear fuel from the pool is scheduled to start in FY2015-28 for Unit 1 (392 nuclear fuels) and in FY2012-26 for Unit 2 (615 nuclear fuels).
TEPCO to start removing fuel at Fukushima’s No. 3 reactor
Fuel removal from Fukushima reactor may be delayed
TEPCO prepares to remove fuel from damaged reactor
Fukushima dome roof takes shape, but radiation remains high
Preparations to unload reactor 3’s pool
On November 8th two machines arrived at Fukushima Daiichi : a bridge crane and a fuel handling machine. These two machines will be installed on the reactor 3’s platform in order to unload the pool of its fuel.
Source: Pierre Fetet http://www.fukushima-blog.com/
Multiple challenges remain to Fukushima nuclear cleanup
This Sept. 4, 2017 aerial photo shows Fukushima Dai-ichi nuclear power plant reactors, from bottom at right, Unit 1, Unit 2 and Unit 3, in Okuma, Fukushima Prefecture, northeastern Japan. The three reactors that had meltdowns together have 1,573 units of mostly used nuclear fuel rods that are still inside and must be kept cool in pools of water. They are considered among the highest risks in the event of another major earthquake, because the pools are uncovered. The plant operator, Tokyo Electric Power Co. or TEPCO, plans to begin removing the rods from reactor unit 3 in the fiscal year beginning next April 1. However, the latest roadmap delays removal of the rods from units 1 and 2 for three years until fiscal 2023, because further decontamination work and additional safety measures are needed.
Japan’s government approved on Tuesday, Sept. 26, 2017 a revision to the decommissioning plan for the Fukushima nuclear plant, delaying by two more years the removal of radioactive fuel rods in two of the three reactors damaged in the 2011 disaster. It still plans for melted fuel to be removed starting in 2021, but the lack of details about the duration raises doubts if the cleanup can be completed within 40 years. Kyodo News via AP, File)
TOKYO – Japan’s government approved a revised road map Tuesday to clean up the radioactive mess left at the Fukushima nuclear power plant after it was damaged beyond repair by an earthquake and tsunami in 2011. Decommissioning the damaged reactors is an uncertain process that is expected to take 30 to 40 years.
A look at some of the challenges:
THE FUEL RODS
The three reactors that had meltdowns together have 1,573 units of mostly used nuclear fuel rods that are still inside and must be kept cool in pools of water. They are considered among the highest risks in the event of another major earthquake that could trigger fuel rods to melt and release massive radiation due to loss of water from sloshing or structural damage because the pools are uncovered. The plant operator, Tokyo Electric Power Co., or TEPCO, plans to begin moving the rods from reactor Unit 3 in the fiscal year beginning April 1.
However, the latest road map delays removal of the rods from units 1 and 2 for three years until fiscal 2023, because further decontamination work and additional safety measures are needed. Ironically, because the building housing reactor 3 was more heavily damaged, it is easier to remove that unit’s fuel rods. The fuel rods will be moved to a storage pool outside the reactors, and eventually sent for long-term storage in what are known as dry casks.
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THE MELTED FUEL
By far the hardest part of decommissioning Fukushima will be removing the fuel that melted and presumably spilled out of the reactor cores. In July, an underwater robot for the first time captured images inside the primary containment chamber of Unit 3. They showed a large number of solidified lava-like rocks and lumps on the chamber’s floor, believed to be melted fuel mixed with melted and mangled equipment and parts of the structure.
The search for melted fuel in units 1 and 2 has so far been unsuccessful. The water level is lower, so crawling robots have been tried, but they have been obstructed by debris as well as extremely high radiation levels. Despite the unknowns about the melted fuel and debris and their whereabouts, the road map calls for finalizing the removal method in 2019, and starting actual removal at one of the reactors in 2021. The government-funded International Research Institute for Nuclear Decommissioning is developing robots and other technology to carry out the work.
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CONTAMINATED WATER
TEPCO has treated and stored a massive amount of radioactive water — about 800,000 tons — and the volume is growing every day. Cooling water leaks out of the damaged reactors and mixes with groundwater that seeps into the basements of the reactor building, increasing the amount of contaminated water. The utility has managed to halve the volume to 200 tons per day by pumping up groundwater via dozens of wells dug upstream from the reactors, as well as installing a costly “ice wall” by freezing the ground to block some of the water from coming in and going out.
The water is stored in hundreds of tanks that cover much of the plant property. They get in the way of decommissioning work and pose another risk if they were to spill out their contents in another major earthquake or tsunami. After treatment, the water still contains radioactive tritium, which cannot be removed but is not considered harmful in small amounts. Experts say controlled release of the water into the ocean is the only realistic option, but TEPCO has not moved forward with that plan because of opposition from fishermen and residents who fear a negative image and possible health impact.
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RADIOACTIVE WASTE
Japan has yet to develop a plan to dispose of the highly radioactive waste that will come out of the Fukushima reactors. Under the road map, the government and TEPCO will compile a basic plan during fiscal 2018. Managing the waste will require new technologies to compact it and reduce its toxicity. Finding a storage site for the waste seems virtually impossible, as the government has not been able to find a site even for the normal radioactive waste from its nuclear power plants. The prospect raises doubts about whether the cleanup can really be completed within 40 years.
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http://www.miamiherald.com/news/business/article175387901.html
Spent Nuclear Fuel Removal at Fukushima Plant Delayed Again
Japan muddles on with Fukushima’s melted and “spent” fuel. The three year delay for emptying the reactors “spent” irradiated nuclear fuel into a dry cask storage runs the risk of another major earthquake causing a loss of cooling in the pools without containments and another major release of radiation. Plans for removing the melted reactor cores from Units 1, 2 and 3 still defied by inability to locate it.
Fukushima Nuclear Plant Scrapping Plan Faces Another Delay
A key decision in decommissioning the crippled Fukushima Daiichi nuclear plant is being delayed. The Japanese government and operator made the announcement on Tuesday while giving an update on the roadmap for scrapping the plant.
In their first such update in 2 years, officials said they will postpone their decision on the method for removing molten fuel debris by one year, until fiscal 2019.
Experts believe that when the plant went into triple meltdown in 2011, most of the fuel inside the reactors collected at the bottom of containment vessels. They still don’t know the exact location, but possible molten fuel debris was caught on camera in July. The removal of this debris is considered the most challenging part of the plant’s decommissioning.
Originally, officials considered filling the containment vessels with water to block radiation while removing the debris. But now, they say they’re leaning towards a method called dry removal.
Experts say that method comes with safety challenges. “Because the containment vessel will not be filled with water, there is a possibility that radioactive substances may leak and get dispersed,” says Hosei University Visiting Professor Hiroshi Miyano.
Officials also gave an update on plans for the removal of spent nuclear fuel rods in 2 of the plants reactors. The rods are in storage pools and won’t be removed until fiscal 2023. That’s 3 years later than planned. The official timeline for scrapping the plant remains the same — about 30 to 40 years in total.
https://www3.nhk.or.jp/nhkworld/nhknewsline/nuclearwatch/fukushimanuclearplantscrapping/
Spent nuclear fuel removal at Fukushima plant pushed back again
Cabinet ministers attend a meeting at the Prime Minister’s Office on Tuesday to discuss a delay in the road map for decommissioning the Fukushima No. 1 nuclear power plant.
The government and Tokyo Electric Power Company Holdings Inc. decided Tuesday to further delay the removal of spent nuclear fuel left near two of the three reactors that suffered meltdowns at the Fukushima No. 1 nuclear plant.
In the road map for decommissioning the plant, revised for the fourth time since it was first crafted in 2011, highly radioactive spent fuel will be extracted from the cooling pools of reactors 1 and 2 starting in fiscal 2023 instead of fiscal 2020.
The decision marks the third delay for the removal plan, with the last adjustment coming in June 2015. The government said new technical issues and the need to take safety precautions led to the latest change.
The cleanup process is set to be completed in around 30 to 40 years.
Spent fuel removal at the plant’s reactor 3 will go ahead in fiscal 2018 as planned, having already been pushed back earlier this year.
In the decommissioning process, the removal of fuel rod assemblies from the spent fuel pools in reactor buildings is one of the key steps before extracting melted fuel debris. Reactors 1, 2 and 3 suffered core meltdowns following the March 2011 earthquake and tsunami disaster.
The removal of melted fuel debris has also been delayed, with an extraction plan set to be decided in fiscal 2019, pushed back from the first half of fiscal 2018.
Despite the delay in finalizing specific methods, the road map maintains a 2021 start for debris extraction, the most challenging part of the decommissioning process.
A method currently considered feasible by the government involves removing debris from the sides of the reactors after partially filling them with water.
The road map newly sets the goal of cutting the amount of underground water at the plant to address contaminated water buildup. Underground water — which gets mixed with accumulated radioactive water generated in the process of cooling the damaged reactors — is to be cut to around 150 tons per day in 2020 from the current 200 tons.
The road map does not mention a specific schedule for the disposal of processed water that still contains radioactive tritium.
The plan was first crafted in December 2011 in the wake of the meltdowns, the world’s worst nuclear crisis since the 1986 Chernobyl disaster.
Attempts have been made to confirm the situation inside the damaged reactors using specialized robots. A survey in July this year captured for the first time images of what is likely to be melted nuclear fuel at the bottom of reactor 3.
Isamu Kaneda, deputy mayor of the Fukushima Prefecture town of Futaba, expressed regret over the delay.
“The town’s rebuilding depends on the development of decommissioning. It’s unfortunate,” Kaneda said. “But at the same time, the decommissioning process is an unprecedented project. It needs to be conducted carefully, so we can’t just ask them to speed it up.”
Spent nuclear fuel removal at Fukushima plant to be delayed again
TOKYO (Kyodo) — The government and Tokyo Electric Power Company Holdings Inc. decided Tuesday to delay again the start of removing spent nuclear fuel left near two of the three reactors which suffered a meltdown at the Fukushima complex.
In the road map for decommissioning the Fukushima Daiichi plant, revised for the fourth time since it was first crafted in December 2011, highly radioactive spent nuclear fuel will be extracted from the Nos. 1 and 2 units’ cooling pools starting in fiscal 2023 instead of fiscal 2020.
It is the third time that the schedule for spent fuel removal has been pushed back at the Nos. 1 and 2 reactors, with the previous postponement taking place in June 2015. The government said new technical issues and the need to take safety precautions led to the latest schedule change.
The cleanup process is to be completed in around 30 to 40 years.
For the No. 3 reactor at the Fukushima plant, the schedule to remove spent nuclear fuel during fiscal 2018 is unchanged after having already been pushed back earlier this year.
In the decommissioning process, taking out fuel rod assemblies from the spent fuel pools inside reactor buildings is one of the key steps before extracting melted fuel debris from the Nos. 1 to 3 reactors, all of which suffered core meltdowns following the March 2011 earthquake and tsunami disaster.
The schedule for extraction of the melted fuel debris at the reactors was also revised, with the determination of a specific approach to remove the debris to be made in fiscal 2019, rather than in the originally planned first half of fiscal 2018.
Despite the delay in finalizing specific methods, the road map kept the start of the debris extraction, the most challenging part of the decommissioning process, at 2021.
A method currently considered feasible by the government is debris removal from the side of the three crippled reactors by partially filling them with water.
The road map newly sets the goal of cutting the amount of underground water at the plant to address contaminated water buildup at the site. Underground water, which gets mixed with accumulated radioactive water generated in the process of cooling the damaged reactors — is to be cut to around 150 tons per day in 2020 from the current 200 tons.
It did not mention a specific schedule for disposal of processed water that still contains radioactive tritium.
The road map was first crafted in December 2011 in the wake of the 2011 disaster which triggered at the Fukushima plant the world’s worst nuclear crisis since the 1986 Chernobyl disaster.
Attempts have been made to confirm internal conditions of the damaged reactors using robots. A survey robot captured images of what is likely to be melted nuclear fuel at the bottom of the No. 3 reactor for the first time in July this year.
http://mainichi.jp/english/articles/20170926/p2g/00m/0dm/064000c
TEPCO to delay emptying fuel storage pools at Fukushima plant
The No. 1 reactor building, left, and the No. 2 reactor building at the crippled Fukushima No. 1 nuclear plant
Plans to remove fuel rods from two spent fuel pools at the Fukushima No. 1 nuclear plant will be delayed by up to three years because of difficulties in clearing debris and reducing radiation levels.
The government and plant operator Tokyo Electric Power Co. originally expected to start emptying the storage pools at the No. 1 and No. 2 reactor buildings in fiscal 2020.
But they plan to move the starting time to fiscal 2023 in their first review in two years of the roadmap for decommissioning the stricken nuclear plant, sources said Sept. 20.
They are expected to announce the revised roadmap later this month.
A survey of the upper levels of the two reactor buildings, where the storage pools are located, found debris piled up in a much more complicated way than initially envisaged.
That will lengthen the time needed to clear the debris, thus delaying the removal of the fuel rods, the sources said.
In addition, radiation levels remain extremely high inside the buildings.
The No. 1 reactor’s storage pool holds 392 nuclear fuel assemblies, while the No. 2 reactor’s pool has 615 assemblies.
Work to remove the 566 assemblies from the No. 3 reactor’s pool is scheduled to begin in the middle of fiscal 2018 as originally planned.
The three reactors melted down in the 2011 disaster, triggered by the magnitude-9.0 Great East Japan Earthquake and tsunami.
The review of the decommissioning roadmap is also expected to revise the target of “starting the removal” of melted nuclear fuel and debris in the three reactors in 2021 to “aiming to start the removal” in 2021.
But the government and TEPCO will maintain the goal of completing the decommissioning in “30 to 40 years,” the sources said.
Tepco’s biggest hurdle: How to remove melted fuel from crippled Fukushima reactors
Tepco’s scorpion-shaped robot. | IRID
Six years after the triple meltdown at the Fukushima No. 1 nuclear power plant, recent investigations underneath the damaged reactor 2 using cameras and robots came close to identifying melted fuel rods for the first time.
Experts say getting a peek inside the containment vessel of reactor 2 was an accomplishment. But it also highlighted how tough it will be to further pinpoint the exact location of the melted fuel, let alone remove it some time in the future.
The biggest hurdle is the extremely lethal levels of radiation inside the containment vessel that not only prevent humans from getting near but have also crippled robots and other mechanical devices.
Safely removing the melted fuel would be a best-case scenario but the risks and costs should be weighed against the option of leaving the melted fuel in the crippled reactors, some experts said.
“The work to probe inside the containment vessels and remove the fuel debris will be extremely tough because of the high radiation levels,” said Hiroshi Miyano, who heads a panel of the Atomic Energy Society of Japan, which is discussing ways to decommission the Fukushima plant and making recommendations to the government.
The government and Tokyo Electric Power Company Holdings Inc. are trying to find a way to remedy the situation but existing methods and technologies may not be sufficient, Miyano said.
In search of melted fuel
The world’s attention turned to the melted fuel rods in late January when Tepco inserted a 10-meter-plus tube equipped with a camera into the containment vessel of reactor 2 to capture images under the pressure vessel that housed the fuel rods.
The images showed black lumps scattered beneath the pressure vessel.
When the March 11, 2011, Great East Japan Earthquake and monstrous tsunami hit, the plant suffered a blackout and lost its key cooling system, triggering meltdowns in reactors 1, 2 and 3. The melted nuclear fuel rods penetrated the pressure vessels and fell into the containment vessels.
Tepco had put cameras inside the containment vessels several times in the past six years but January’s probe was the first to apparently find melted fuel debris.
“We understand that this is a big milestone. We could finally get to see what it was like underneath the pressure vessel,” said Yuichi Okamura, general manager of Tepco’s nuclear power and plant siting division.
“This is critical information in order to remove the fuel debris.”
Radiation barrier
But Tepco hasn’t confirmed that the black lumps are melted fuel, saying they could be paint or cable wrappings, and further investigation is needed.
Capturing the images may be progress but the robot and camera forays have not provided enough information about how to deal with the melted fuel.
Last month, Tepco sent a remote-controlled, scorpion-shaped robot in to further probe inside the reactor 2 containment vessel. But the robot failed before it reached under the pressure vessel after a tire became stuck.
The robot’s dosimeter measured radiation levels of 210 sieverts per hour — enough to kill humans instantly.
While 210 sieverts per hour indicate the melted fuel was nearby, the radiation crippled the robot’s electronics, including its semiconductors and cameras, indicating that the further use of robots to pinpoint the melted fuel will be difficult, robotics experts said.
There are computer chips “designed to withstand a certain level of radiation, but the level inside the containment vessel is totally different,” said Satoshi Tadokoro, a professor at Tohoku University who is an expert on disasters and rescue robots.
The radiation can damage a robot’s chips that serve as their brains, causing the devices to lose control, said Tadokoro, whose robots have also been used at the Fukushima plant.
“On top of the high level of radiation, the entrance (to the containment vessel) for the robot is very small,” restricting what types of robots can be used to hunt for the melted fuel, he said.
Tepco said the opening it created on the side of the reactor 2 containment vessel is about 11 cm in diameter.
Fuel removal strategy
Tepco is set to conduct internal probes of the reactor 1 containment vessel this month and is preparing similar missions for reactor 3.
The government and utility then plan to adopt a basic fuel removal strategy this summer and fine-tune the plan next year, with the actual fuel removal taking place in or after 2021.
There are essentially three options for the strategy, according to the Tokyo-based International Research Institute for Nuclear Decommissioning (IRID), which is developing technologies for the Fukushima plant decommission.
One option is to flood the containment vessels with water and use a crane above the reactors to hoist up the melted fuel. The second option is to carry out the same process but without water. The third is to install removal equipment through the side of the containment vessel.
There are merits and drawbacks to each option, said Shoji Yamamoto, who heads the team developing technologies to create the fuel removal devices at IRID.
The flooding option can block radiation using water, but if the fuel melts into the water, it could pose a risk of recriticality. The debris may need to be cut into pieces for removal, but this process would enable water to get between multiple pieces, creating the condition for recriticality. For nuclear chain reactions to happen there needs to be a certain distance between nuclear fuel and water.
If there is no water, the recriticality risk is minimal but the massive radiation levels cannot be blocked, Yamamoto said.
Tepco’s Okamura said being able to block radiation with water is a huge plus, but noted the reactor 2 containment vessel had cracks and holes that could let injected coolant water escape.
With the Three Mile Island nuclear accident in the U.S., the flooding option was used to retrieve the melted fuel in the 1980s. But the key difference was that all of the melted fuel stayed inside the pressure vessel, so it was easier to flood the reactor.
Because the melted fuel in reactors 1, 2 and 3 at the Fukushima plant all penetrated the pressure vessels and fell into the containment vessels, extracting it from the top or the side was a tough call, Yamamoto said, noting it was important to know the exact location of the melted fuel.
The distance between the top of the pressure vessel and the bottom of the containment vessel is about 45 meters and some parts inside the pressure vessels will need to be removed if Tepco tries to remove the debris inside the containment vessels from the top.
“If we know that the melted fuel is concentrated in the containment vessels, it will be more efficient to remove it from the side” because the entry point is closer, Yamamoto said.
Whatever option is decided, Yamamoto stressed that maintaining the fuel removal device will be difficult because the radiation will probably cripple it.
“The fuel removal device will be controlled remotely … it will be broken somewhere down the line and the parts will have to be replaced, considering its (ability to withstand) radiation,” he said.
“Given that, maintenance will have to be done remotely, too, and that will be a big challenge.”
To remove or not
Another option altogether is for Tepco to leave the melted fuel where it is.
During a media tour of the Fukushima No. 1 plant last month, Okamura of Tepco said the utility intended to collect the melted fuel because leaving it was “not an appropriate way” to manage nuclear fuel.
Miyano of the Atomic Energy Society of Japan said the debris must be removed because radioactive materials, including nuclear fuel, must be strictly controlled under international rules requiring strict monitoring.
Domestic nuclear power plant operators have to report the amount of nuclear fuel they have to the Nuclear Regulation Authority, which then reports to the International Atomic Energy Agency.
“There is the question of whether the government and Tepco decide not to remove the fuel debris. That would be an international issue,” said Miyano, adding that a consensus from the international community would be needed.
At the same time, Miyano said debate and analysis will be required to decide which choice would be best by looking at various factors, including how much it will cost to pick up all the melted fuel and where to store it.
Footage points to difficulty in removing possible melted fuel at Fukushima plant
The footage released on Jan. 30 by Tokyo Electric Power Co. (TEPCO) showing what could be melted fuel inside the No. 2 reactor at the disaster-stricken Fukushima No. 1 Nuclear Power Plant has highlighted the difficulty of salvaging the object, which is apparently stuck to footholds and other equipment at the facility.
TEPCO took the footage as part of its in-house probe into the No. 2 reactor and found that black and brown sediments — possible melted fuel — are stuck inside the reactor’s containment vessel over an extensive area.
“If what was captured in the footage was melted fuel, that would provide a major step forward toward trying our hand at unprecedented decommissioning work,” said Yoshiyuki Ishizaki, head of TEPCO’s Fukushima Revitalization Headquarters, during a press conference in the city of Fukushima on Jan. 30. “The finding may provide a major clue to future work to retrieve the object,” he added.
At the time of the March 2011 meltdowns at the plant, there were 548 nuclear fuel rods totaling some 164 metric tons inside the No. 2 reactor, but they apparently melted down after the loss of power sources for the core cooling system, with part of the melted fuel penetrating through the pressure vessel before cooling down at the bottom of the containment vessel. The temperature of the reactor core topped 2,000 degrees Celsius at the time of the accident, melting metals including nuclear fuel inside the reactor.
The melted fuel has since come in contact with underground water flowing from the mountain side, generating radioactively contaminated water every day. In order to dismantle the reactor, it is necessary to take out the melted fuel, but high radiation levels inside the reactor had hampered work to locate the melted debris.
On Jan. 30, apart from the footage, TEPCO also released 11 pictures taken inside the No. 2 reactor. The images show the sediments in question stuck to metal grate footholds and water is dripping from the ceiling. Further analysis of those images may provide information on the current status of the disaster and positional clues to decommissioning work.
The in-house probe, however, has only focused on the No. 2 reactor, and there is no prospect of similar probes into the No. 1 and No. 3 reactors starting anytime soon as they were severely damaged by hydrogen explosions following the 2011 meltdowns.
In April 2015, TEPCO introduced a remote-controlled robot into the No. 1 reactor by way of a through hole in its containment vessel, but the device failed to locate melted fuel inside due to high radiation levels. While the utility is planning to send a different type of robot into the No. 1 reactor this coming spring, it would be difficult to carry out a survey similar to that conducted at the No. 2 reactor, as radiation levels are high around the through hole in the No. 1 reactor’s containment vessel, from which a device could access to right below the No. 1 reactor.
The No. 3 reactor, meanwhile, holds roughly 6.5-meter-deep contaminated water inside its containment vessel, a far larger volume than that accumulated at the No. 1 and No. 2 reactors. TEPCO has thus been developing a robot that can wade through water.
http://mainichi.jp/english/articles/20170131/p2a/00m/0na/007000c
Plans to remove nuclear fuel at Fukushima N° 3 reactor delayed again
A member of the media, wearing a protective suit and a mask, looks at the No. 3 reactor building at Tokyo Electric Power Co’s (TEPCO) tsunami-crippled Fukushima Daiichi nuclear power plant in Okuma town, Fukushima prefecture, Japan February 10, 2016.
A plan to remove spent nuclear fuel from Tokyo Electric Power Co Holdings Inc’s Fukushima Daiichi nuclear plant hit by the March 2011 tsunami has been postponed again due to delays in preparation, the Nikkei business daily reported on Thursday.
Work is now set to begin in fiscal 2018 at the earliest, the Nikkei said.
Removal of the spent fuel from the No. 3 reactor was originally scheduled in the first half of fiscal 2015, and later revised to fiscal 2017 due to high levels of radioactivity around the facilities, the Japanese business daily reported.
The timeline has been changed again as it was taking longer than expected to decontaminate buildings and clean up debris, the news agency reported.
The report comes a few months after the Japanese government said in October the cost of cleaning up the Fukushima plant may rise to several billion dollars a year, adding that it would look into a possible separation of the nuclear business from the utility.
http://uk.reuters.com/article/uk-japan-fukushima-idUKKBN1592WI
Fuel Removal from Fukushima Reactor 3 Likely to Be Put Off Again
Tokyo, Nov. 18 (Jiji Press)–Tokyo Electric Power Co. Holdings Inc. <9501> is expected to face a further delay in the start of work to remove fuel from the storage pool at the No. 3 reactor of its disaster-stricken Fukushima No. 1 nuclear power station, it was learned Friday.
It now appears difficult to begin the work in January 2018, as currently targeted by the company, the sources said. The expected postponement is due to a delay in preparations necessary for the removal work.
All six reactors at the power station in Fukushima Prefecture, northeastern Japan, are set to be decommissioned, after the plant was knocked out by the March 2011 earthquake and tsunami. Three of the six reactors suffered core meltdowns in the accident.
The fuel removal from the No. 3 reactor pool was initially planned to begin during April-September 2015.
The No. 3 reactor building was heavily damaged by a hydrogen explosion soon after the March 11 disaster. As part of the preparations, TEPCO plans to install a cover and relevant equipment at the reactor.
http://jen.jiji.com/jc/eng?g=eco&k=2016111800715
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