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TEPCO to Remove Contaminated Pipes at Fukushima Daiichi Nuclear Power Plant by “First Half of FY2022” Due to Continuing Troubles

A cutting device lifted by a large crane grabs a 30-centimeter-diameter pipe at the Fukushima Daiichi Nuclear Power Plant on March 2, 2022 (photo by Takeshi Yamakawa)

April 18, 2022
On April 18, at a meeting of the Nuclear Regulation Authority to review the status of the accident at the Fukushima Daiichi Nuclear Power Plant, TEPCO announced that it had changed its target date for the completion of work to “the first half of FY2022 (April to September)” regarding the removal of pipes between Units 1 and 2 that were contaminated with high concentrations of radioactive materials. Previously, the target was “within FY 2009. The scope of the removal work includes the areas that interfere with the installation of rainwater inflow countermeasures in the waste treatment buildings of Units 1 and 2 and the installation of a large cover in Unit 1.
 The removal work began on February 24, but has not progressed at all due to a series of problems with the cutting equipment. The timing for the resumption of work is not clear, as investigations are still underway to determine whether the cutting equipment and method used to lift the pipes up by a large crane are appropriate.
 The pipes to be removed were used in the venting process immediately after the accident to release contaminated air inside the reactor to prevent the containment vessel from rupturing. The pipes are 30 cm in diameter and measure 65 meters on the Unit 1 side and 70 meters on the Unit 2 side. The current plan is to cut the piping into 26 sections and remove them. The surface dose at the connection with the exhaust stack is 4 sievert per hour, which is high enough to kill a person if he or she stays there for several hours. For this reason, all work will be carried out remotely. (Shinichi Ogawa)
https://www.tokyo-np.co.jp/article/172472?rct=national&fbclid=IwAR1DYTcIpK–IpNqQfheOVBWKG8-G1Eonb274DLuS8FOMWxZ9ciYQLdmaiM

April 23, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

Latest look inside Fukushima’s ruins shows mounds of melted nuclear fuel

About 900 tons of melted nuclear fuel remain inside the plant’s three damaged reactors.

February 16, 2022

A remote-controlled robot has captured images of melted nuclear fuel inside Japan’s wrecked Fukushima nuclear plant.

A massive earthquake and tsunami in 2011 damaged cooling systems at the power plant, causing the meltdown of three reactor cores.

Most of their highly radioactive fuel fell to the bottom of their containment vessels, making its removal extremely difficult.

A previous attempt to send a small robot with cameras into the Unit 1 reactor failed, but images captured this week by a ROV-A robot show broken structures, pipes and mounds of what appears to be melted fuel.

Other debris was also submerged in cooling water, according to Tokyo Electric Power Company Holdings (TEPCO), the plant operator.

About 900 tonnes of melted nuclear fuel remain inside the plant’s three damaged reactors, including about 280 tons in Unit 1.

Its removal is a daunting task that officials say will take 30-40 years. Critics say that’s overly optimistic.

The robot, carrying several tiny cameras, obtained the internal images of the reactor’s primary containment vessel while on a mission to establish a path for subsequent probes, TEPCO said.

TEPCO spokesperson Kenichi Takahara said the piles of debris rose from the bottom of the container, including some inside the pedestal — a structure directly beneath the core — suggesting the mounds were melted fuel that fell in the area.

Takahara said further probes will be needed to confirm the objects in the images.

At one location, the robot measured a radiation level of 2 sievert, which is fatal for humans, Takahara said. The annual exposure limit for plant workers is set at 50 millisievert.

Images from a remote-controlled submersible robot show damaged areas inside the Fukushima nuclear power plant damaged in the 2011 earthquake and tsunami in Fukushima, Japan.

The robot probe of the Unit 1 reactor began on Tuesday and was the first since 2017 when an earlier robot failed to obtain any images of melted fuel because of the extremely high radiation and interior structural damage.

The fuel at Unit 1 is submerged in highly radioactive water as deep as 2 meters (6.5 feet).

TEPCO said it will conduct additional probes after analyzing the data and images collected by the first robot.

The investigation at Unit 1 aims to measure the melted fuel mounds, map them in three dimensions, analyze isotopes and their radioactivity, and collect samples, TEPCO officials said.

Those are key to developing equipment and a strategy for the safe and efficient removal of the melted fuel, allowing the reactor’s eventual decommissioning.

Details of how the highly radioactive material can be safely removed, stored and disposed of at the end of the cleanup have not been decided.

TEPCO hopes to use a robotic arm later this year to remove an initial scoop of melted fuel from Unit 2, where internal robotic probes have made the most progress.

February 20, 2022 Posted by | Fuk 2022 | , , | Leave a comment

Robot photos appear to show melted fuel at Fukushima reactor

MARI YAMAGUCHI – February 10, 2022

TOKYO (AP) — A remote-controlled robot has captured images of what appears to be mounds of nuclear fuel that melted and fell to the bottom of the most damaged reactor at Japan’s wrecked Fukushima nuclear plant, officials said Thursday.

A massive earthquake and tsunami in 2011 damaged cooling systems at the power plant, causing the meltdown of three reactor cores. Most of their highly radioactive fuel fell to the bottom of their containment vessels, making its removal extremely difficult.

A previous attempt to send a small robot with cameras into the Unit 1 reactor failed, but images captured this week by a ROV-A robot show broken structures, pipes and mounds of what appears to be melted fuel and other debris submerged in cooling water, plant operator Tokyo Electric Power Company Holdings said Thursday.

About 900 tons of melted nuclear fuel remain inside the plant’s three damaged reactors, including about 280 tons in Unit 1. Its removal is a daunting task that officials say will take 30-40 years. Critics say that’s overly optimistic.

The robot, carrying several tiny cameras, obtained the internal images of the reactor’s primary containment vessel while on a mission to establish a path for subsequent probes, TEPCO said.

TEPCO spokesperson Kenichi Takahara said the piles of debris rose from the bottom of the container, including some inside the pedestal — a structure directly beneath the core — suggesting the mounds were melted fuel that fell in the area.

Takahara said further probes will be needed to confirm the objects in the images.

At one location, the robot measured a radiation level of 2 sievert, which is fatal for humans, Takahara said. The annual exposure limit for plant workers is set at 50 millisievert.

The robot probe of the Unit 1 reactor began Tuesday and was the first since 2017, when an earlier robot failed to obtain any images of melted fuel because of the extremely high radiation and interior structural damage.

The fuel at Unit 1 is submerged in highly radioactive water as deep as 2 meters (6.5 feet).

TEPCO said it will conduct additional probes after analyzing the data and images collected by the first robot.

Five other robots, co-developed by Hitachi-GE Nuclear Energy and the International Research Institute for Nuclear Decommissioning, a government-funded consortium, will be used in the investigation over the next several months.

The investigation at Unit 1 aims to measure the melted fuel mounds, map them in three dimensions, analyze isotopes and their radioactivity, and collect samples, TEPCO officials said.

Those are key to developing equipment and a strategy for the safe and efficient removal of the melted fuel, allowing the reactor’s eventual decommissioning.

Details of how the highly radioactive material can be safely removed, stored and disposed of at the end of the cleanup have not been decided.

TEPCO hopes to use a robotic arm later this year to remove an initial scoop of melted fuel from Unit 2, where internal robotic probes have made the most progress.

https://www.yahoo.com/now/robot-photos-appear-show-melted-134212334.html

February 13, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

Delayed robot probe of Fukushima reactor begins

Feb. 8, 2022

The operator of the damaged Fukushima Daiichi nuclear power plant has begun its delayed robot probe of the inside of the facility’s No.1 reactor.

Tokyo Electric Power Company, or TEPCO, had planned to start the survey of the reactor’s containment vessel on January 12, but postponed it due to mechanical trouble.

Engineers noticed during preparations that data from radiation-measuring equipment installed in a robot was not shown correctly.

The engineers later found out that electromagnetic waves emitted from the robot’s device for extending and winding up cables had affected its radiometers. They solved the problem, and confirmed that the data was then shown accurately.

TEPCO started the survey on Tuesday morning. Officials of the utility say they initially planned to end the probe by August, but that the schedule will be moved back due to the delay.

The probe is part of efforts to remove molten fuel debris from inside the reactor.

https://www3.nhk.or.jp/nhkworld/en/news/20220208_26/

February 10, 2022 Posted by | Fuk 2022 | , , | Leave a comment

Fukushima Operators Send Robot Into Worst-Hit Melted Reactor

The damaged Unit 1 reactor, back, and the exhaust stack shared with the Unit 1 and 2 reactors at the Fukushima Daiichi nuclear power plant stand along the coast of Okuma town, Fukushima prefecture, northeastern Japan, Saturday, Feb. 27, 2021. A remote-controlled robot was used on Tuesday, Feb. 8, 2022, to probe the hardest-hit nuclear reactor at Japan’s wrecked Fukushima plant, as officials push forward with recovery and clean-up operations that have been mired in delays and controversy. (AP Photo/Hiro Komae, File)

Feb. 8, 2022

By MARI YAMAGUCHI, Associated Press

TOKYO (AP) — A remote-controlled robot on Tuesday was used to probe the hardest-hit nuclear reactor at Japan’s wrecked Fukushima plant, as officials push forward with clean-up operations that have been mired in delays and controversy.

An earthquake and tsunami in 2011 unleashed a disastrous meltdown at Fukushima Daiichi’s three reactors that partly sunk their radioactive cores into the plant’s concrete foundations, making removal extremely difficult.

The plant’s operator, Tokyo Electric Power Company Holdings, said the submersible robot was sent into Unit 1’s primary containment vessel to install a guiding path for five subsequent robots, which will attempt to asses and take samples of the melted fuel that emits fatally high radiation.

Tuesday’s probe followed five years after the operators sent another robot into the same and badly-damaged reactor, but failed to get any images of the melted fuel.

The robot-led work, which was postponed from mid-January due to mechanical glitches, is expected to last for a few days before full-fledged probes begin.

Earlier probes showed that the fuel at Unit 1 is submerged by highly radioactive water as deep as 2 meters (6.5 feet).

Five other robots, co-developed by Hitachi-GE Nuclear Energy and the International Research Institute for Nuclear Decommissioning, a government-funded consortium, will be separately sent in for the investigation over the next several months.

The probe at Unit 1 aims to measure the melted fuel mounds, map them in three dimensions, analyze isotopes and their radioactivity, and collect samples, Tokyo Electric officials said.

Those are key to developing equipment and a strategy for a safe and efficient melted fuel removal.

About 900 tons of melted nuclear fuel remain inside the plant’s three reactors, including about 280 tons in Unit 1, and its removal is a daunting task that officials say will take 30-40 years. Critics say that’s overly optimistic.

Remote-controlled robots with cameras have provided only a limited view of the melted fuel in areas too dangerous for humans to reach. In 2017, super-high levels of radiation and structural damage hampered investigating Unit 1.

Details of how the highly radioactive material can be safely removed, stored and disposed at the end of the cleanup have not been decided.

Tokyo Electric hopes to use a robotic arm to remove a first scoop of melted fuel later this year from Unit 2, where internal robotic probes have made the most progress.

Fisherman and residents of Fukushima’s outlying areas have protested the operator’s plans to discharge into the nearby sea radioactive waters from the reactors, after treating and diluting them to safely releasable levels.

https://www.usnews.com/news/news/articles/2022-02-08/fukushima-operators-send-robot-into-worst-hit-melted-reactor

February 10, 2022 Posted by | Fuk 2022 | , , | Leave a comment

“We don’t know if it’s debris.” Bumpy deposits at the bottom of the reactor.

February 9, 2022
 On February 9, Tokyo Electric Power Company (TEPCO) released a video of the bottom of the containment vessel of the Unit 1 reactor at the Fukushima Daiichi Nuclear Power Plant (Okuma and Futaba towns, Fukushima Prefecture) taken by an underwater robot during an internal investigation. From the images, it was confirmed that orangeish bumpy deposits were spreading and adhering to the structure inside the vessel. It is possible that it is nuclear fuel (debris) that melted down during the accident. We don’t know if it is debris at this stage,” said Kenichi Takahara, a spokesman, at a press conference.

A video of the bottom of the containment vessel of the Unit 1 reactor shows a bumpy deposit spreading from the bottom center to the right side of the vessel at TEPCO’s Fukushima Daiichi Nuclear Power Plant (Courtesy of TEPCO)

According to TEPCO, it is unclear how high the confirmed deposit is; a survey in March 2017 confirmed a deposit of 90 centimeters high near this location. According to TEPCO, the height of the debris is unknown.

A part of the piping that was cut off for the introduction of the robots has sunk to the bottom of the containment vessel of the Unit 1 reactor (Courtesy of TEPCO)

By around 1:50 p.m. on the 9th, the underwater robot that was deployed on the afternoon of the 8th had moved through the water inside the containment vessel and attached four guide rings with a diameter of 30 centimeters at intervals to the structure inside the vessel. The purpose of these rings was to prevent cables from getting tangled in the structure when the robot, which will be used in the future, moves around, and we were finally ready for a full-scale investigation.

In the containment vessel of the Unit 1 reactor, an underwater robot moves through the vessel while attaching rings to the structure (TEPCO)

Oil-like suspended matter was observed on the water surface inside the containment vessel of the Unit 1 reactor. The yellow glow in the center is a pipe illuminated by a light (TEPCO)

 The radiation level in the water was 1 to 2 sievert per hour. The radiation level in the water was 1 to 2 sievert per hour. The exposure limit for workers at the nuclear power plant is 50 millisieverts per year, and even if one were to enter the water, it would take only 1 to 3 minutes to reach the exposure limit, so people are not allowed to go near the water.

A worker opens a valve leading to the containment vessel of the Unit 1 reactor to insert a robot (Courtesy of TEPCO)

Workers insert an underwater robot outside the containment vessel of the Unit 1 reactor (Courtesy of TEPCO)

 Of the three reactors that suffered core meltdowns in the March 2011 accident, video footage shows deposits of what appears to be debris in Units 2 and 3, but no debris was found in Unit 1 during the 2005 survey.
 Removing the debris is the most difficult task, and it is estimated that a total of 880 tons has melted down in Units 1-3. TEPCO is aiming to collect a few grams of debris from the Unit 2 reactor by the end of this year. (Shinichi Ogawa, Kenta Onozawa)
https://www.tokyo-np.co.jp/article/159265?fbclid=IwAR08nc1U0duYKVLHyBgjGnoRnhVI944BMtWrN-6F8HNVGUlKXTpkkFAItm4

February 10, 2022 Posted by | Fuk 2022 | , , | Leave a comment

Fukushima Unit 1: First internal investigation in 5 years

Underwater robot captures images of reactor containment vessel

2022/02/08
The Tokyo Electric Power Company (TEPCO) began an internal investigation of the containment vessel at the Unit 1 reactor of the Fukushima Daiichi Nuclear Power Plant on February 8. An underwater robot was used to collect information on the sediment accumulating at the bottom of the vessel and the molten nuclear fuel (debris) underneath. This is the first time in about five years since March 2017.

 According to the images taken by the camera mounted on the robot, the bottom of the containment vessel was bumpy, as if something had accumulated there. A TEPCO official said, “We don’t know yet whether it is a deposit or not, and we will proceed with the investigation.

 The investigation was scheduled to start on January 12, but was postponed due to problems during the preparation work. TEPCO is now reconsidering the process, which was set to last until August.
https://www.minpo.jp/globalnews/moredetail/2022020801001260?fbclid=IwAR0YiLHqKhJNuprOuxehkLnPzsAYBMFHgQ_0hcLHnWwpllUn9CFD2zSjR10

February 9, 2022 Posted by | Fuk 2022 | , , | Leave a comment

Robotic failure: “We don’t know the cause, and the outlook is unclear…” High barrier to internal investigation of high radiation dose at Fukushima Daiichi Nuclear Power Plant Unit 1

January 15, 2022

Due to a robot malfunction, an internal inspection of the Unit 1 reactor at TEPCO’s Fukushima Daiichi Nuclear Power Plant (located in the towns of Okuma and Futaba in Fukushima Prefecture) has not been able to begin. The radiation level inside the containment vessel, where melted nuclear fuel (debris) remains, is too high for people to approach. The work, which requires remote control, has had a series of problems. As the eleventh anniversary of the accident approaches, a high wall continues to block the way. (Kenta Onozawa)


Advance preparations were too lax.
 We didn’t know the cause of the accident. We don’t know the cause, we don’t know the prospects for countermeasures, and we haven’t decided when to resume the investigation.
 At a press conference on March 13, a TEPCO spokesman gave a vague answer. The internal investigation of the Unit 1 reactor, which was delayed for more than two years from the original plan, was supposed to start on the 12th, but it stalled right from the start.
 Of the three reactors that suffered meltdowns, Unit 1 is the only one where no debris has been found. The survey this time has been planned with a lot of effort to make up for the delay, including the use of six different types of robots with multiple functions, and the survey will take about seven months.
 The first underwater robot (25 centimeters in diameter and 111 centimeters in length) will be used to create a survey route. A 30-centimeter-diameter guide ring will be attached to the robot so that subsequent robots can pass through it to prevent cables from getting tangled, which the spokesperson stresses is essential for the survey.

Status of Containment Vessel Survey at Fukushima Daiichi Nuclear Power Plant


However, the preparations in advance were lax. The preliminary tests were limited to confirming the operation of each piece of equipment, and the team was unable to immediately respond to problems with the dosimeters that occurred when they were operated simultaneously.


In the past, there have been cases of “leaving things behind.
 It is expected to take some time to identify the cause of the problem. If similar problems occur with other robots, plans to take images of the inside of the containment vessel, grasp its three-dimensional structure, and collect sand-like deposits in the water will not be able to proceed and may be abandoned.
 We know from previous studies that complex devices are less effective, such as the underwater robot that photographed debris deposits inside the containment vessel of Unit 3 in 2017. The underwater robot that photographed the debris in the containment vessel of the Unit 3 reactor in 2017 was about a quarter of the length and had a simpler structure. It also focused on photographing as its main purpose.
 In the 2006 survey that succeeded in photographing the debris in the Unit 2 reactor, a worker inserted a pipe (13 meters long) with a camera attached to the end, rather than a robot. In the previous year, a camera-equipped pipe was inserted. In the previous year, a camera-equipped robot called a “scorpion” was deployed, but it climbed up on the sediment and could not be retrieved, remaining in the reactor.


Although “human power” can be used to deal with the problem outdoors…
 Remote-controlled operations are always fraught with difficulties, even outside the building where the reactor is located.

TEPCO’s Fukushima Daiichi Nuclear Power Plant, where work to bring the accident under control is underway. From left: Unit 1 and Unit 2 in Okuma Town, Fukushima Prefecture.


 The exhaust stack near the Unit 1 and 2 buildings, which was in danger of collapsing due to the earthquake and was highly contaminated, was cut down to about 60 meters, half the height of the original stack (1 In one case, the saw blade of a cutting device lifted by a large crane got stuck in the cylinders and could not be moved. At that time, a worker climbed up to the cutting device installed at the top of the 110-meter-high cylinder with a crane and cut it with a power tool.
 In late January, they plan to cut the contaminated pipes leading to this exhaust stack. The project was originally supposed to start four months ago, but there was a problem with the remote-controlled cutting device and the crane broke down, delaying the plan.
 Debris collection is planned for Unit 2 by the end of the year. If a problem occurs in the reactor, we cannot rely on human power.
https://www.tokyo-np.co.jp/article/154269?fbclid=IwAR2E55S3DYLr7KiroYjxza6u_MX67pvMdrWioFykfOwgoxBdOlqhOraX9WI

Translated with http://www.DeepL.com/Translator (free version)

January 15, 2022 Posted by | Fuk 2022 | , , | Leave a comment

TEPCO to begin robot probe of Fukushima reactor

Jan. 6, 2022

The operator of the crippled Fukushima Daiichi Nuclear Power Station says it will launch a probe of the inside of the No.1 reactor on Wednesday using robots. The firm is seeking to clear debris from the reactor interior as part of the decommissioning process.

Tokyo Electric Power Company, or TEPCO, says the probe will involve six types of robots, each with a different function.

It says the survey will continue for more than six months. It will use ultrasonic devices to locate and measure the thickness of debris believed to be submerged under water inside the reactor containment vessel.

The utility says it also hopes to collect small samples of the debris.

TEPCO says it will use a robot to install a cover on a path for the survey machines to move smoothly under water.

The No.1, 2 and 3 reactors of the plant suffered meltdowns in the massive earthquake and tsunami of 2011.

TEPCO confirmed the existence of what is believed to be solid fuel debris inside the No.2 and 3 reactors, but not inside the No.1 reactor. The debris consists of molten nuclear fuel and metal parts.

Fukushima Daiichi Decontamination & Decommissioning Engineering Company, which was established by TEPCO, said on Thursday it will use the robots to gather information before considering how to remove the debris.

https://www3.nhk.or.jp/nhkworld/en/news/20220107_02/

January 8, 2022 Posted by | Fuk 2022 | , , | Leave a comment

Upcoming Inspection of Fukushima Unit 1

November 25, 2021

TEPCO announced that the next phase of containment inspections inside unit 1 will finally take place in early 2022. This next phase of inspections had been delayed due to technical challenges, concerns of radioactive dust releases, then due to the pandemic.


Some of the explanatory materials provide new insight into the true situation inside unit 1. It has been speculated since 2011 that melted fuel (aka corium) flowed out of the pedestal of unit 1, across the containment floor, and burned through the thin connection edge of the containment structure. Diagrams included in this most recent report show that the entities tasked with decommissioning the damaged reactors think so too. Diagrams originally from NDF, the decommissioning authority, and IRID, the main agency tasked with research, show the same.


The graphic below shows a significant pile of melted fuel in the pedestal and along the outer edge of the containment structure. The right side graphic shows melted fuel a significant way up to the lower edge of the downcomer tubes that route into the torus tube. Evidence of fuel debris inside the torus tube was found in earlier inspections along with our early findings that appeared to show fuel debris under the water in the torus room outside of containment.

This side view of the same area shows what IRID and TEPCO assume to be the situation inside unit 1’s containment as they prepare for the upcoming inspections.The red color is solidified previously melted fuel, The brown layer is the sediment layer and the blue layer is standing water inside containment. The sediment layer on the right side where inspections have already taken place is significantly lower than the sediment bed directly adjacent to the assumed location of the fuel debris. The depth difference appears to be 3 times as much adjacent to the melted fuel locations.

The debris bed on the shallow right side was roughly 4-10 inches deep based on TEPCO estimates in 2017. If the left side adjacent to the solidified fuel is 3 times the depth, it would be 12-30 inches in depth. What exactly this debris bed is and how it developed had caused head-scratching for years. A TEPCO report in 2017 showed it contained stainless steel, materials related to shielding, cabling, and some low levels of reactor-based radioactive isotopes. If this material contained additional substances or not was a bit ambiguous. There had been some initial assumptions this was pulverized concrete. There may have been some involvement of the concrete structures into this debris pile through mechanical destruction or molten corium concrete interaction, but TEPCO provides insufficient data to confirm or rule this out.


Another 2017 report gave some rough estimates of the depth of the known parts of the debris bed. The known parts from an earlier set of inspections would be the general area marked by the A in the above graphic. This area is roughly 4 – 10 inches in depth. The left side adjacent to the solidified fuel would then be about 12 – 30 inches in depth. The deposits closer to the pedestal opening were close to 1 meter deep on a 2017 inspection. TEPCO could not determine if there was any solidified fuel beneath. They assumed the debris bed was providing extensive shielding that would prevent the detection of any layer of solidified fuel. This debris bed appears to reside 1/3 of the way up the downcomer cover. It is likely some amount of it has entered the torus tube and potentially the torus room.


Upcoming Inspections:
The upcoming inspections include a total of 6 ROV units. The remote operational vehicles are not true robots as each one has a control tether. The biggest concern with these units is having one become stranded, preventing the introduction of future ROV units to continue inspections. Each ROV unit has an assigned task. Due to internal equipment inside containment, a series of rings will be placed by the first ROV to help guide the ROV units and prevent entanglement.

ROV-A

ROV-A will attempt to traverse the south direction to the pedestal doorway.

ROV-A2 will attempt to enter the pedestal to capture imagery of the conditions and potential fuel location.

ROV units B to E each have similar tasks tied to characterizing the fuel debris and sediments.
Each ROV has about an 80-hour high radiation tolerance. They will be introduced by the level of risk with ROV-A2 going into the pedestal last due to the high risk. Preparation work begins in January. The entire series of inspections are currently scheduled to take 10 months to complete.

December 10, 2021 Posted by | Fukushima 2021 | , , | Leave a comment

Robots to probe Fukushima No.1 reactor from Jan.

Thursday, Nov. 25, 2021

NHK has learned that the operator of the Fukushima Daiichi nuclear plant plans to start a delayed robot survey of a damaged reactor from mid-January.

Officials of Tokyo Electric Power Company say preparations are well under way to send submersible robots inside the containment vessel of the No.1 reactor.

The probe is part of efforts to remove molten fuel debris from the reactor that suffered a meltdown accident due to the 2011 earthquake and tsunami.

The utility originally planned to start the robot survey of the reactor in 2019.

It has been postponed because preparations, such as making a hole in the door of the vessel for the robots to go through, have taken time.

The officials say they are now installing equipment to remotely control the robots, and expect to carry out a survey for more than six months from mid-January.

They plan to use a total of six robots with different functions to find and examine nuclear debris, or deposits of a mixture of molten fuel and reactor parts, inside the containment vessel.

The robots will use ultrasonic devices to locate and measure how much debris there is, and how thick the deposit is. They are also expected to collect a small amount of samples.

Previous surveys at the plant confirmed the presence of deposits believed to be fuel debris in the No.2 and No.3 reactors, which also suffered meltdowns, but not in the No.1 reactor.

https://www3.nhk.or.jp/nhkworld/en/news/20211125_22/

November 26, 2021 Posted by | Fukushima 2021 | , , | Leave a comment

Protective sheet positioned at damaged reactor

20200612_02_847900_L

June 12, 2020

The operator of the crippled Fukushima Daiichi nuclear plant has released footage showing part of the time-consuming steps needed to remove nuclear fuel from a pool at its No.1 reactor.

In the video, workers used remote-controlled tools to place a wide sheet over the surface of the pool. The radiation level there remains high.

Tokyo Electric Power Company has been engaged in removing debris from the upper part of the reactor building where the pool is located. The debris was caused by an explosion during the 2011 nuclear accident.

The sheet is meant to protect the pool and 392 nuclear fuel assemblies still inside from further damage that could result from the possible falling of debris or large machinery.

The six-by-eleven meter sheet is inflatable to a thickness of 50 centimeters. It will be filled with cement to increase its strength.

The operator plans to begin clearing the debris from around the pool by the end of the month, as soon as the sheet’s cement has solidified.

The operator plans to start removing the fuel from the pool of the No.1 reactor in fiscal 2027. Similar work at the No.2 reactor will start in fiscal 2024. Fuel removal from the pool at the No.3 reactor will be completed by fiscal 2020. The removal work is finished at the No.4 reactor.

https://www3.nhk.or.jp/nhkworld/en/news/20200612_02/?fbclid=IwAR0aZXia773hoajuSLTJZO3GyZTSggWHrQ6yXEnSqzT7p9K8zkg7YGiQ33s

 

June 22, 2020 Posted by | Fukushima 2020 | , , | Leave a comment

TEPCO begins studying dislodged reactor cover

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Translation by Rachel Clark
July 17, 2019
At TEPCO’s Fukushima Daiichi Nuclear Power Station Unit 1, the top lid of the containment vessel covering the reactor has been shifted (or out of proper position). Because of this, the radiation dose in the building became high, which has been an obstacle to decommissioning work, TEPCO has started to conduct its investigation on the 17th to check the situation of the shifted upper lid and contamination using a robot.
 
The first unit of Fukushima Daiichi Nuclear Power Plant was affected by the hydrogen explosion at the time of the accident, and the upper lid of the three layers of the containment vessel covering the nuclear reactor was shifted from its proper position.
Because of this, radiation dose around this reactor goes up as high as 2.23 Sv/h.
For this reason, it is necessary to lower the radiation dose either by taking out the fuel left in the spent fuel pool in the Unit 1 building, or by correcting the position of the lid that weighs about 60 tons, or by installing a new cover, etc. On the 17th, TEPCO started to investigate the situation by a remote-controlled robot for more details.
In their plan, first they want to put the robot in the gap between the upper and middle lids among the three layers of lids, then to lower the camera and confirm the condition of the lowest tier, and to wipe the surface of the lid measured with a three-dimensional scanner, in order to collect radioactive materials.
On the 17th, TEPCO started the investigation from 3:00 pm. What they actually doing now is to take photos in order to confirm the view of a robot’s camera.
The investigation will be continued through early next month, of which the results will help TEPCO examine the necessity of decontamination as well as of moving the lids and shielding radiation.
TEPCO begins studying dislodged reactor cover
July 18, 2019
The operator of the damaged Fukushima Daiichi nuclear power plant has begun a robot survey of a dislodged cover of the facility’s No.1 reactor containment vessel. High radiation leaking from the area is hindering Tokyo Electric Power Company, or TEPCO, from carrying out decommissioning work.
The roughly 500-ton, three-layer cover was dislodged by a hydrogen explosion after the March 2011 earthquake and tsunami.
Around the cover, radiation levels as high as 2.23 sieverts per hour have been detected.
TEPCO plans to remove 392 nuclear fuel assemblies from a cooling pool next to the reactor container.
But workers must either put the cover back in place or install a shield to lower radiation levels before starting the work.
The firm began examining the dislodged cover on Wednesday.
Engineers are sending robots between the cover’s top and middle sections to conduct 3D scanning and collect samples of radioactive material from its surface.
TEPCO is to continue the survey through early next month and consider what needs to be done.

July 27, 2019 Posted by | fukushima 2019 | , | Leave a comment