Inspection of Fukushima Daiichi Unit 3 Spent Fuel Pool’s Damage
TEPCO reported in late November on some ongoing work to inspect the remaining fuel and equipment in the Unit 3 spent fuel pool. Work took place between July and October of 2021. Part of this work included equipment in the pool classified as high radiation. This included used control rods and other high radiation equipment such as used filter canisters.
The inspection found a damaged control rod lying across a fuel rack, two damaged control rods hung in the wall rack, and damage to the rack itself. Two “dummy” fuel assemblies have damaged lifting handles and six lifting tabs on the fuel racks were damaged. Sandy debris and rust were found at the bottom of the pool, causing difficulty in examining the used filters stored in the pool.
TEPCO wasn’t able to obtain clear radiation readings due to the depth of the debris in the bottom of the pool. The highest location they were able to take a reading was near the control rod found lying across the fuel rack. That reading was 265 mSv/h. TEPCO planned to begin removing debris from the fuel rack in November of 2021. Work to remove the control rods and high-dose equipment would begin in mid-2022.
A translated version of the TEPCO report can be found here:
https://www.dropbox.com/s/z3wn2ie2y2davn3/spent_fuel_d211125_08-j_u3_translated.pdf?dl=0
The original report in Japanese can be found here:
https://www.dropbox.com/s/s1kgdpexcbxeclm/spent_fuel_d211125_08-j.pdf?dl=0
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).
Fukushima Daiichi Nuclear Power Plant Unit 3 Finished Removing Deformed Nuclear Fuel
A supposedly excellent news. However to the risk of sounding the suspicious type, the one thing that I have learned covering for the past 10 years the ongoing nuclear disaster of Fukushima daiichi, is that when Tepco releases some good news it is usually to cover up a bad news, a bad happening behind the good news. Because for Tepco and the nuclear village, lying and secrecy are their second nature. They never inform us on time of what is really up. And just after the last severe earthquake that occured, we have all the reasons to believe that they are not telling us the real facts as usual.
February 20, 2021
The Tokyo Electric Power Company (TEPCO) has announced that it has finished using a special device to remove nuclear fuel that was partially deformed in the accident and could not be pulled out of the spent fuel pool.
Since last year, the Unit 3 reactor at the Fukushima Daiichi Nuclear Power Plant has been in the process of transferring 566 nuclear fuels in the spent fuel pool to a safe facility on the plant grounds.
Of these, four nuclear fuels have a handle on the top of the fuel that was deformed by the debris that fell into the pool during the accident, making it impossible to lift the fuel with normal equipment.
Therefore, TEPCO, in cooperation with a manufacturer, developed a device with an ingenious shape so that even if the handle is deformed, it can be grabbed and pulled up, and announced that they started removing four fuel cells this month and finished removing them this week.
When the fuel was pulled up, it was slightly tilted and lifted up, unlike normal, healthy fuel, but there were no safety problems and the work was completed.
With this, the work to remove the nuclear fuel from the spent fuel pool of the Unit 3 reactor has passed a milestone, and the number of remaining nuclear fuel is 22, and TEPCO plans to finish removing all the fuel by next month.
Japan’s nuclear regulator maintains view on Fukushima Daiichi’s No.3 reactor blasts
November 13, 2020
Japan’s nuclear regulator has maintained its view that multiple blasts occurred at the Fukushima Daiichi nuclear power plant’s No.3 reactor following the earthquake and tsunami in 2011.
The plant suffered meltdowns from the accident. Three reactor buildings were severely damaged by hydrogen explosions.
On Thursday, the Nuclear Regulation Authority along with experts analyzed images taken at the No.3 reactor.
Officials say the state of buckled beams on the third floor indicates an instantaneous wind pressure of up to 5 atmospheres. The officials say such force can damage concrete structures and collapse wooden buildings.
They also studied the only footage of the No.3 reactor in the explosion, which was captured by a TV station in Fukushima Prefecture.
The officials say an analysis of image processing shows the first blast damaged the fourth floor. They say an ensuing fire on the uppermost fifth floor caused the remaining hydrogen to explode, which caused black smoke to emerge.
The regulator resumed its probe into the cause of the accident last year. It plans to draw up a report as early as next month.
Video release of Fukushima Daiichi Unit 3 – High radiation
Images of the interior of the damaged reactor 3 building taken by the man on December 12th 2019, have just been made public. Up to 30 millisievert / h on the 3rd floor.
Video released of Fukushima No.3 reactor interior
Fukushima Unit 3 Spent Fuel Damage Identified
Nuclear fuel transfer resumes at Fukushima Daiichi
New Discovery At Fukushima Unit 3 Provides Clues To Meltdown Severity, Environmental Releases
May 3, 2019
TEPCO recently published a video of the work to remove spent fuel from the unit 3 fuel pool. In this video was an unexpected finding with serious implications.
In the video of the fuel assembly removal from a fuel rack inside the spent fuel pool, was a tell tale sign of something significant. Prior to the effort to remove fuel from the pool, the pool underwent significant cleaning work. This included removing most of the debris that fell into the pool along with use of a vacuum to remove small pieces of broken concrete and dust.
What remains adhered to the side of the fuel rack appears to be the same thick white substances found inside the reactor containment of unit 3 and in the pedestal below the reactor vessel. These substances also have the same appearance as those inside containment. They are stuck to both vertical and horizontal surfaces as if they splattered then stuck to where they landed. What these may be and how they managed to end up on the fuel racks is explained further in this report.
Read more:
Simply Info
New Discovery At Fukushima Unit 3 Provides Clues To Meltdown Severity, Environmental Releases
Submersible robot ‘little sunfish’ to inspect the damaged primary containment vessel (PCV) of Fukushima Daiichi Unit 3
Swimming robot ‘little sunfish’ to inspect crippled Fukushima plant
Japan has unveiled a small swimming robot that will inspect the damage at the crippled Fukushima nuclear power plant. The device weights 2kg, is 13cm in diameter and will be able to swim deep into the melted reactor, its developers say.
The Japan-based International Research Institute for Nuclear Decommissioning (IRID) unveiled the robot, dubbed ‘mini manbo’ (little sunfish) in the media, together with Toshiba group on Thursday.
The robot “is small enough and resilient enough to enter and inspect the damaged primary containment vessel [PCV] of Fukushima Daiichi Nuclear Power Station Unit 3,” a statement from the IRID said, adding that the device will be deployed this summer.
The device is equipped with two cameras and can be remotely controlled via a wire, while operators can record its progress through the coolant. ‘Little sunfish’ will deliver a video feed that “will clarify damage to the PCV interior and information on how best to retrieve fuel debris,” the IRID added.
The major advantage of the robot is that it “can avoid various obstacles,” Tsutomu Takeuchi, a senior manager at the nuclear energy division of Toshiba, told AP. The company is tasked with helping to clean up the damaged plant.
The device was created for inspection of the primary containment vessel (PCV) of Unit 3 of the crippled plant. Unit 3 was flooded with coolant to a depth of about 6 meters (20ft) and in order to make a proper clean-up, such a coolant must be located and mapped, according to the IRID.
“The penetration hole giving access to the PCV is only 14cm in diameter, limiting the size of any robot that can be deployed,” the IRID added.
Thus, the newly-presented robot seems ideal for the job.
The robot’s radiation resistance is approximately 200 Sievert (Sv), according to its characteristics. For comparison, an exposure of about 1 sievert can cause biological damage to living tissue, according to the International Atomic Energy Agency (IAEA).
“Scientists developed ‘mini manbo’ with the aim of operating in a highly radioactive environment,” Goro Yanase, general manager of Toshiba’s Nuclear Energy Systems & Services Division, said.
“We succeeded in developing a small robot with high-level radiation resistance, and through its deployment we expect to get information that will support the advance of decommissioning,” he added.
The Fukushima Daiichi nuclear power plant suffered a blackout and subsequent failure of its cooling systems in March 2011, when it was struck by an earthquake and tsunami. Three of the plant’s six reactors were hit by meltdowns, making the disaster the worst since the Chernobyl catastrophe in the USSR in 1986.
Japanese authorities have repeatedly sent robots to inspect the contained area of the crippled plant but the devices either broke down or the missions were aborted. In February, such an attempt ended in failure as a clean-up robot stopped working two hours after it was sent to the inactive Reactor 2 at the nuclear complex.
Following the failure, Naohiro Masuda, president of Fukushima Daiichi Decommissioning, said that more creativity was needed to produce robots that can find and assess the condition of melted fuel rods at the high-level radiation site.
https://www.rt.com/news/392441-japan-underwater-robot-fukushima/
Toshiba unveils submersible video robot to probe reactor 3 at Fukushima No. 1 plant
YOKOSUKA, KANAGAWA PREF. – Toshiba Corp. unveiled on Thursday a submersible robot to take live video of reactor 3 at the Fukushima No. 1 power plant to confirm whether fuel debris is sitting at the bottom of a pool of radioactive water inside.
The location and condition of the fuel in the three reactors hit by core meltdowns is critical information for Tokyo Electric Power Company Holdings Inc., which runs the plant. Removing the fuel debris is considered the most difficult part of decommissioning the complex.
Unit 3 has the highest level of water inside at 6 meters. The fuel debris inside is presumed to have melted through its pressure vessel and settled at the bottom of its primary containment vessel.
“Until today, no one has seen the situation inside reactor 3,” said Tsutomu Takeuchi, senior manager at Toshiba’s Fukushima Restoration and Fuel Cycle Project Engineering Department.
“If we can observe the situation inside the reactor, that would be a huge leap in our ongoing effort to extract the debris” and eventually shut down the wrecked plant, he said during a demonstration of the robot at the Port and Airport Research Institute in Yokosuka, Kanagawa Prefecture.
Co-developed with the International Research Institute for Nuclear Decommissioning, the cylindrical 30-cm robot, dubbed the “mini manbo” (miniature sunfish), has a camera that can move 180 degrees vertically on its front and a fixed camera on its rear, allowing it to crawl through the water while capturing images.
Tepco plans to send the remotely controlled robot into the reactor as early as mid-July. A camera inserted into the reactor in October 2015 was unable to reach the bottom of the containment vessel.
No probe has been able to confirm the location or condition of the nuclear debris in any of the three crippled reactors.
Tepco sent a scorpion-shaped robot developed by Toshiba and the institute into reactor 2 in February, but it broke down before reaching its target under the pressure vessel after a tire got stuck.
In March, Tepco’s five-day robot-based investigation failed to capture an image of what was thought to be fuel debris in reactor 1.
A separate Tepco probe in January found black lumps in reactor 2’s pressure vessel but couldn’t immediately confirm they were fuel.
In December, the government estimated that the total cost of the Fukushima disaster would reach ¥21.5 trillion, including ¥8 trillion for decommissioning. That was almost doubled the initial estimate of ¥11 trillion.
Takeuchi of Toshiba did not reveal how much it cost to develop mini manbo.
Tsutomu Takeuchi, senior manager at Toshiba’s Fukushima Restoration and Fuel Cycle Project Engineering Department, shows off a robot it claims can probe water-filled reactor 3 at the defunct Fukushima No. 1 nuclear plant.
Swimming and wriggling robots unveiled for Fukushima clean-up
University and industry scientists have demonstrated new robots specialised for moving through and searching scenes of destruction that are impossible or dangerous for humans to enter.
Hardy, agile, remote-controlled robots will be vital for the decommissioning of power plants, particularly in the case of the Fukushima Daiichi Nuclear Power Plant, which suffered a meltdown in 2011 following a devastating tsunami and earthquake.
Robots can spend hours or days in environments so highly radioactive that a human worker would be killed in seconds.
The Japanese government hopes to start the challenging task of removing hundreds of tonnes of melted fuel after the Tokyo 2020 Olympics, potentially beginning work in 2021. For this to be possible, engineers need to know the exact location of the fuel, and understand the extent of the structural damage to the reactors.
Among other efforts, a snake-like robot was used in 2011 to explore the reactors, but was trapped repeatedly by obstacles and its camera was blocked. A “scorpion” inspired crawling robot also failed to navigate the site and was abandoned inside.
Years later, a new version of the snake-like robot has been revealed by Japanese scientists, including a team from Tohoku University in Sendai: a region severely affected by the tsunami and earthquake.
The robot stretches to eight metres in length, has a camera attached to the front and can move at speeds of up to 10cm per second.
It wriggles in a serpentine motion, propelled by the vibrations of the brush-like hairs that cover its body. Unlike any other robot, it can also “rear” its tip like the head of a snake, shooting a small jet of air to lift it. This allows it to climb over obstacles – such as debris in a disaster zone – up to 20cm in height.
According to Professor Satoshi Tadokoro of Tohoku University, the robot could search for people trapped in collapsed homes following earthquakes, and test the structural safety of damaged buildings. The researchers hope to have it ready to assist in search and rescue operations and other tasks within three years of durability testing.
Meanwhile, an alternative disaster relief robot has been unveiled by Toshiba and the public International Research Institute for Nuclear Decommissioning. This swimming robot is the size of a loaf of bread is and fitted with lights, camera and tail propellers.
It is designed specifically to inspect meltdown damage at the Fukushima nuclear plant, and will enter the primary containment vessel of Fukushima’s Unit 3 this summer to locate melted fuel in radioactive water.
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