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Fukushima Daiichi contaminated exhaust stack disassembled

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Fukushima Nuclear Power Plant Contaminated Exhaust Chimney Disassembled

April 30, 2020

The disassembly work on the radioactively contaminated exhaust chimney of the Fukushima nuclear power plant is finally complete after 9 months of work. But the complete decontamination of the plant is expected to take decades.

https://www.nippon.com/en/news/ntv20200430001/fukushima-nuclear-power-plant-contaminated-exhaust-chimney-disassembled.html?fbclid=IwAR0d2x1abJgzILGy6YyppKEhraIyiPcQ0PnfTEvmQP-AVo8LwaDMWIZIxa4

 

Contaminated exhaust stack at Fukushima plant finally cut in half

jlkklmùmA contaminated exhaust stack at the Fukushima No. 1 nuclear power plant in Okuma, Fukushima Prefecture, is dismantled on April 29.

 

April 30, 2020

OKUMA, Fukushima Prefecture–Work to dismantle the upper half of an exhaust stack at the crippled Fukushima No. 1 nuclear power plant finished on April 29, the first time a structure highly contaminated by radiation was dismantled at the plant.

The chimney, which is 120 meters tall and about 3 meters in diameter, was used for the No. 1 and No. 2 reactors of the plant, operated by Tokyo Electric Power Co.

On the morning of April 29, workers spent an hour to lower sliced parts of the stack to the ground from a height of about 60 meters. With its upper half removed, the chimney now stands 59 meters high.

I think there are still many things left that local companies can do,” said Isamu Okai, 52, a board member of local construction company Able Co., which carried out the work. “We want to continue our involvement in the decommissioning of the plant by making use of the expertise we gained from the dismantling work.”

When the nuclear disaster occurred at the plant in March 2011, vapor containing highly radioactive substances was released through the stack. But it raised concerns that the unstable chimney could collapse.

During the dismantling project, which started in August, workers remotely operated cutting equipment hoisted by a huge crane to reduce their exposure to radiation. They carried out the operation at a remote control room set up in a large remodeled bus on a hill about 200 meters from the site.

They faced many problems during the project. Rotary blades attached to the equipment wore out faster than expected, and telecommunications between the equipment and the control room frequently disconnected. The work had to be suspended every time a problem occurred.

As a result, it took a month to slice the uppermost part of the stack, which is about 2 meters high and weighs around 4 tons. That work was initially planned to be completed in a day.

In December, the rotary blades stopped working, forcing workers to be lifted on a gondola to slice the stack with an electric power tool at about 110 meters above the ground.

The work, however, went smoothly from the middle stage of the project. Workers replaced the blades with more durable ones and improved the way they sliced the stack as well as the stability of telecommunications.

http://www.asahi.com/ajw/articles/13339580

May 14, 2020 Posted by | Fukushima 2020 | , , | Leave a comment

Fukushima Liquidators Are Real

The robotic equipment failed. So they sent up humans for 4 days to finish the job.
Tepco needs a serious review over the initial dismantling plan for Fukushima.

 

01Fukushima: Tepco sends workers to repair where robots failed. High radiation.

Some weird stuff is happening at the TEPCO’s Fukushima Daiichi Nuclear Power Plant right now. While Japan has decided to drop radioactive water in the ocean, Tepco sent humans to repair where robots failed.

On December 3, workers were sent to the top of the exhaust stack (about 110 meters high) standing beside the Unit 1 and 2 buildings to finish cutting a cylinder body with an electric tool after the robotic infrastructure failed.

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The workers at the top of 110-m high Fukushima Dai-ichi vent stack were exposed to an estimated 810 μSv, making this action an emergency response.
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But officials first said radiation would not be above 300 μSv:
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According to TEPCO, the workers cut 1.1 meters out of the remaining 1.3 meters. The work resumed on Dec. 4 early morning due to forecast of strong winds.
 
Within the six hours of work, the workers were wearing masks covering their entire face to protect them from radioactive substances. According to officials, they were exposed to a maximum dose of 0.47 mSv.
 
The cylinder body of the exhaust pipe will be cut into 2-4 meter pieces at a time and should be halved around next March (60 meters). Let’s hope that the robotic saw blade will not fail again!
 
Meanwhile Fukushima radiation dust is still coming in… And that’s not good for the Olympic Games 2020:
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December 24, 2019 Posted by | fukushima 2019 | , , | Leave a comment

Section of exhaust stack at nuclear plant removed

Work that was expected to take two days ended up taking a month. They were initially delayed because the crane wasn’t tall enough!? Good grief. Pretty hard to believe that their engineers/decommissioning crew aren’t working together enough to figure something as simple and basic as that out in advance. Work of this “quality” certainly doesn’t instill a lot of confidence in their ability in their decommissioning efforts.
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September 3, 2019
 
Workers have finished removing the top section of an exhaust stack for two damaged reactors at the Fukushima Daiichi nuclear power plant.
 
The plant’s operator, Tokyo Electric Power Company, is working to dismantle the upper half of the 120-meter-tall stack.
 
It has released footage of the work completed on Sunday, about a month behind schedule.
 
The workers used a crane to lift off a section of the stack, together with the equipment used to cut it, and lowered them to the ground.
 
The stack was contaminated by radioactive gases released after the 2011 accident and is at risk of collapsing in an earthquake.
 
The iron framework that supports the stack was also damaged in the accident.
 
The company plans to complete the work by the end of March.
 
Removing the first section was originally scheduled to take two days but ended up taking over a month to complete.
 
The work was initially delayed when it was discovered that the crane wasn’t tall enough.
 
Equipment failures and other problems created further delays.
 
Officials say they will study the work done so far in order to streamline the demolition process.
 

September 8, 2019 Posted by | fukushima 2019 | , , | Leave a comment

Work begins to topple dangerous exhaust stack at Fukushima plant

Dismantling work begins Aug. 1 to slice a highly contaminated exhaust stack into parts at the stricken Fukushima No. 1 nuclear power plant complex.
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A crane hoists a dismantling mechanism to the top of an exhaust stack at the Fukushima No. 1 nuclear power plant site.
 
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Work begins Aug. 1 to dismantle an exhaust stack at the Fukushima No. 1 nuclear power plant site.
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A crane lifts a dismantling mechanism toward the top of an exhaust chimney on the Fukushima No. 1 nuclear power plant site
 
August 2, 2019
Delicate work got under way Aug. 1 at the crippled Fukushima No. 1 nuclear power plant to dismantle an unstable exhaust stack that is so highly contaminated by radiation the task must be done by remote control.
Initial plans had called for the work to start in March, but the project was delayed by a failure among other things to confirm design plans that led operator Tokyo Electric Power Co. to deploy a crane that was not up to the task.
The exhaust stack, which is 120 meters tall and 3.2 meters in diameter, was used for the No. 1 and No. 2 reactors.
The work is regarded as a crucial phase in the decommissioning of the plant, a task that is projected to take decades and cost billions of yen.
When the nuclear disaster unfolded in March 2011, vapor containing highly radioactive substances was released through the stack. Metal poles used to support the chimney were found to have been damaged following a hydrogen explosion at the No. 1 reactor.
Radiation levels around the base of the stack are believed to be still too high for humans to work in, so the dismantling work must be done by remote control.
There are also concerns that the chimney could collapse. TEPCO plans to dismantle the upper half of the structure by the end of the current fiscal year.
A remote control room was set up in a large remodeled bus located about 200 meters from the site. Workers will operate the special cutting equipment while watching footage from 140 video cameras.
Immediately after the triple meltdown at the Fukushima No. 1 plant, radiation levels at the base of the chimney exceeded more than 10 sieverts per hour. In 2015, radiation levels still hovered at 2 sieverts per hour, the highest among all outdoor areas of the plant.
A 750-ton crane is being used to hoist the dismantling mechanism over the exhaust chimney.
The work was supposed to begin around 7:30 a.m. on Aug. 1 with the cutting of ladders and electric cables at the base of the chimney. But some of the equipment did not function properly because of problems with a telecommunications system.
Work finally started around noon.
From Aug. 2, the dismantling mechanism will be used to slice parts of the chimney from the top. The dismantled pieces will be stored in the grounds of the Fukushima No. 1 plant.
Although plans call for dismantling the upper part of the stack by the end of March 2020, strong winds and other weather conditions could cause delays.
The dismantling mechanism was developed and is being operated by construction company Able Co., based in Okuma, Fukushima Prefecture, where the Fukushima No. 1 plant is located.
It is unusual for a local company to be involved in such a key project on-site, but a company official said, “As a local company, we want to respond to the expectations of the local community by successfully completing the project without incident.”

August 3, 2019 Posted by | fukushima 2019 | , , | Leave a comment

TEPCO postpones work to remove exhaust stack at Fukushima plant

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The exhaust stack for the No. 1 and No. 2 reactors at Fukushima No. 1 nuclear plant will eventually be dismantled using equipment seen on both sides
May 17, 2019
Tokyo Electric Power Co. has delayed the start of work to dismantle a dangerous and highly contaminated exhaust stack at the Fukushima No. 1 nuclear power plant because of a calculation error.
The company said May 16 that work on the 120-meter-tall chimney, which was initially scheduled to begin on May 20, will be postponed until June at the earliest.
TEPCO found that the height of special cutting equipment lifted by crane would be 1.6 meters lower than under the original plan, making it unable to reach the top of the stack.
“We believe that the lifting angle of the crane arm turned out to be different from the original plan because of an error in measuring equipment,” a TEPCO official in charge of the operation said.
The company is now considering adjusting the angle and the crane position or extending the arm length after it is lowered.
The exhaust stack was used for the No. 1 and No. 2 reactors at the plant.
When the nuclear disaster unfolded in March 2011, vapor containing highly radioactive substances was released through the stack. Metal poles used to support the chimney were damaged apparently by a hydrogen explosion.
The area around the base of the stack contains levels of radiation that are too dangerous for humans to work in, so the dismantling work will be conducted by remote control.

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

Local firm to take on hazardous demolition at Fukushima plant

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A crane and equipment used for training to demolish an exhaust stack in Hirono, Fukushima Prefecture
April 11, 2019
OKUMA, Fukushima Prefecture–Work will soon start at the crippled Fukushima No. 1 nuclear power plant to demolish a 120-meter-tall exhaust stack that has kept workers at bay due to high radiation levels.
Given the hazardous nature of the project, Able Co., the local company that will undertake the task, will use remote controlled equipment deployed on a 750-ton crane to “slice” through the upper half of the structure.
The work will begin in May at the earliest and is expected to take up to six months. It is regarded as a crucial phase in the decommissioning process of the plant’s reactors.
The exhaust stack was badly damaged in a hydrogen explosion caused by the nuclear accident following the 2011 Great East Japan Earthquake and tsunami.
A 2015 survey showed radiation levels of 2 sieverts per hour around the stack, sufficient to kill anybody who spends more than a few hours in the area.
Able, originally headquartered just 2 kilometers from the nuclear plant, put together a special squad for training last autumn.
There are four exhaust stacks at the plant designed to ventilate reactor buildings.
The stack to be demolished is situated between the No. 1 and No. 2 reactor buildings. Its upper part was damaged when the No. 1 reactor building blew up on March 12, 2011.
The inside and outside of the stack were heavily contaminated because Tokyo Electric Power Co., operator of the plant, used it to release highly radioactive gases to lower pressure inside the reactor during the nuclear crisis.
Some parts of the exhaust stack are badly compromised. The Nuclear Regulation Authority noted that the structure would pose a danger if it fell.
TEPCO asked Able, which has been involved in regular reactor checkups and piping work at the nuclear plant, to demolish it. Able developed special equipment to cut the upper part of the exhaust stack with a rotary cutter.
At one point, the company considered using a hydraulic or laser cutter, but decided not to for fear of increasing the volume of radioactive water or triggering a fire.
“We are a construction company, so we concentrated on combining technologies to deal with the issue, not producing equipment from scratch,” said Tetsuo Sato, 45, leader of the on-site project team.
The demolition equipment will be manipulated remotely from a control room in a converted bus.
One fear is that strong gusts of winds could affect the operation. Workers will operate the equipment by watching images captured by 160 cameras mounted on and around the device.
Able has switched its headquarters to Hirono, also in Fukushima Prefecture, as a temporary measure. About 70 percent of its 200-strong work force hails from the prefecture.
The exterior of the bus is festooned with messages by children of employees, such as, “Be careful” and “Operate safely.”
“We, as a local company, want to bring back peace of mind to residents by completing this task successfully,” said Isamu Okai, 51, who oversees the demolition project.

April 14, 2019 Posted by | fukushima 2019 | , , | Leave a comment