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