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How Work To Remove A Radioactive Tower At Fukushima Daiichi Went Wrong

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June 12, 2019
Measure twice, cut once.
 
Work to remove the highly contaminated units 1-2 vent tower at Fukushima Daiichi took an unfortunate turn last month. The cutting rig had been tested at one of the research facilities and was determined ready to use. When the equipment was assembled on site and work was to commence, it was discovered the crane and cutting rig could not be lifted high enough to place it in the vent tower stack.
 
With the work now on hold, contractors involved tried to determine what went wrong. Three issues were found that created the cascading error.
 
The cables that attach the cutting rig to the crane were longer in real life than they were in the on paper design. This caused the cutting rig to sit 3 meters too low.
 
The crane being used on site was slightly different than what was assumed on paper, this impacted the height the rig could be lifted to.
 
The engineering survey of the site and ensuing blueprints incorrectly interpreted the total height of the tower by 1 meter. This was due to portions of the base and attachment of the vent tower on site being miscalculated. The base of the tower is obscured by concrete slabs and other shielding put in place after the extent of the dangerous radiation in the tower was better understood.
 
The solution to part of the problem is to position the crane closer to the tower. This requires the addition of gravel fill to the area to provide the crane a elevated area to sit upon.
 
The series of miscalculations will cause the work to cut down the vent tower to be delayed until late July 2019.
 
Read more: simply Info
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June 27, 2019 Posted by | fukushima 2019 | , | Leave a comment

TEPCO’s Plan For Some Of The More Dangerous Work At Daiichi

Soon after the disaster workers at the plant discovered that their dosimeters would high radiation alarm then be unable to give a reading when they approached the unit 1-2 shared vent tower. This was an indication that radiation levels near the tower were so high that their dosimeters were unable to accurately read the level. One of the most dangerous places at Fukushima Daiichi may undergo work to reduce the ongoing risk.

One of the two units connected to this vent tower ejected considerable amounts of radioactive materials via the tower during the initial disaster. The area has been declared off limits with shielding walls installed. Closer inspection with cameras and drones showed that the tower had suffered structural damage and was at risk of collapse or further damage. Since then TEPCO and the research agencies tasked with disaster clean up at the site have been working on a plan to dismantle the tower.

The current plan includes a complex series of machines and equipment designed specifically for this task. The work would remove the upper portions of the vent tower then install a cap on the top of the remaining pipe. This is assumed to be used to prevent further release of radioactive materials or inflow of rainwater into the highly radioactive area. The actual demolition work is scheduled for fall of 2018 and could take a year to complete.

The graphic below shows the steps towards cutting down the tower in sections.

u1_2_vent_tower_dismantling 24 july 2018.jpg

 

August 1, 2018 Posted by | Fukushima 2018 | , , | Leave a comment

Drone Inspection of Fukushima Units 1 & 2 Vent Tower

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TEPCO reported on October 20th they used drones to measure radioactivity at the  reactors 1 and 2 vent tower.

Vent towers are quite unstable during earthquakes and are highly contaminated, they are therefore not easy to dismantle, even with robot

When they sent a drone into the vent tower, they found out that a bar prevented the drone to go in lower than 10-20 m below.

It’s pretty amazing that Tepco did not know that this bar was there and that they can not give its position more precisely.

TEPCO only  provided two pictures online with a laconic comment. No results of their radioactivity measuring was given. Transparency is progressing …

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2016/images/handouts_161020_02-e.pdf

October 25, 2016 Posted by | Fukushima 2016 | , , , , , | Leave a comment