Unit 1 Torus Inspection Review

New work done around February 21 to 22 has been posted by TEPCO and confirmed by workers.

The newest work was done at a new location about 17 meters from the previous torus inspection location.
(ignore the blue route lines, those are from a previous use of the floorplan diagram at another unit.)
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The video was considerably different than what was seen on the previous torus inspection.
The newest inspection video can be found here on our Youtube channel

Our work and data from the previous torus inspection back in June 2012 can be found here.

We also processed the new inspection video into individual images that can be found on our Flickr page.

Two TEPCO handouts from the newest torus inspection:

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Workers drilled a large hole into the concrete floor in the north west corner of the 1st floor of unit 1. They inserted a scope with a camera, temperature probe, radiation detector and a tool to remove a sediment sample available for their use.
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Workers use a mirror to see down into the hole in the floor. Worker on the right wearing what looks like a lead or titanium vest for additional protection.

While workers conducted the tasks they grabbed a sediment sample from the bottom of the torus room. The new video found some of what was seen on the earlier video that looks almost like sand and fine debris inside the torus room floor.

U1_torus_sedimentbottle130222_05

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Sediment found in the torus room floor.

The images from this inspection showed much more than the previous one. The quality is much higher and lighting better. They were able to catch some pieces of equipment that still need to be identified, a good view of the torus tube, some pumps for the emergency cooling systems and a torus downcomer pipe.

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The pump located nearby

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This section of wall and steel appears to be corroded or scorched.

Surface of the torus tube. The same tube seen in unit 2 appears to be painted a reddish color.

Manhole cover and pipe in the foreground, torus downcomer in the background center of the photo.

The water surface in the torus room is milky and opaque. Worker “Happy” mentions about a 60cm “turbidity”, possibly the distance that can be seen in the water

The exact causes of the debris and sediments in the water are currently unclear to their origin. The sediment sample had a radiation reading of about 4mSv/h outside the bottle. The highest radiation reading found on this inspection was 920 mSv/h right above the water surface. The previous readings at the other location in June 2012 were considerably higher with levels lower in the water outside the capability of the meter used. The region of the newest inspection also appears to be in better condition than the June 2012 inspection location.

Worker “Happy” cites the readings were the highest close to the torus tube and he thinks that may be the source.
the flow of water was not because they look like, It may not be close to where it leaks. Rather than a dose of water next to the tube torus is also the location of the measurement point because 920mSv / h dose, I think the influence of the tube torus. That’s the same effect, but also on the catwalk high dose.

He goes on to mention a concept we have considered for a long time and that TEPCO has given more attention to, that melted fuel likely found its way into the torus tube.

Because I think I may have fallen into the tube torus meltdown of the fuel through the downcomer continued issue 3:1, from among persons of influence is large. Water dose was lower than expected OIRA. I do not know just one place the survey, if the dose effect from the torus tube, you can do the following: I have seen.”

Happy also mentions that the torus tube needs further inspection but they currently do not have a viable plan to do so due to the high radiation levels or a way to place robots into the area.

 

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