Fukushima Unit 2 Scorpion Probe Dies But Sends Back Some Data

While the press reported Scorpion’s mission as a failure, it provided useful data before being abandoned. It collected some radiation readings and a number of useful images.

The robot seems to have become stranded on a pile of debris on the rail. Radiation data from along this inspection route provided only one radiation reading, no telemetry as other videos had. Tepco’s video is heavily edited but still provides some useful information.

A reminder, these readings are the result of venturing into the more deadly areas of the reactor where they have been unable to previously, no resulting from an increase of radiation. While this is much lower than the earlier camera estimates of radiation it is still extremely high and quite deadly.

Arond the same area where the high radiation source was found, TEPCO stated they found a 210 Sv/h reading with the on board radiation sensor.

New images from inside the pedestal were obtained as were some images looking up into the containment structure.

Image below from TEPCO. White ghosting on the image is likely due to radiation levels rather than steam. The existing melt hole in the pedestal floor grate can be partially seen in the upper mid section of the image. A very thick amount of fuel debris can be see in the lower right section of the image. The mark “clean” on this image with an arrow indicates an area where the floor grate may have failed after the molten fuel had splattered on the area. Further below, more fuel debris and structures can be seen.

The red circle shows an area where it appears fuel debris was moved or blocked by a fallen piece of sheet steel.

In both images, sections of light colored piping can be seen below the area where the grate is missing. On the far left of the image a partially melted section of flexible conduit can be seen.

This appears to indicate that high temperatures within the pedestal were very localized.

Sources:

TEPCO handout for this work

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2017/images/handouts_170216_01-e.pdf

February 18, 2017 - Posted by dunrenard | Fukushima 2017 | Fukushima Daiichi, reactor 2, Scorpio Robot