A new monthly report has been added regarding the progress in Medium and Longterm Roadmap at
http://www.tepco.co.jp/decommision/planaction/roadmap/index-j.html
From the various files posted I find this one interesting as it announces
new investigation in PCV of Units 2, and some new results of the investigation into the PCV of Unit 3:
http://www.tepco.co.jp/nu/fukushima-np/roadmap/2017/images2/d171130_08-j.pdf
Page 5 (as indicated by the PDF reader): Some results of the past investigation in PCV of Unit 1 - Jan-Feb 2017.
Page 6: The newly planned investigation. They will use X-6 penetration and CRD rails, reach the grating again and aim to take a better look below the grating where it is possible to find nuclear fuel debris.
Page 7: Compared to last time they will modify/improve the telescopic arm used to gain access into the PCV. It will be longer and allow the deployment of an "investigation unit" which includes a camera. This unit will be lowered through the spaces created by the missing grating panels. The longer arm will allow a new better look above too, in the direction of the CRD housings.
Page 8 shows the way they will maintain a sealed boundary during the work to prevent any gas from inside the PCV from escaping outside (similar with last time).
Page 9 gives the schedule. After training and preparations the investigation is scheduled for end of Jan - beginning of Feb 2018.
------------
Page 11 (again, as indicated by the PDF reader; otherwise the page numbers start again from 1 in each report): Reminder of the past investigation carried out in July 2017 with the underwater swimming robot
Page 12: Top-left photo: Melted and resolidified material is stuck on the CRD flange. Photo below: the level and distances among neighbouring CRD flanges differs.
When the underwater robot peeked through the space between CRD housing towards the surface of the water, a disturbance of the water surface was observed in Area A1 as if water drops were falling in that place. There were several other areas where this was observed - as explained later in the report on page 14. Bottom-center photo: how the CRD housing area of Unit 3 looked before the accident. Top-right photo: CRD flange and PIP cable.
Page 13: Some more results. Melted and re-solidified material adhering to the support structure of the CRD housing in top-right photo. Top center: a presumed "CR guide pipe", broken, has been filmed near a CRD housing flange. The reasons they believe that is a "CR guide pipe" will be explained below in the report on page 16.
Page 14: Water surface disturbance has been observed in locations 1 to 4. The speculate that this may indicate the possibility that there is damage to the RPV not only on its bottom area, but also somewhere else along its body.
Page 16: Characteristics of the pipe observed: it has some sort of rod-like object in it, which has visible "notches" at regular intervals. At the time of the accident the CR were fully inserted and only the CR index tube was left inside the CR guide pipes. This indicates that the larger broken pipe is a CR guide pipe (diameter 28 cm) and the rod-like object inside, with notches every 15 cm, is a CR index tube.
CR guide pipe is made of SUS304 stainless steel that melts at ~1450 deg C. CRD index tube is made of nytrogen-treated (?) XM-19 stainless steel with similar melting point.
Page 17: careful evaluation'estimation of the distances between notches and sizes of various elements seen in these images support the same conclusion regarding the "identity" of these parts.
Page 18: In area designated B1 they cannot confirm the presence of the expected grating. Structures below grating are visible. So the grating must have fallen from that area.
Page 19: The circular rails used to rotate the platform inside the PCV are preserved. Deposits can be seen on the brackets that hold the rails.
Page 20: The surface of the pedestal walls (on the inside) shows scaling off of the epoxy layer as well as some rougher surfaces but no large-scale damage or deformations.
Page 21: Inside the pedestal. Deposits like small rocks can be observed in area C1. Sand-like deposits and fallen grating in area C2. Boulder-like deposit in C3 and C4.
Page 23: They revisit the "water surface disturbances" issue. The blue areas show the places where these disturbances were observed. The red areas show places where they identified damage of CRD housings and adjacent structures.
Page 24: This diagram shows the approximate location of various objects and deposits observed on the bottom inside the pedestal, yellow circles depicting the location of the big boulders.
Page 25 combines the contents of pages 23 and 24.
Page 26 speculates on the nature of some other fallen objects seen inside the pedestal, showing similarities to parts of a Control Rod. A definitive conclusion could not be drawn though because they couldn't find the most distinctive part, the umbrella-like "speed limitor in case of the falling of the control rod" (sorry I have some trouble translating this one).
Page 27 speculates that another object could be the upper "tie plate" (definitive conclusion was not possible). It could be from a A-type 9x9 fuel unit, or from a MOC unit, or from a so-called "dummy fuel unit".
Page 28 and 29: some more tubular objects that resemble CR guide pipes.
Page 30: at about 270 degrees om the pedestal inside wall some damaged cables are observed, probably destroyed by flowing molten material (some of it adhered and solidified here).