It is good to see the shield plug, presence of which should indicate that the Reactor 3 explosion was probably not nuclear as many people have postulated.
TEPCO has been clearing the debris from the Reactor 3 operating floor since September 2012, in preparation of debris removal from the Spent Fuel Pool.
Then in December 2013, with hardly any fanfare or press coverage, TEPCO started removing the debris, starting with the small pieces, from the Spent Fuel Pool, using remote-control heavy equipment (see my 1/1/2014 post).
If the SFP debris removal is on schedule (which may not be, because of the heavy snow in the past two weeks), TEPCO should be just about ready to remove the Fuel Handling Machine.
The video was taken on January 31, 2014 from a camera fitted on the boom of a crane.
From TEPCO's photos and videos library, 2/14/2014:
The entire operating floor (click to enlarge; composite photo from several photos, according to TEPCO): Upper left - DSP (Device Storage Pit), upper center - Reactor Shield Plug, upper right - Spent Fuel Pool
On October 10, 2013, the operating floor was covered with smaller debris. The shield plug was not discernible:
FYI, on March 24, 2011, it looked like this:
In the latest photo, the shield plug appears intact, but if you look closely the center of the middle piece is depressed downward. TEPCO's analysis is that some heavy debris fell on top of the piece after the explosion, and the shield plug itself (which has three layers) is structurally sound. The shield plug is not likely to be touching the Containment Vessel head, says TEPCO in the accompanying document.
Again from TEPCO's photos and videos library, 2/14/2014, photos of the shield plug, with the second photo showing the gap of 300 millimeters (or 30 centimeters):
Diagrams of the shield plug, and TEPCO's analysis on the deformed shield plug, from the accompanying document (Japanese):
(TEPCO's analysis above)
The cause of deformation could be "hydrogen explosion" or "falling of the ceiling crane and other objects". However, as the floor slab (30-centimeter and 60-centimeter thick) surrounding the shield plug is not damaged, it is not likely that the shield plug (made of three layers of ferroconcrete (60 centimeters each) was deformed by the hydrogen explosion. The ceiling crane itself did not make direct contact with the shield plug after it fell, but there was a trolley above the shield plug. So the deformation is likely to have been caused by the fall of the main hoisting hook onto the shield plug.
The first diagram shows (on the left) that there is a 1,200 millimeter (1.2 meter) gap between the bottom of the third layer of the shield plug and the Primary Containment Vessel head. TEPCO doesn't seem to think the mid and bottom layers were damaged and causing damage to the Containment Vessel, and cites the results of dust sampling and air dose rate measurements on the shield plug and surrounding area as evidence (no significant difference in radioactivity).
The location where the steam have been seen rising, from TEPCO (7/24/2013):
The video taken on 1/31/2014:
The most severe damage, on concrete floor at least, is not seen near the shield plug or the Spent Fuel Pool on the east half of the operating floor but in the northwest corner (bottom left in the overall photo, or in the video showing the entire floor in the beginning). I wonder what was there (or the floor below).
For the changing look of the Reactor 3 operating floor, see my post on 12/31/2013.