It's so slow that nothing seems to have been happening.
March 15, 2011, the day Reactor 4 had an explosion. At that time, "fire" was emphasized not "explosion", and the condition was described as "a hole in the wall, and damage to the ceiling". More accurate would have been "8-meter hole in the wall that is crumbling, and no ceiling except for steel beams."
March 16, 2011:
March 22, 2011:
March 24, 2011:
April 10, 2011:
June 10, 2011:
January 5, 2012. This photo caused some bloggers and sites to claim Reactor 4 is falling apart. For more about the demolition/cleanup work that was being done, see my post from December 2011:
February 24, 2012:
March 5, 2012:
Photos are from TEPCO's "Photos for Press" page for Reactor 4.
Long, long way to go.
Ironically, the cleanest photo of the recent Reactor 4 building was presented by Asahi TV's "Morning Bird" program on March 8, 2012 that seems to have introduced many Japanese (and non-Japanese) to the Reactor 4 Spent Fuel Pool danger for the first time after more than 1 year since the start of the accident, however erroneously. The aerial photo of Reactor 4 building was presented as "walls all gone, they were all blown off in the explosion". Well not really. That photo was after the clean-up of removing most of the crumbling wall panels and part of ceiling beams to remove the crane: