Watch the flashes in these videos. In the first video they start at 1:40
In the second video there are many in the first 3 minutes
The flashes appear to be coming from behind 1 and from the area of units 3 and 4.
When I looked at the Tepco webcam this morning (9:00 am Arizona time) there was massive steam everywhere. The steam disappeared within 2 minutes. http://www.tepco.co.jp/nu/f1-np/camera/index-j.html
Now at 10:30 am the steam is building back up again; it is coming from the area of units 3 and 4.