http://www.youtube.com/watch?v=x5tZi-eO-_I&feature=youtube_gdata_player
No offense, but the source of that video is a hack. The image he uses of the steam is from April 2011.
It's this kind of crap that makes it so difficult to glean real info out there.
Radiation is not always observable. The amount of steam, in itself, means nothing.