Bueno - Are you serious?  What info don't you understand?  the 400mSV is not a problem?  These guys are directly in this to fight this battle. TEPCO sent everyone home except these 50 people. Do you really think there is a lack of work to do that only these 50 people are needed? They are the sacrificed to try and save the rest in Japan.
Do you really think these people will not have serious health problems (or death) going forward?
I get it you think I am wearing a tin hat.  But some of you people are in serious denial.  There has been a breach (or multiple breaches).  The radiation levels are extremely elevated at the facilities (hence the widening of the perimeter, sending people home, change in tone from Japan's officials, advising people to remain indoors at all costs, etc).
		
		
	 
David....Bueno has been 100% correct in his posts, and seems more familiar with commercial plant design than I am (I was Navy). You are wearing the foil hat.Nuclear Power facilities have ALWAYS operated under a cloud of suspicion and a litany of over-bearing safety precautions. The public has remained largely ignorant both of Nuclear power and of what radiation is, how it works, and what it can do. People have ALWAYS over-reacted to anything "Nuclear".
These problems are serious, but this is not now, nor will it ever progress to anything remotely close to Chernobyl. The overhwhelming majority of the precautions taken by the Japanese gov't are just that...precautions. If someone's lifetime cancer risk could have quantifiably been raised by even 1/2 of 1%, and they DIDN'T take these precautions, they'd be eviscerated later.
Radiation levels 20 feet outside of an operating power plant are NORMAL...IE: No differant from anywhere else. A "significant rise" to even 10X normal would not pose a risk. 100X normal would remain a manageable risk.
TAKE OFF THE HAT!