Okay, taking this seriously...at least with just the MEREST touch of humor....
Picture the reactor in Japan as a tophat type of Polish rooster. A really, really BIG one, but a tophat type of Polish rooster nonetheless.
You know how their crest grows UP, then each feather tips over sideways of its own weight? Picture those as the radiation plumes from the plant.
To tip over and reach out sideways, they have to be a certain length and thickness. Then they tip over, and then downward, right?
Okay.
Now, to put this in perspective, if the reactor fuel is the chicken's brain (come on, folks, use that imagination!
), and the feathers are the radiation, which is thickest closest to the skull (containment vessel), then you're looking at the most likely distribution of radioactive material.
Not much of it goes very far, does it? Oh, you'll get a few longer feathers to make a nice fringe, but you generally get a mop-headed type of look, right?
So....proportionately speaking...
If I'd ever seen a topknot that is 3 FEET in diameter AND that reaches the ground that far out, on a normal-sized chicken, then I'd be worried.
Now, honestly, what are the odds, even in a high wind, of getting such a thing? And then add rain to the equation, which helps dampen down radiation and carry it to the ground?
Your chicken would be pasted to the pavement in short order, now wouldn't it...?
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Seriously, that's what the picture is like. The most radiation is most likely to be very near the plant. Unless there is some kind of absolutely hellacious explosion that shoots radioactive material at LEAST six miles up (that's MILES, like some 30,000 feet and more!), the air currents which are capable of reaching even Hawaiii won't pick up enough gamma-emitting material to worry about.
Yes, it's possible that radiation will reach the West Coast states/areas. But possible does NOT mean probable, and how MUCH radiation, as well as what KIND of radiation, makes it that far is what will make the difference between 'harm and a simple temporary rise in background count that does no harm at all.
So, please, folks...if you are truly worried, PLEASE do your research and relax until there is truly cause for realistic worry, okay?
There are a couple of links I found in my travels to research this for my own benefit and for other groups I moderate that I think are helpful:
http://www.nrc.gov/about-nrc/radiation/health-effects/measuring-radiation.html
http://www.nrc.gov/about-nrc/radiation/health-effects/radiation-basics.html
http://orise.orau.gov/reacts/guide/definitions.htm
https://orise.orau.gov/reacts/resources/radiation-faq.aspx