...Specifically, MOX fuel refers to a blend of plutonium and natural uranium, reprocessed uranium, or depleted uranium. ...reactors that predominate nuclear power generation...
here...Unless you are in the 50-mile zone around the reactor you may not have much to worry about. It is the perhaps the most powerful of the fuels in use there, and something they may well be concentrating on - i.e. why they dropped water on that and 4.
Most of the sources I have read say unless the core on #3 blows up and spews plutonium into the air, the risk from that fuel in the U.S. is minimal, at least from Japan. There is little discussion of the steam that is coming out, and even though contaminated most likely would not rise to the level of jumping on the jetstream and hitching a ride to Seattle. That still leaves the products of the accidents at the others, not likely to be as hazardous this far away.
The biggest problem is likely to be in that 50 mile radius around the plant. For 800 years or more.
Be optomistic about this, unless you see a reactor blow up and fly into the sky. I suspect our government is monitoring this, and if there was anything much greater than the normal radiation we eat, and use to see broken bones, get while flying, etc, they would be all over us about stockpiling duct tape and plastic sheeting. Again. I don't see the upside for them to let a lot of people get sick the year before and during an election. The only group that might see the good side of that is the Westboro Baptist Church, and they are delusional.