Nukes disperse less radioactive material than Fukushima because bombs are very efficient converting matter into energy so it’s mostly heat, light sound etc.
There was actually a sizable discharge of radioactive waste into the ocean re Fukushima and scientists were tracking it. Given that the northern oceanic gyre sweeps up the coast of japan to china, across the Aleutians and then down the coast of the US, I was initially shocked to see that the dense plume of radioactive wastes was transiting the ocean pretty much from east japan to west US. But of course, that would be due to the rotation of the earth - similar to the way that the jet stream blows across the US in that same direction.
This article details how some researchers tested 15 bluefin tuna from the docks in San Diego in hopes of detecting radioactivity from Fukushima in August of 2011 (5 months after the meltdown). They thought that any radioactivity would have dissipated by the time the bluefin tuna crossed the Pacific Ocean. They were wrong - all 15 of the bluefin tuna they tested had significant amounts of radiation. Score! Unless you are someone who doesn’t like to eat radiation in their tuna!
http://articles.latimes.com/2013/may/08/science/la-sci-fukushima-radiation-20130225
In terms of longitude, a radiation “front” (radioactive wastes carried by ocean currents) had made it half way from Japan to the US in March 2012 (about 180 degrees longitude). It should have made it about here by now, eh?
Stop your silly scare-mongering.