While many people assume that the ocean will dilute the Fukushima radiation, a previously-secret 1955 U.S. government report concluded that the ocean may not adequately dilute radiation from nuclear accidents, and there could be “pockets” and “streams” of highly-concentrated radiation.

 

The University of Hawaii’s International Pacific Research Center created a graphic showing the projected dispersion of debris from Japan:

 

Last year, scientists from the National Oceanic and Atmospheric Administration’s (NOAA) Pacific Marine Environmental Laboratory and 3 scientists from the GEOMAR Research Center for Marine Geosciences showed that radiation on the West Coast of North America could end up being 10 times higher than in Japan:

After 10 years the concentrations become nearly homogeneous over the whole Pacific, with higher values in the east, extending along the North American coast with a maximum (~1 × 10−4) off Baja California.