I found some much needed factual information on this issue on the Deep Sea News website. It pretty much debunks all the scary-scary stuff posted here, there, and thither by people who make it a business to scare people.
Author Kim Martini, PhD, is a Physical Oceanographer at the Joint Institute for the Study of Atmosphere and Ocean at the University of Washington.
She attacks such topics as "The Three Maps of Terror"... I especially appreciated that she discovered that "MAP OF TERROR #1: The Rays of Radioactive Death!," which I've seen in several publications isn't even a map of radiation at all. It's actually a completely mislabelled map of tsunami wave heights. In other words, the map as presented is a complete fraud, being propagated as part of a bogus alarm.
Other fun topics include: What's a Bequerel? What's a Sievert?; Simpson's Guide to Radiation; and finally the Really Big Two: Will the radiation reaching the West Coast be Dangerous? and Can I eat fish from the Pacific? <spoiler alert: no, and yes>
True facts about Ocean Radiation and the Fukushima Disaster | Deep Sea News