For a detailed account of what happened in the Fukushima Daiichi facility, see:
http://www.world-nuclear.org/info/fukushima_accident_inf129.html

For an assessment of lingering danger, see:
http://articles.latimes.com/2012/mar/11/opinion/la-oe-gale-fukushima-20120311

A comprehensive summary by The New York Times of the Japanese enquiry into the Fukushima accident can be found at:
http://www.nytimes.com/2012/07/06/world/asia/fukushima-nuclear-crisis-a-man-made-disaster-report-says.html?_r=0

There is a huge quantity of naturally radioactive elements in the oceans, and some can be harvested:
http://www.newscientist.com/article/dn22201-record-haul-of-uranium-harvested-from-seawater.html

For the effect of the fallout from Fukushima Daiichi on California, see:
http://abcnews.go.com/blogs/health/2011/09/21/fukushima-fallout-in-california-waters-a-threat/