Not sure if this is a positive but it certainly puts Fukushima into some perspective. The video takes a bit of time but is worth looking at.
http://www.ctbto.org/specials/1945-1...sao-hashimoto/
http://www.ctbto.org/press-centre/hi...-ctbto-page-2/
"...the levels detected at stations outside Japan up until April 13 have been far below levels that could cause harm to humans and the environment. The levels are comparable to natural background radiation such as cosmic radiation and radiation from the environment on Earth and lower than from manmade sources such as medical applications or nuclear power plants (under normal operations) or isotope production facilities"