On March 11, 2011, the world watched in horror at the series of unfolding events following a massive M9.0 earthquake off the eastern coast of Japan. A country with a modern and extensive nuclear power program was crippled first by the shaking and then a rapid influx of water from the subsequent tsunami. The Fukushima Daiichi Nuclear Power Plant sustained significant damage after the disaster, and while the vast majority of deaths and injuries from the March 11 disaster where from the earthquake and tsunami themselves, the nuclear accidents that followed represent today one of the most significant visible legacies of the tragedy. With many unable to return to their homes because of radionuclide deposition, significant groundwater flow through the Fukushima Daiichi site, and a vast source term of spent and damaged fuel assemblies to be removed, the nuclear accidents at Fukushima represent an element of the 2011 Tohoku earthquake that is still unfolding.
In the 3 years since the accident at Fukushima, I have seen no significant radiological impact outside of Japan and it's immediate coast. You can see below an archive of monitoring data I collected with instrumentation here in Nevada, starting a week after the accidents in Japan. I was not yet born when previous events released large quantities of radionuclides into the environment (Atmospheric Nuclear Testing, Chernobyl, etc.), and so the Fukushima accident represented a situation in which I could put my skills into action collecting environmental samples. Today, these low concentrations of short lived isotopes attributable to Fukushima are no longer detectable in the local environment here in the US, however significant amounts of soluble Cesium-134/137 was deposited in the prefectures surrounding the Fukushima Daiichi Nuclear Power Plant as well as in the Pacific Ocean in the vicinity of the plant. The US and Japanese government as well as independent groups have published maps of this deposition on land, and this data should be used going forward to focus decontamination efforts and inform and update closure areas.
I am interesting performing additional analysis of environmental samples from Japan and the areas surround the crippled reactors, so please send me a note if you would like to provide samples for the effort. They will need to be sterilized (standard kitchen ovens can accomplish this) prior to their shipment to the US to comply with USDA regulations.