Click on the chart for a bigger version. Image: Randall Munroe, XKCD, CC
Putting Radiation Exposure in PerspectiveRandall Munroe, of XKCD geek-fame, along with a senior reactor operator at the Reed Research Reactor, has created a chart that puts radiation exposure in perspective.It goes from ridiculously small exposure (so small that any effect it could have is totally lost in the background radiation levels of Earth, where you are exposed to more or less radiation depending on where you live) all the way up to spending 10 minutes next to Chernobyl after the explosion and meltdown. Interestingly, the maximum external dose from the "Three Miles Island accident" is about 1/3 of a mammogram, and much smaller than the yearly dose permitted for nuclear workers. The most important question over the next few weeks will be: What level of radiation did the Japanese workers that stayed behind at the Fukushima plant get exposed to? Via XKCD, sources of the radiation chart.
See also: Japan Nuclear Crisis: External Power Reconnected at Fukushima 1 (March 23rd, 2011)