Media gave too dire picture of Fukushima nuclear plants
Media did not hesitate to use the words like disaster, catastrophe, apocalypse to sum up the situation at the nuclear power plants damaged by earthquake and tsunami. This was done without drawing their description from the most basic reator physics, causing fear, uncertainty, and recent market volatility. The following links lead to the science of basic safety features that are built into the reactor design. After reading them, I felt less dire about the situation at Fukushima.
Media always gives dire predictions. Ratings. That's why you don't see many happy stories on the news. If it bleeds it leads.
Some of the issue is just lack of information. There isn't a lot of precedent on these types of situations either. I feel bad for the people working there. I'd probably take a sick day. I know a lot of the responders at Chernobyl died rather painfully.
As to the market, it was correcting anyway. If it wasn't this fear, it would be turmoil in the mideast causing the market decline. If it wants to go down, any excuse will do.