A statistical inevitability.
Some nuclear power plants are built on fault lines, but every mine, dam, oil rig, and waste dump is founded upon a tacit acceptance of the worst-case scenario. On a long enough timeline, everything that can go wrong will, however small the likelihood is from one day to the next. The responsible parties may wring their hands about the Fukushima meltdown—and the Gulf of Mexico oil spill and the Exxon Valdez and Hurricane Katrina and Chernobyl, Bhopal, Haiti—but accident is no accident.