Nuclear power is an opaque, technologically complex, and—let's be forthright—potentially hazardous way to generate electricity. Because of these characteristics, some people will always view the technology with skepticism or suspicion and argue that the benefits are not worth the risks. In addition, in part because nuclear power presents many potential benefits, there will always be others, usually with more thorough technical expertise, who see it as an obviously elegant solution to major energy and climate constraints and whose risks are relatively small and manageable. These well-worn and arguably defensible perspectives have infused and colored the past few decades of public policy discourse—particularly in the US and some European countries—on nuclear power as part of global energy supply. The pressing constraints of anthropogenic climate change, regional air quality in growing cities, and volatile resource prices, however, raise the appropriate question of how much nuclear power might reasonably contribute in a future global energy portfolio.