When we design machinery that is dangerous and prone to failure we try to reduce risks by tight regulations, specifics, and centralised control. Of course, these strategies are expensive and therefore are best implemented over large scales. So, we are raising the stakes by building bigger and more expensive systems in order to hedge the risk of failure. In the case of nuclear energy, the result is the concentration of power production in large plants. That strategy seems to work, within limits: on the average, the safety record of the nuclear industry is not bad. But when something goes wrong with a nuclear plant, it tends to go wrong in a big way, such as with Chernobyl and Fukushima.