When officials decided to vent radioactive steam from one of the damaged nuclear power plants in Japan, they knew it could result in a hydrogen explosion. And, even though an explosion is exactly what happened, the decision was still the best option for avoiding a total meltdown, the AP reports in an interesting piece that traces the chain of events from Friday, when the earthquake damaged the Fukushima Dai-ichi nuclear complex, to this morning, when a total of six reactors were placed under a state of emergency. More from Japan: