The design of the Fukushima reactors (currently experiencing some…er…problems due to the combined effects of the earthquake and tsunami) is detailed in this helpful backgrounder from the NRC: Boiling Water Reactor (BWR) Systems [pdf]
I knew a good bit of the science of what went on inside the different types of nuclear reactors, but this document provides a good bit of hardware insight (to an engineer at least) of how the containment and emergency systems are designed.
For comparison, here is the backgrounder on Pressurized Water Reactors (PWR), which the larger part of our 104 active nuclear power plants use.