When you hear about "meltdowns" and "hydrogen explosions" and damage to the buildings housing nuclear reactors, it's hard to the layman to know exactly what's going on and what the dangers are.
I found this blog post to be a very long, but very informative read on the topic. It was written two days ago, before an additional hydrogen explosion, but it does explain why such explosions are not necessarily to be feared. So far, despite just about every imaginable thing going wrong, beginning with an earthquake seven times as powerful as what the reactor was built to withstand, this decades-old reactor is performing just as it should -- so far, anyway.
This is in sharp contrast to Chernobyl, where poorly designed equipment and bad management led to the equivalent of a massive dirty bomb being unleashed on the general public.