The whole thing is just a ticking time bomb...I can't help but think that they Japanese can just stall it so everyone around the area to get out...
<facepalm> It's not a bomb... A meltdown is NOT a nuclear explosion, and has nothing to do with explosions.
A meltdown is when the rods that house the pellets literally melt. Hence the name. And then the radioactive pellets are then exposed. The reason they're worried about this is because the outer casing that surrounded the rods blew from the buildup of steam that resulted from the water in the coolant system evaporating and having nowhere to go (there's no power there, so the steam couldn't be processed and re-cooled back into water, which is what keeps the water flowing and cooling the rods; no water = no cooling of the rods). This is why they're dumping seawater on the rods to try and cool them. But there are still alot of things that have to go wrong for this to be another Chernobyl.
Here's how it works. You've basically got 4 layers of protection, or lines of defense. And yes, this is from the physicist's website. As I said, I didn't go to college to study this stuff, so I'm simply relaying the information. And this is really just a bare bones version of it.
The first 'layer' is, obviously, the rods. They house the pellets. But because these pellets are radioactive, the rods get really hot really fast (radiation tends to heat things up). So you need a second 'layer to prevent them from melting.
The second layer is a tank or containment unit of some kind that's filled with water. The tank has a processing mechanism that pumps out steam, because the water will boil after awhile (similar to how water boils on a heated stove). Problem is, there's still radiation, so you need a third layer.
The third layer is a cement container. Now, I admit, I'm not exactly sure how to explain this one, but it keeps the lion's share of the radiation contained, regardless of what happens to the rods.
Finally, you've got the shield itself, which you can see from the outside (it's those block-looking things you've been seeing on the news). This contains whatever radiation the other three layers don't contain.
So, what's gone wrong so far? Well, the steam or hydrogen explosion happened, because of the fact that there's no electricity to pump the steam itself to be cooled and turned back to water. So, the shield is gone. Now you've got the steam escaping, causing the rods to be exposed (and yes, there's going to be some radiation; I'm not saying there isn't). They're dropping seawater onto the rods to prevent a meltdown (presumably, through the hole the steam normally escapes from), hence the steam that we see coming from the pools. So in other words, the rods are only exposed for short periods of time. The main thing that should be a concern right now is that Japan said one of the reactors has a cracked or damaged containment vessel (the cement casing) from one of the more recent 'explosions' (I think there's been four now, but we'll probably see see two more, because there are six total). That could potentially cause a stronger buildup of radiation from that particular reactor.
The initial 'explosion' was not a nuclear explosion. It was caused by the steam building up. The only danger here is the radiation itself, not an explosion (and yes, radiation is just as dangerous as it was in the days before Captain Planet made us think we could all be near a radioactive supervillain without getting radiation sickness). I'm not saying there isn't danger here. But people, especially the media, are taking it out of context without knowing the facts behind how a nuclear reactor works and what a nuclear meltdown is. I've only recently learned what it really means.
Not to mention, I think the real disaster here is the thousands of people that died from the tsunami itself and millions that were affected, not a radiation leak that probably won't kill anyone. Yes, it deserves coverage. But this is just way too much coverage, when you've got millions of people affected by the quake and tsunami itself that deserve the coverage more.