GUY RAZ, host:
And of course, as we just mentioned, all eyes are on that nuclear power plant in Fukushima, about 170 miles northeast of Tokyo. An explosion there earlier today destroyed at least one building. Teams of engineers are scrambling to prevent a meltdown at one of its reactors.
NPR's science correspondent Christopher Joyce is following that story.
And, Chris, explain, first of all, what happened to that reactor. And what's the current status there?
CHRISTOPHER JOYCE: Well, the first thing that happened was that it lost its outside power, its AC power. It went to backup diesel. Then it lost the backup diesel. Nobody knows exactly why. Then, apparently, they went to batteries.
What they're doing now is they're trying very hard to get electrical power back. It's really key because you need electricity to run the water through the reactor vessel. That's what cools the uranium fuel rods. And apparently, they haven't been able to keep them cool enough because they had an explosion, and that's probably from hydrogen. What happens is it builds up. When you overheat the water, the hydrogen is split off from the oxygen, H2O, is what water is. And the hydrogen split off and it's very explosive. That's the consensus now.
Radiation is, at this point, there's some radiation escaping according to authorities. They don't think it's directly from the reactor vessel, which is what holds the fuel, but they think it's from the cooling water that's come in contact with the fuel rods.
And, you know, the radiation so far is on site and it's not acute lethal levels, but it is of great concern. One thing that we have heard is that they think that they may have detected cesium-137. And this is a signature, it's kind of like a fingerprint. If you got a fuel rod that burns or breaks, you end up getting cesium-137, and that's not a good sign.
RAZ: Now, apparently, Japanese authorities are saying that they're going to flood this reactor with seawater. First of all, why would they do that? And has that been done before?
JOYCE: The experts I've talked to say no. In fact, one call it a Hail Mary. It's kind of a last resort. Normally, they use fresh water. If you use seawater, you're going to corrode all the metal parts. You know, that's -you're saying, we're never going to recover any of this reactor. But seawater has the advantage of there's plenty of it.
And the problem might be that - if they can get it through the existing closed loop system for cooling, then, you know, it might be irradiated, but they can keep it. But on the other hand, they may just have to pump it back in the ocean after it goes through the reactor. In which case, it would be radioactive.
RAZ: And, Chris, there's also some talk of pouring boric acid into the reactor vessel. What does that do?
JOYCE: And maybe that sounds a little weird, but actually, you know, boron and boric acid will dampen the reaction. Boron absorbs neutrons. And it's neutrons that are firing around in that reactor vessel that are creating the nuclear fission, the nuclear reaction that causes the heat that makes the steam that makes electricity. So, boron presumably is another way of sort of cooling off the reactor.
RAZ: Chris, the big question, of course, is that if none of these works, what happens next? I mean, are we looking at a Three-Mile-Island-type meltdown here?
JOYCE: That's a possibility. People are speculating. Nobody knows where we are on that continuum, at the end of which lies Three Mile Island or worst. You know, in Three Mile Island, there was a partial meltdown; some of the fuel did melt, but they contained it. It didn't go outside the containment building. There is a containment building here as well. So, if there is a partial melt, maybe it might end up the same.
You know, the worst-case scenario, of course, will be something like Chernobyl, where there was a huge meltdown and lots of radiation released, and people are hoping that won't happen.
RAZ: That's NPR science correspondent Christopher Joyce.
Chris, thank you.
JOYCE: You're welcome. Transcript provided by NPR, Copyright NPR.