Japanese Quake Threatens Nuclear Plant

Japan has declared an atomic power emergency after an earthquake led to damage at one of the nation's nuclear plants. The plant's cooling system became impaired after the plant lost its main power supply and a backup system failed to take over. Japanese authorities are releasing slightly radioactive vapor to ease pressure at the reactor as they work to restore full power. NPR's Jon Hamilton talks with host Melissa Block.

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MELISSA BLOCK, host:

Here's another problem created by the earthquake off Japan. A nuclear power plant is in trouble. Thousands of people have been evacuated from the area near a nuclear reactor on the coast, in Fukushima Prefecture. Its cooling system has been running on batteries. And if the system fails, the plant's radioactive core could melt down.

NPR's Jon Hamilton joins me now to talk about what Japan is facing.

And, Jon, they're calling - Japan is calling this an atomic power emergency.

JON HAMILTON: Right. Well, that's what they do when there's the potential for a release of radioactive material from a power plant. So far, it appears that there hasn't been any actual release. And it's worth noting that the nuclear power plants in Japan include a lot of safeguards. In this case, for instance, when the earthquake hit, the plant automatically shut down the nuclear reaction.

The thing is that you can't just switch off radioactivity. The reaction stops but there's a lot radioactive stuff that's left and its still producing heat. So this plant, which is a couple hundred miles north of Tokyo, this plant needs to keep its cooling system going for a couple of days. And that will give the core a chance to cool off.

BLOCK: Needs to keep the cooling system going. What makes that cooling system work?

HAMILTON: Well, in a word: electricity. The cooling system is really just water and it gets circulated around by electric pumps. And the earthquake knocked out the main source of power for those pumps. Fortunately, there is a backup system of diesel generators and that was supposed to kick in. Unfortunately it didn't work. So, you know, that could have been because the tsunami damaged the generators.

In any case, what's left is the final source of backup power and that's a bunch of batteries.

BLOCK: Batteries that give how much power in all?

HAMILTON: Kind of depends who you ask. I've heard everywhere between four and eight hours. Even assuming it is eight hours, if you do the math here, you know, you realize that the initial set of batteries is probably just about gone.

BLOCK: Well, that clock ticking then, Jon, what is the government in Japan trying to do?

HAMILTON: Several things. Obviously they're trying to restore the main power -that is actually just the electrical grid, which would get the generators working again. There are also reports that the U.S. and Japan have been working together to bring in another sources of power. And that could be new batteries. It could be new generators. It could be a way to repair the existing diesel generators.

Flying in generators, though, I should say, is a hard thing to do because they are really heavy. And so, your average helicopter is going to have trouble lifting them in.

BLOCK: And, Jon, if all of this fails what then?

HAMILTON: If it all fails, well, first the core of the reactor will start to heat up. There're some indications that may already be happening. And when the core heats up that turns the cooling water into steam and that builds up pressure in the system. You can ease that pressure if you vent some of the steam.

The problem is - and I understand that they may actually be thinking about doing this already, there's been some talk of that. The problem is that at this point, the steam is actually slightly radioactive, so it's not a great option. And also, when you release steam you are actually losing water from the system, and you need that water to keep the core from overheating.

So if the core gets enough - you run out of water, the core gets enough - it will actually melt. That's what happened, as some of us will recall the Three-Mile Island. And when the core melts it can release gases and particles that are highly radioactive. And those particles can get also caught up in steam that's released.

I should say nuclear plants are designed so that even when the core melts, all the radioactivity inside is supposed to stay inside what they call the containment structure.

BLOCK: Well, Jon, as you're talking to people about what's going on with this plant, are they envisioning a scenario like Three-Mile Island?

HAMILTON: So far, you're not hearing a lot of that kind of talk. Now, the Japanese officials are saying that they see very little chance of this being a Three-Mile Island-type event, certainly not Chernobyl.

On the other hand, it should be said that this is one of Japan's oldest nuclear plants. It was built way back in the '60s, started operating I think in 1971. And because it's so old that means it is probably more vulnerable to some kind of catastrophic failure.

BLOCK: And as we mentioned, they have evacuated thousands of people from this area.

HAMILTON: They have.

BLOCK: NPR's Jon Hamilton, thanks so much.

HAMILTON: Thank you.

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