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Ice Wall May Stop Radioactive Leak At Japanese Nuclear Plant


Earlier this week, workers in Japan began construction of an underground ice wall around the melted-down nuclear reactors at Fukushima. It is hard to even say that sentence without feeling like you're relating some science fiction tale. But it's true. The ice wall is designed to stop hundreds of tons of radioactive groundwater from leaking into the nearby Pacific Ocean. NPR's Geoff Brumfiel has been covering this story for a long time. Welcome back to the program.

GEOFF BRUMFIEL, BYLINE: Thank you, nice to be here.

INSKEEP: Why an ice wall?

BRUMFIEL: Well, basically the idea is that you have to stop water from leaking out of the bottom of Fukushima. And you don't have that many options. So one of the things they've come up with is this sort of crazy idea of an ice wall. Basically, it works like this. When the soil is moist, it's obviously possible to freeze it. So you go around, you drill holes about every three feet for a mile around the plant. You put in the pipes. You actually run saltwater, which freezes at a lower temperature than fresh water. That causes the soil to freeze and slowly you can build up an impermeable wall, several feet thick. When water comes to the wall, it freezes - and so that's how this ice wall's created and that's how it stops water.

INSKEEP: So you're building this giant refrigerator, this giant freezer, basically...

BRUMFIEL: That's right.

INSKEEP: ...To freeze the ground. But why ice? Is that an impermeable substance, assuming it stays very cold?

BRUMFIEL: Yes, actually it is because, as I said, so you have - when groundwater comes to the wall, that water will freeze. It will become ice, as well. And so you have this sort of self-building wall. Now why do that as opposed to putting metal into the ground, like steel plates? They're trying that, too, actually. The reason is that you need something very thick, very big and that can run for miles around the plant. It's just not realistic to try and put in metal that could degrade over time. You know, the best thing to do is try to use the environment itself. This is a technique, incidentally, that's used in construction for tunnels, for trying to dig foundations in very moist areas, like ports. It does work.

INSKEEP: So the craziest sounding solution is actually the most practical. But why is it still necessary? Why is this reactor still leaking?

BRUMFIEL: Well, that's really an interesting issue. I mean, the problem with the reactors is that they still have hot nuclear fuel inside. And so workers still have to put water into them to keep them cool. But, you may remember, the reactors were heavily damaged by an earthquake and tsunami. And, the fact is, they leak, so water's actually leaking into the basements. And groundwater, then, is coming in because the reactors are between the Pacific Ocean and the mountains. It's flowing into the basements, mixing with the very radioactive water. This happens to hundreds of tons of water a day.

INSKEEP: So how much does it cost to surround an entire nuclear reactor with a ice wall?

BRUMFIEL: Incredibly, you can do it for under half a billion dollars.

INSKEEP: (Laughing) Cheap then, I suppose. Geoff, thanks very much.

BRUMFIEL: Yeah, no problem.

INSKEEP: NPR's Geoff Brumfiel. Transcript provided by NPR, Copyright NPR.

Geoff Brumfiel works as a senior editor and correspondent on NPR's science desk. His editing duties include science and space, while his reporting focuses on the intersection of science and national security.
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