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Three Mile Island expert: Fukushima could kill 200,000

Interview: The worst is "probably" past, but there’s a one-in-four chance Fukushima could deteriorate. Here’s how.

It’s a 7 now. If you’re asking, does it have the potential to get worse? The answer is yes. Let me explain the biggest risks for the future.

In unit 1, there’s so much mud in the reactor that they can’t get water into the core, which they would normally need to do to prevent it from overheating and melting down. Instead, it appears that they are flooding it from the outside, and cooling it that way.

That’s working, except that the containment structure on unit 1 was not designed to handle all the excess weight from the water. If there’s an earthquake — not a magnitude 9 on the Richter scale, like the one that kicked off the accident, but one just over 7 — the containment could fail.

If that happens, unit 1 could become a Chernobyl on its own.

But my biggest fear right now is the unit 4 spent fuel pool — the area outside the containment where they store the degraded but still-radioactive fuel that they’re no longer using to power the reactor. That worries me a lot.

There was a report this week that they found iodine-131 in that fuel pool. Iodine-131 can only come from nuclear fission, and because it has a short life, it disappears after about 80 days.

In other words, the presence of iodine-131 suggests that the spent fuel has started its own chain reaction without any human intervention.

That tells me that the racks that have been distorted — by the earthquake, or by the crane that fell in, or by the heat that caused the first explosion.

You’re talking about the racks in the fuel pool that keep the spent fuel apart, preventing the chain reaction that normally goes on in the reactor. And you’re saying that these racks were apparently damaged, enabling the fuel to reach critical mass and re-start the chain reaction on their own, without controls?

Yes. As workers pour water into unit 4 — which they need to do to keep it cool — they might essentially be creating a nuclear reactor, without control rods used to shut down the reaction, and without a containment building to keep the radiation in.

So unit 4 is still a significant risk. The fuel could get hot enough from the chain reaction that it will boil the water out again. So we could still get a fuel pool fire. That would volatilize some really heavy elements, sending some highly carcinogenic materials into the atmosphere. This should be a very big concern.

And that’s not the only problem. Another concern is that as a result of the accident, the building housing unit 4 is very weak structurally. They’re going to have to shore it up somehow from below so it can handle all the extra weight. Right now there’s little or no water in the fuel pool. They need to add water to keep the fuel cool. The pool has a crack in it, so it’s not clear that they can fill it with water. If they do, they will add so much weight that if there’s another seismic event it could cause the building to break, which would not be good.

How likely is it that the accident will get worse?

My read is that the accident could get worse if an earthquake impacts unit 1, or if unit 4’s spent fuel starts a nuclear reaction without any human intervention. Both of those are maybe a 10 or 20 percent probability.

So there’s about a 70 percent chance that the worst is behind us, and a 30 percent chance that things could still get worse.

There are a lot of balls in the air. As Dave Lochbaum from the Union of Concerned Scientists says, "Even the best juggler in the world can have too many balls in the air. They have a lot of critical things in the air, and one wrong move could make the situation much, much worse."

What about the risks to units 2 and 3?

In unit 2, they’re pouring water in the top to cool the fuel. Nuclear reactors are usually cooled using a closed system, in which cooling water circulates through the fuel rods. When the water gets hot, it is cooled via a heat exchanger and re-used in the reactor. Because it never leaves the reactor the radiation stays inside.

But the water they’re pouring into the top of unit 2 is flowing out the bottom because the containment is leaking. So unit 2 is the biggest polluter of the Pacific. It’s going to constantly pour out water at a terrible level but it’s stable. I don’t think it’s going to get worse.

What about unit 3?

Unit 3 is the one that looks the worst, with the most rubble. But the reactor is actually the closest to being cool. It’s almost at boiling, 200 degrees Fahrenheit cooler than any of the other units.

That said, the spent fuel pool on unit 3 looks from all the pictures to be partially obliterated. And it’s the most highly contaminated because of the explosion. The damage to this facility tells me that the fuel has been scattered, and will be hard to reconstitute.

Do you think TEPCO and the Japanese authorities are doing a good job handling the crisis, and communicating the risks?

No. I think they’re doing a better job now than they were at first. But I don’t think they’re doing a good job. Part of the problem for at least the first three weeks was that the data was so poor. You can’t make good decisions based on bad data. I think that affected some decisions that were made poorly.

Things are better now as far as getting control, but I don’t think they’re really conveying the risks to the public.

Let's talk about the impact on people. What does this mean for Japan? When will people be able to go back to their homes?

Within six miles, I don’t think they’re going back within a generation. There will be so much contamination and it will take too long to clean. They’ve already found plutonium in the form of fuel rods off of the nuclear plant site.

There are also indications that some areas 25 miles away have cesium concentrations higher than Chernobyl. You’re going to be monitoring dairy and beef cattle for years.

How will this affect the ocean? And how will it affect fish?