The nuclear disaster at Fukushima, Japan is continuing to deteriorate. Multiple explosions have blown roofs and outer walls off reactor buildings, and a dire struggle is under way to prevent the worst.

For several days, authorities have attempted to reassure the public. Now, they are pleading for help.

To get independent answers about the risks faced by people, GlobalPost turned to Arnold Gundersen, a 39-year veteran of the nuclear industry. Now chief engineer at Fairwinds Associates, he has worked as a nuclear plant operator and he served as an expert witness in the investigation into the Three Mile Island accident.

GlobalPost: Officials have said the possibility of a large-scale radiation release is small. Do you agree?

Arnold Gundersen: I think that the probability of a large scale release is about 50-50, and I don’t call that small.

GlobalPost: Why do you think that?

Gundersen: For several reasons. One, you’ve got three reactors involved. Two, you’re already picking up radiation on aircraft carriers a hundred miles away at sea, on helicopters 60 miles to the north, and in town. So clearly, as these plants become more and more difficult to control, it becomes quite likely that a containment now will have a gross failure. And a gross failure will release enormous amounts of radiation quickly.

GlobalPost: The New York Times is reporting that radioactive releases could go on for weeks or months. How concerned should we be about that? At what point does a reactor like this becomes less menacing?

Gundersen: The chain reaction has stopped. That happened in two seconds. But the radioactive isotopes are still decaying away. They’ll decay for at least a year. So you have to release the pressure from that containment pretty much every day. With releasing the pressure will come releasing radioactive isotopes as well.

So yes, the Times is right that every plant — there are now three or four of them — will be opening up valves every day to make sure the pressure is down. And there will be releases from these plants for at least a year.

GlobalPost: How much of a health threat is that?

Gundersen: Within 90 days, the iodine health risks will disappear, because that will decay away. But the nasty isotopes — the cesium and strontium will remain for 30 years. And they’re volatile.

After Three Mile Island, strontium was detected 150 miles away from the reactor. That ends up in cow’s milk and doesn’t go away for 300 years. The releases from these plants will last for a year, and will contain elements that will remain in the environment for 300 years, even in the best case.

If we have a meltdown, it will be even worse than that.

GlobalPost: The ultimate risk in any nuclear accident is that the heat can grow so intense that the steel containment vessel is ruptured, releasing a large amount of radiation. You say there’s a 50-50 chance of this happening. What kind of health effects can we expect?

Gundersen: First, it’s important to know that this steel containment is about an inch thick. It’s not some massive battleship of steel. The reactor is already open, because the pressure relief valves have to stay open.

On top of that, these containments have already breached. We saw iodine and cesium in the environment before the first unit exploded. When you see that, that’s clearly an indication that the containment has breached.

Now, is it leaking 1 percent a day? Probably. Is it leaking 100 percent a day? No. I think for the neighboring towns out to 2 miles, they won’t have anybody back in them for five years. Out to 15 miles, I doubt you’re going to see anyone back for six months. And that’s in the best case, without a meltdown.

If we have a meltdown, I don’t think anyone will be back within 20 miles for 10 or 15 years.

GlobalPost: What would happen if they did return?

Gundersen: There would be higher incidence of cancer. The groundwater would be contaminated. With a meltdown, you’re worried about surface contamination of everything within miles of the plant, and groundwater contamination as well.

GlobalPost: How far would the ground water contamination spread?

Gundersen: Chernobyl had a meltdown, and that groundwater wedge is gradually working its way toward Kiev, which is a very large city [about 80 miles away]. That groundwater contamination lingers for 300 years. It’s not something that’s easy to mitigate.

GlobalPost: That’s a serious issue in a country like Japan with a large population and a small land area.

Gundersen: That’s right.

GlobalPost: You mentioned that the containment vessels have already been damaged. It appears that officials are reporting the opposite. How do you know you’re right?

Gundersen: We’re seeing iodine and cesium in the environment. That’s an indication that the containments are leaking. Exactly how much they’re leaking it’s hard to say.

I can’t understand how officials can say that the releases are low, when they don’t have any instruments that are working. Their batteries have failed, and when the batteries fail, all of the instruments stop working. So it’s hard to determine what the radiation levels are, and what the pressure levels are.

The Japanese and the nuclear industry are heavily, heavily financially invested in this. My experience is that, after Three Mile Island and after Chernobyl, everybody said there wasn’t a problem, until there was a problem. So I really don’t put much faith in official pronouncements the first week of an accident.

GlobalPost: So the people who have access to information have a self interest in making that information look as benign as possible?

Gundersen: Yes. On top of that, the officials don’t want to provoke a panic. So there’s a financial long term interest to try to minimize the impact. The flip side of that is that in the process you lose transparency. There is no transparency right now. We’re dealing with second hand information.

I understand from one source that the second unit cannot be vented, because the vent is jammed. I don’t know if that’s true or not. I have one source, and I like to have two. But this accident hasn’t played out yet. It could clearly get worse before it gets better.

GlobalPost: When you say the venting system is jammed, does that mean that pressure will keep building up until something catastrophic happens?

Gundersen: Yes.

GlobalPost: That sounds bad. There have been explosions at two of the buildings where the reactors are housed. You used to operate nuclear reactors. Would the control rooms be affected by these explosions? And how do they continue controlling the reactors under these circumstances?

Gundersen: Yes. The control rooms have become almost uninhabitable. The operators would have to be in Scott air packs, because the ventilation failed. Otherwise they would be breathing contaminated air. The control room is very close to these reactors. Probably 200 feet away. I doubt there’s much being done in the control rooms. They’re contaminated, and the air is unfit to breathe. It’s very difficult to get anything done if you’re wearing an air pack and a bubble suit.

GlobalPost: So how do they release the pressure? Are they sending people to the reactor to manually do these things?

Gundersen: They’ll send someone out to manually open a valve. And then that person will go back out to manually close a valve. In a high radiation field, there are only so many trips you can make before you’ve exceeded what they call emergency limits. So these people are picking up very large doses in very short periods of time. For their personal health, you can’t send them out again.

So they’re running through the available number of operators to do these high risk maneuvers.

GlobalPost: Is it highly skilled work?

Gundersen: Yes.

GlobalPost: Do these doses endanger their health, or are they below thresholds that would cause a problem?

The probability of these workers getting cancer is dramatically increasing, because the doses they receive in a day are higher than what they get in a year. For every 250 rem received, there will be a cancer. That’s pretty well defined. So if one person picks up 2.5 rem, for every hundred people, one of them will get a cancer. That’s just a statistical crapshoot.

GlobalPost: How safe is Tokyo at this point?

The radiation is being diluted by the wind and spread out. Tokyo is a long way away. Germany is a long way from Chernobyl, and the ground in Germany is so contaminated that they are still prohibiting the hunting of wild boars, 25 years later.

But we don’t have a lot of accurate measures. There’s a U.S. aircraft carrier 100 miles away, and the workers on that aircraft carrier received in one hour the dose they would normally get in one month.

GlobalPost: Is there any risk that the radiation would reach American shores?

Oh it will. Chernobyl reached the U.S. The question is how much radiation? There’s not a lot of data to make that determination right now.

GlobalPost: Should people be concerned about food contamination?

Certainly in Japan they should.

I’ve gone out and bought potassium iodine pills, and I plan to take potassium iodine starting in about 10 days, just because I’m concerned about food contamination. That’s a personal choice right now. My experience says that it would be prudent to get potassium iodine pills and take them, to avoid any of the iodine that might come over. But there’s not a lot of data to support whether or not potassium iodine really helps.

GlobalPost: Is that something that you can buy in a health food store?

Yes, you can get these pills in health food stores and online, although I hear that they’re selling out.

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