Updated

This is a rush transcript from "On the Record," March 11, 2011. This copy may not be in its final form and may be updated.

GRETA VAN SUSTEREN, FOX NEWS HOST: This is a "Fox News Alert." Japan is rushing to prevent a nuclear meltdown. Now, that massive quake is now threatening to cause a possible nuclear meltdown at a power plant located in northeast Tokyo -- northeast of Tokyo. The earthquake caused the power plant's cooling system to malfunction, causing radiation levels to skyrocket to about 1,000 times above normal. The Japan nuclear plant is in a state of emergency. Now, in total, five reactors within two plants have been declared a state of emergency. Thousands of people have now been told to get out, to evacuate.

Joining us is James Acton, a physicist who examined a Japanese nuclear plant that spilled radioactive material after an earthquake in 2007. He's also associated with the nuclear policy program at the Carnegie Endowment. Nice to see you. All right, how serious is this?

JAMES ACTON, NUCLEAR PHYSICIST: Well, you know, any time you have a release of radiation into the environment, it's serious. But if this accident doesn't get any worse, then there's not likely to be significant damage to people or to the environment. If, however, they can't get the cooling system up and running and the fuel starts to melt, then you could have a very significant release of radiation. And then we could be -- and then we could have a major nuclear accident on our hands.

VAN SUSTEREN: Well, the thing that's distressing is that it's -- it didn't cool down like it should. Then there was a redundancy, a back-up cooling system. That has failed. And so what is -- what -- what is next to try to cool this down?

ACTON: Well, you know, part of the issue is, we don't actually necessarily know what the problem is right now.

VAN SUSTEREN: They don't or we don't?

ACTON: We don't.

VAN SUSTEREN: OK. All right.

ACTON: I'm hoping -- I'm hoping -- I'm hoping that they know what...

(CROSSTALK)

ACTON: You know, when the earthquake hit, the reactor initially did what it ought to do. It scrammed, which means it shut itself down. But there's a large amount of radioactivity in the core, and that still produces a lot of heat even after the reactor has been shut down. And you need to be cooling that. And to drive the pumps that pump the water, you need electricity.

And there appeared to be a series of accidents. So firstly, because of the earthquake, the external power lines got knocked out. Then the on- site diesel generators, for reasons that I don't know we understand, stopped working.

VAN SUSTEREN: Those are both very bad signs.

ACTON: It's a very bad sign.

VAN SUSTEREN: OK.

ACTON: And that only left the batteries on site, and we're not sure how many batteries there are and exactly what the state of them is. So if the problem is only a lack of power, then they have to get some form of power back into the plant to drive the pumps to cool it down.

VAN SUSTEREN: If those batteries aren't working, then what?

ACTON: Well, if they can't restore power or if there's actually damage to the cooling systems -- and as I emphasize, you know, we don't actually know what the problem is -- then the temperature in the reactor is going to start to rise.

And eventually the metal outside bits of the fuel are going to start to melt, and that's going to expose the radioactive fuel pellets to the water inside the reactor. And when that happens, then the water that gets turned into steam that's now being vented into the environment, rather than being very slightly radioactive, could become highly radioactive. And that -- this is the worst-case scenario. I mean, I want to emphasize that we're not there yet. There's a range of possible outcomes to this crisis.

VAN SUSTEREN: All right, you use the term "eventually." What's "eventually" mean? What's the -- what's the time on this?

ACTON: Well, you know, it could be anywhere from hours to days. There's a lot of unknowns in this. We don't know what the problem is. We don't know what the state of the core is at the moment. So it's very, very hard to put a specific time on this, but this could be anywhere from hours to days.

You know, in the case of the Three Mile Island accident, the crisis actually kind of unfolded over the course of two or three days. Now, the causes of the accident of Three Mile Island and the Fukushima accident are quite different, but the result, which is a problem of trying to cool the core, is actually relatively similar.

VAN SUSTEREN: You said that the website was being updated, talking about -- you know -- and it -- when did it -- and you told me then they've stopped updating the website. Now, not to be a conspiracy person, but I mean, like, why -- I'm a little bit curious why they're not updating the status on the repair of this.

ACTON: Well, we don't know. I mean -- I mean, you know, I think the most likely explanation is that the company is trying to deal with, you know, a reactor accident, and the people who are running the company think they have bigger priorities than updating the website.

VAN SUSTEREN: And I hope that's exactly the reason.

ACTON: But you know, it's -- it's -- it's part of what makes this so hard to commentate on is there's so much we don't know about what's going on at the moment. But I mean, I think -- I think -- you know, I mean, I think the bottom line is that if they stabilize the reactor as it is and there is a slightly radioactive steam being let out, then there's not going to be very much damage, if any. If there's a reactor melt, then -- then, you know, we're -- we potentially have one of the two or three most serious nuclear accidents in history on our hands.

VAN SUSTEREN: James, thank you.

ACTON: Thank you very much.