The following is a rush transcript of the March 13, 2010, edition of "Fox News Sunday With Chris Wallace." This copy may not be in its final form and may be updated.

CHRIS WALLACE, ANCHOR: I'm Chris Wallace. And this is "Fox News Sunday."

Japan is rocked by a huge earthquake, and then a devastating tsunami that killed hundreds and damaged two nuclear plants. We'll have the latest from Japan and talk with a nuclear safety expert.

Then, Congress deadlocks over the budget as gas prices climb. We'll discuss both with the Senate top Republican, Mitch McConnell.

Two budget hawks sell a bipartisan plan to cut the deficit. We'll sit down with Senators Mark Warner and Saxby Chambliss.

Plus, the latest on Libya. What can and should President Obama do to oust Muammar Qaddafi? We'll ask our Sunday panel.

And our power player of the week: the undercover provocateur strikes again.

All right now on "Fox News Sunday."

And hello again, from Fox News in Washington.

Here is the latest on the situation in Japan:

Officials there now fear more than 10,000 people may have been killed in the earthquake and the tsunami. They are fighting partial meltdown at two nuclear reactors and more than 170,000 people have been evacuated from around the plants as a precaution.

For more, we turn to FOX News correspondent Greg Palkot who is in Shimada-shi, Japan -- Greg.

GREG PALKOT, FOX NEWS CORRESPONDENT: Chris, strong words from Japanese Prime Minister Naoto Kan calling tonight, the situation surrounding the earthquake and the tsunami that this country got hit with on Friday the worst crisis in Japanese history, calling on his country to face it with determination.

One part of that crisis -- the stricken nuclear power plant in the area of the natural disaster. Sea water had to be pumped in to the second reactor today to try to cool things down. Authorities say they have the situation under control. But the evacuation of citizens from the immediate area around the reactor continues, as does the screening for possible radiation poisoning. Dozens of people reportedly are testing positive for that.

This as the overall scope of the disaster becomes even more clear. We went up and down the coastline today and heard from people and saw as they try to put together the shattered bits of their lives. In fact, they also had to deal with some aftershocks, a big one felt by this crew this morning.

This also as help is on the way, including from the United States. The carrier USS Ronald Reagan off the coast of Japan may be reporting today that 20 helicopters brought aid from that ship, part of a multipronged effort, not just from the United States, but from the international community, to help Japan at this very troubled time -- Chris.

WALLACE: Greg Palkot reporting from Japan -- Greg, thanks for that.

Joining us now is Joe Cirincione, who is an expert on nuclear issues.

Mr. Cirincione, Japanese officials are now talking about fighting two partial meltdowns in nuclear reactors. Briefly, what's going on and potentially how dangerous?

JOE CIRINCIONE, NUCLEAR SECURITY EXPERT: This is an unprecedented crisis. It is extremely serious. One of the reactors has had half the core exposed already. This is the one they're flooding with sea water in a desperate effort to prevent it from a complete meltdown.

They also have lost control of a second reactor next to it. It is a partial meltdown. And there is actually a third reactor at a related site, about 20 kilometers away, that they have also lost control over.

So, you have multiple reactor crises at the same time. We've never had a situation like this before.

WALLACE: And what does it mean if you have a meltdown of the nuclear core?

CIRINCIONE: The worst case scenario is that the fuel rods fused together -- the temperatures get so hot that they melt together in a radioactive molten mass that bursts through the containment mechanisms and is exposed to the outside. So, it spews radioactivity in the ground, into the air, into water. Some of the radioactivity could carry in the atmosphere to the West Coast of the United States.

WALLACE: Really? I mean, thousands of miles across the Pacific?

CIRINCIONE: Oh, absolutely. In Chernobyl, which happened 25 years ago, the radioactivity spread around the entire northern hemisphere. It depends how many of these cores melt down and how successful they are on containing it once the disaster happens.

WALLACE: Now, you talk about the possibility of a huge exposure. The Japanese officials so far have evacuated people 12 miles from these plants. Is that far enough?

CIRINCIONE: Not under a meltdown scenario. And you've seen these evacuation radiuses extend as the crisis has developed. First it was two, and then it was six, now, it's 12.

We're told by reporters on the ground that, actually, 50 kilometers out they're being blocked from access. So, the effective evacuation area is actually larger than the official one that's been declared.

WALLACE: Put this in context: Japanese officials had been rating this as a four on a scale that I didn't know existed of one to seven for nuclear events. How does the situation in Japanese as it now stands compare to Three Mile Island in this country in 1979 and Chernobyl, that you mentioned, in Russia in 1986?

CIRINCIONE: If it were to stop right now, five might be a fair characterization of this -- a local event without significant injury. If it continues, it will certainly get to five, which is the Three Mile Island category of a serious event.

We almost lost Three Mile Island and almost went meltdown. It stopped at the last minute. That is the situation we're fighting to maintain in Japan.

If there is a meltdown, that puts in a six, even a seven, that's a Chernobyl category -- a serious nuclear incident with potential for large scale loss of life.

WALLACE: So, what are we talking about, 12 hours, 24, 48 hours? And what are the keys as to whether this becomes a serious accident or a catastrophe?

CIRINCIONE: We're in a key period now. So, the next 12 to 24 hours will tell us whether the Japanese officials will able to get control back over these reactors, or it's gone, it's lost. The pumping of the sea water into reactor number one is that last ditch effort to try to stop it before it's too late. If they can succeed, if they can hold it for the next 24 hours or, so then these reactor cores will cool down and will be implied path to containing this disaster.

WALLACE: Mr. Cirincione, we're going to have to leave it there. We want to thank you so much for coming in and helping to shed light -- help us understand what's happening in Japan right now. Thank you, sir.

CIRINCIONE: Thank you, Chris.

WALLACE: Joining us now from his home state of Kentucky is the Senate's top Republican, Mitch McConnell.