AUDIE CORNISH, HOST:
The U.S. believes North Korea is making nuclear warheads that are small enough to sit on top of a missile. This is according to a new report today from The Washington Post. As the news broke, President Trump ratcheted up his rhetoric.
(SOUNDBITE OF ARCHIVED RECORDING)
PRESIDENT DONALD TRUMP: North Korea best not make any more threats to the United States. They will be met with fire and fury like the world has never seen.
CORNISH: Joining us to discuss these developments is NPR science correspondent Geoff Brumfiel. Welcome to the studio.
GEOFF BRUMFIEL, BYLINE: Hi, Audie.
CORNISH: So what have you been able to find out so far about this reporting?
BRUMFIEL: Well, the first thing to say is that NPR hasn't been able to confirm these reports. Multiple intelligence agencies have so far declined to comment. But according to The Washington Post, the Defense Intelligence Agency has an assessment that says North Korea can produce nuclear weapons that are small enough to fit on top of its ballistic missiles. Now, North Korea just conducted two ballistic missile tests in July - intercontinental ballistic missile tests. The second one had a range that could reach targets in the Lower 48. So if true, it's a big deal.
CORNISH: Now, what would North Korea have to do to accomplish this?
BRUMFIEL: Well, a nuclear weapon is basically a runaway nuclear chain reaction. It's almost like a little meltdown. But to make it happen, you have to have a lot of conventional explosives that trigger the blast. That makes primitive nuclear weapons very heavy because you have to pack all this stuff around the nuclear material.
There are ways to trim back. You can use less high-explosive. You can use it in special ways. You can use less nuclear material. And all that makes you able to make a smaller, lighter bomb. That of course matters a lot when you have a missile because the smaller and lighter something is, the further your missile can take it.
CORNISH: So what's the evidence so far that this has actually happened?
BRUMFIEL: Well, the first piece of evidence we have is that North Korea sent us a picture. Back in 2016, Kim Jong Un was photographed in front of what was being called the disco ball of death by some analysts. It's this giant, round, metal ball. It actually looks like a model of a miniature nuclear device. Now, I say a model because, A, Kim Jong Un probably wouldn't pose in front of a live nuclear weapon. But also, North Korea has a habit of publicizing models. In parades, they've shown fake missiles in the past. So that's not the best piece of evidence.
The best piece of evidence we have are the nuclear tests. They've done five nuclear tests now. And other countries have been able to miniaturize in fewer tests. So it seems reasonable to assume that they might have been able to miniaturize by this point.
CORNISH: At the same time, this is essentially leaked intelligence. No names are attached to it. Some people are saying, look; remembering back to the Iraq war about claims of weapons of mass destruction. Not to draw a parallel there, but how should we be looking at these claims about North Korea?
BRUMFIEL: Yeah. I mean I think there's an important difference here, and that's there's hard data. Each nuclear test has been picked up by an international monitoring network of seismic stations all over the world. The missile tests have been tracked not just by the U.S. but by the radars of our allies in South Korea and Japan. There is a lot of consensus in the international intelligence community right now about what North Korea can do. These missiles are real. These nukes are real. I think there's some room for argument about how exactly operationally it could all work. But there's definitely a lot of progress. I think everyone in the world right now pretty much agrees on that.
CORNISH: But is there a sense of what North Korea really wants out of all this?
BRUMFIEL: Well, no one can read the mind of Kim Jong Un. But I think, you know, what they're looking for is nuclear deterrence. And what that means is that they have a system of missiles and warheads that mean that if the U.S. or anyone else tried to attack them, they could hit back, that they could hold targets in the U.S. at risk. Now, do they want something more? Do they - what will they do when they get that capability? I mean these are all open questions, and it's, you know, really speculation as to what nuclear deterrence means in the north.
CORNISH: That's NPR science editor Geoff Brumfiel. Geoff, thank you.
BRUMFIEL: Thank you, Audie. Transcript provided by NPR, Copyright NPR.
