ARI SHAPIRO, HOST:
Iran is now enriching uranium above limits set by the 2015 nuclear deal. That's the word from the International Atomic Energy Agency, which monitors Iran's nuclear facilities. Earlier today, Vice President Mike Pence offered this warning.
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VICE PRESIDENT MIKE PENCE: Under President Donald Trump, America will never allow Iran to obtain a nuclear weapon.
SHAPIRO: That's Pence speaking at a conference in Washington earlier today. And joining us now to discuss Iran's nuclear activities is NPR's Geoff Brumfiel, who covers science and security for us. Hey, Geoff.
GEOFF BRUMFIEL, BYLINE: Hi there.
SHAPIRO: Let's start with the vice president's comment there. Is that what Iran is trying to do - get a nuclear weapon?
BRUMFIEL: Well, at the moment it looks like the answer to that question is no. So you need a little enrichment 101 here. Buckle up.
BRUMFIEL: Only a tiny fraction of the uranium that gets dug out of the ground can actually be used for things like nuclear power reactors and nuclear weapons. And so what the process of enrichment is doing is actually concentrating that level. If you enrich to about 5%, that's good for a reactor. Closer to 90% is what you really need for a nuclear bomb. Now, under the nuclear deal, Iran promised to keep it pretty low, at 3.67%. Just over the weekend, Iran announced it was going to be going up to around 4 1/2%. That's still way below bomb-grade.
SHAPIRO: So if they're not sprinting in that direction towards a nuclear weapon, what are they actually doing?
BRUMFIEL: What they're doing is sending a message. The U.S. pulled out of this nuclear agreement last year, and they've been making Iran's life pretty miserable ever since. They've reimposed a ton of sanctions, and they've also imposed sanctions on anyone who does business with Iran.
But the U.S. isn't the only party to the nuclear deal. Europe, China and Russia were also supposed to provide Iran economic benefits. And so Iran is crossing these lines in the deal to really try and ramp up the pressure on those other parties to give them some sort of economic benefit to remain at the deal. And they've said that they're going to cross another line in 60 days if they don't start seeing those benefits, although it's unclear exactly what that line would be.
SHAPIRO: So some of this is signaling using uranium enrichment to send a message, but technically it does also get Iran closer to having what they need to build a nuclear weapon, right?
BRUMFIEL: It does. I mean, I would call it a baby step. Most of the experts I've spoken to about this were actually concerned. We knew Iran was going to make some sort of announcement. They were concerned that it might be Iran going all the way to 20% right away or near 20% enrichment. That would be a big step toward getting a nuclear weapon. So Iran is showing restraint here. They're clearly trying to slowly ratchet up the pressure.
SHAPIRO: So how would we know if Iran does decide to start racing toward a nuclear weapon? What signs would we see?
BRUMFIEL: Well, the enrichment levels could go up much, much higher. The other thing to watch for is right now there are all these nuclear inspectors crawling around Iran's facilities, and they're the ones who can say, yes, they've gone over this limit; no, they haven't. Iran may decide to kick them out, and that would be a very, very serious step that would indicate that maybe their intentions were changing.
SHAPIRO: NPR's Geoff Brumfiel, thank you.
BRUMFIEL: Thank you.
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