RENEE MONTAGNE, host:
Early this week, U.S. intelligence agencies reported that Iran ended efforts to build a nuclear weapon in 2003, but Iranian engineers continue to make uranium fuel for what they say is peaceful nuclear power. Experts point out that enriching uranium for fuel leaves a big part of the weapon's apparatus intact.
NPR's Christopher Joyce reports.
CHRISTOPHER JOYCE: You make nuclear fuel for a power plant or material for a bomb the same way. You turn uranium into a gas and then run it through a series of centrifuges. These are essentially tubes that spin tens of thousands of times a minute. That separates out the isotope you want - Uranium-235. Stop spinning when your gas gets to about five percent U-235, like the vermouth in a dry martini, and you've got fuel for a power plant. Spin some more, to 85 percent U-235, and you've got the stuff of bombs.
The International Atomic Energy Agency, the IAEA, discovered Iran's centrifuges in 2003 and said they had stopped enriching. Iran did for two years then they resumed.
According to Michael Levi, a physicist with the Council on Foreign Relations, you can't just flip a switch and expect these machines to just start up again.
Dr. MICHAEL LEVI (Physicist, Council on Foreign Relations): If your washing machine is slightly off balance, it's going to start walking across the floor. Now what you've got in a centrifuge plant is you've got these tubes spinning at incredibly high speeds. This is your washing machine on steroids. And if you don't get it balanced just right, it can go flying and crash into the other pieces. Iran had problems with crashing centrifuges early on. It appears to be have - had fewer recently, but it also appears, according to certain reports, that it's been operating these at a lower speed.
JOYCE: Lower speed means less efficiency. Nonetheless, Iran has built more centrifuges, perhaps as many as 3,000 of them, and is studying how to make them work better.
Levi and other nuclear experts say that even if Iran has, in fact, stopped designing a weapon, the enrichment process is really the biggest single step toward making one.
Pierre Goldschmidt is with the Carnegie Endowment for International Peace and was a senior official at the IAEA.
Mr. PIERRE GOLDSCHMIDT (Visiting Scholar; Carnegie Endowment for International Peace): A nuclear weapons program has essentially three components: its nuclear material, weaponization activities, and then the delivery systems. And clearly, Iran is still working and making progress on nuclear material production and on delivery system with ballistic missiles.
JOYCE: Goldschmidt says the U.S. National Intelligence Estimate this week did not clearly distinguished that.
Mr. GOLDSCHMIDT: They should make a distinction between the intention to develop nuclear weapons and the intention to develop a nuclear weapons capability.
JOYCE: He says there is no evidence that Iran has abandoned efforts to get that capability. And President George Bush noted in his press conference this week that Iranians still have the knowledge to build a weapon. Nuclear scientists point out that lots of people have that knowledge. You could find bomb designs and enrichment primers on the Web. The Iranians got a lot of their knowledge from Pakistan, including designs for centrifuges. But they still do not have, says David Albright, head of the Institute for Science and International Security, and a former weapons inspector, is experience.
Mr. DAVID ALBRIGHT (Head, Institute of Science and International Security; Former Weapons Inspector): So the sections are going to break more, they're going to run less efficiently. But I think overall they're going to work adequately. They'll succeed. They could have a technical capability to reliably enrich uranium and we see it could happen as - next year.
JOYCE: Albright says Iran has also been accumulating parts to build even more centrifuges. Once they learn how to run them reliably, he says, it might take Iranian scientists as little as a year to produce enough highly enriched uranium for a bomb.
Christopher Joyce, NPR News.
MONTAGNE: That intelligence estimate Chris just spoke about represents the collective opinion of the U.S. intelligence community. You can read about what goes on in the making of the National Intelligence Estimate at npr.org. Transcript provided by NPR, Copyright NPR.
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