On April 8, President Mahmoud Ahmadinejad of Iran paid a very public visit to Natanz, a uranium-enrichment facility - for peaceful nuclear power plants, Iran insists.
Western scientists intrigued by photos from Iran's nuclear site
By William J. Broad
Published: April 29, 2008
Barbed wire and antiaircraft guns ring a maze of buildings in the Iranian desert that lies at the heart of the West's five-year standoff with Tehran over its program to enrich uranium.
It is a place of secrets that Iran loves to boast about, clouding the effort's real status and making Western analysts all the more eager for solid details and clues. Tehran insists that its nuclear plans are peaceful. But Washington and its allies see a looming threat.
The sprawling site, Natanz, made headlines recently because Iran is testing a new generation of centrifuges there that spin faster and, in theory, can more rapidly turn natural uranium into fuel for reactors or nuclear weapons. The new machines are also meant to be more reliable than their forerunners, which often failed catastrophically.
On April 8, President Mahmoud Ahmadinejad visited the desert site, and Iran released 48 photographs of the tour, providing the first significant look inside the atomic riddle.
"They're remarkable," Jeffrey Lewis, an arms control specialist at the New America Foundation, a nonprofit research group in Washington, said of the photographs. "We're learning things."
Most important, the pictures give the first public glimpse of the new centrifuge, known as the IR-2, for Iranian second generation. There were no captions with the photos, so analysts around the globe are scrutinizing the visual evidence to size up the new machine, its efficiency and its readiness for the tough job of uranium enrichment. They see the photos as an intelligence boon.
"This is intel to die for," said Andreas Persbo, an analyst in London at the Verification Research, Training and Information Center, a private group that promotes arms control. His comment came on the blog site Arms Control Wonk.
One surprise of the tour was the presence of the Iranian defense minister, Mostafa Mohammad Najjar. His attendance struck some analysts as odd, given Iran's claim that the work in the desert is entirely peaceful in nature. In one picture, Najjar, smiling widely, appears to lead the presidential retinue.
Nuclear analysts said the tour in general opened a window into a hidden world previously known only to the Iranians and a few international inspectors.
"I don't see anything to suggest this is propaganda," said Houston Wood 3rd, a centrifuge expert at the University of Virginia. "They seem to be working on an advanced machine."
Such judgments rest not only on the photographic clues but also on the Iranian record of successful, if limited, enrichment and the reports of international inspectors, who have tracked Iran's bid to develop the new centrifuges.
Engineers use centrifuges for many applications, not just for enriching uranium. In general, the devices spin fast to separate all kinds of objects of differing mass and density - for instance, milk from cream or impurities from wine. To that end, centrifuges exploit simple laws of physics, doing so in ways that echo common experience.
A car that veers around a corner throws its passengers to one side. So, too, a centrifuge throws its contents off what would normally be a forward course. But it does so relentlessly.
Why do the contents separate? As Newton explained in his second law of motion, the more massive the object, the greater the tug. In the lurching car, an adult feels the force more than a child. In the centrifuge, heavy objects feel it more than light ones and, if possible, they move more vigorously toward the outer wall.
Nuclear centrifuges apply the same principle to uranium mined from the earth's inner recesses, spinning it into constituent parts.
Iran is separating U-235 from U-238. Rare in nature, U-235 easily splits in two to produce bursts of atomic energy. It also has three fewer neutrons than its cousin, making it slightly lighter and thus a candidate for centrifuge separation.
First, engineers turn the natural mix of uranium (0.7 and 99.3 percent, respectively) into a gas. Then, the centrifuge throws the heavier U-238 atoms toward the wall, letting the rare U-235 ones accumulate near the center. The results get scooped up continually. Rows of centrifuges repeat the process to slowly raise the rare isotope's concentration.
It seems easy. But the centrifuges spin at about the speed of sound, must work day and night for months or years on end and can easily lose their balance, tearing themselves apart.
"Our machines broke down frequently" in the program's early days, Gholamreza Aghazadeh, chief of the Iranian Atomic Energy Organization, said in a 2006 interview on state television. He said a study had traced the failures to centrifuge assembly when technicians with bare hands inadvertently left behind clusters of microbes.
"This little amount of germs," Aghazadeh said, was enough to throw the whirling devices off balance, leaving them in ruins. "When we say a machine is destroyed," he added, "we mean that it turns into powder."
In great secrecy, Iran began its centrifuge program in 1985, said inspectors of the International Atomic Energy Agency. It copied a Pakistani design, known as the P-1, that Abdul Qadeer Khan, a nuclear expert, sold on the global atomic black market.
The Iranian version stands more than two meters high, or over six and a half feet. Inside, a hollow rotor of aluminum spins the uranium gas to blinding speeds. Iran has installed 3,000 of the temperamental machines at Natanz, and has started to expand that setup to 9,000.
In recent years, Iran has tried to move ahead in sophistication with a newer centrifuge design based on Pakistan's second-generation model, known as the P-2. Its rotor is made of superhard steel that can spin faster, speeding the pace of enrichment while lowering the risk of breakdown.
But Iran had great difficulty building the machines and obtaining the special steel. Also in secret, it instead developed its own version, the IR-2. It is partly indigenous, signaling that the Iranians have achieved new levels of technical skill. If perfected, the IR-2 could accelerate Iran's production of fuel for reactors or bombs. Western experts said demonstration models of the IR-2 stand about one meter high - half the height of the P-1 - but they spin twice as fast.
"That's a lot," said David Albright, president of the Institute for Science and International Security, a private group in Washington that tracks nuclear proliferation. "It would produce about four times the enrichment."
The secret is carbon fibers, international inspectors said. The IR-2's rotor is made not of steel or aluminum but black carbon that forms an incredibly strong tube for its weight. Experts said it is also cheaper to make than steel tubes.
Of the 48 photographs Iran released, Western analysts gave special scrutiny to one showing Ahmadinejad and his entourage viewing a disassembled IR-2, its guts arrayed on a table. Clearly visible are its casing, inner rotor, motor and several other critical parts.
Arms Control Wonk, which is run by Lewis, of the New America Foundation, led a discussion of the photo. Most comments focused on the parts. But Geoffrey Forden, an arms expert at the Massachusetts Institute of Technology, noted that the display table also held an Iranian flag. "Indigenous manufacturing of sophisticated components is something to be very proud of," he wrote. "And showing them with an Iranian flag is a very good way of graphically proclaiming it."
Several photos gave glimpses of what Western analysts consider the part of a nuclear centrifuge usually kept most secret - its bottom bearing. That sounds prosaic. But the bearing is critical to battling the bane of relentless spinning: friction, which can slow, cripple or destroy machines meant to work flawlessly for years.
Iran's centrifuges, as is standard practice, have no physical support at the top. In a bid to eliminate friction, they have a magnetic bearing that holds the upper end of the rotor steady with invisible fields.
The rotor's entire weight rests on the bottom bearing, which consists of a single, thin, needlelike projection, its rounded head etched with spiral grooves to promote the quick flow of lubricating fluid.
One picture showed a young woman with a black Islamic shawl showing a bottom bearing to Ahmadinejad, who wore a white lab coat and what seemed like a pleased expression. Another bearing sat on the table between them.
Lewis said the presence of the tiny part was noteworthy because Iran once abandoned trying to build advanced centrifuges because of problems in making the bottom bearing.
Other photos showed rows of P-1 centrifuges as well as the new IR-2 model, apparently ready for testing.
A European centrifuge expert who follows the Iranian program, including the evaluations of the International Atomic Energy Agency, said difficult work remained on the IR-2. "They obviously have months, if not a year, of test work to do before they can consider proceeding with mass production," the expert said, who spoke on the condition of anonymity. More generally, analysts said, Iran is steadily gaining the industrial experience needed to make reactor fuel or, with the same equipment and a little more effort, bomb fuel - the hardest part of the weapon equation.
Uranium enriched to about 4 percent uranium 235 can fuel most reactors; to 90 percent, atom bombs.
Albright of the Institute for Science and International Security said that in one year 3,000 flawlessly running P-1 centrifuges could produce enough weapon-grade uranium for one nuclear weapon. Or, he added, the same could be achieved with 1,200 IR-2 machines.
U.S. intelligence agencies said the earliest Iran could make a nuclear weapon is 2009, but they consider 2010 to 2015 a more likely time frame. Iran insists it wants to make only reactor fuel for producing electricity.
Given the high stakes and the international jitters, why did Iran release the photos? Analysts cited everything from a spirit of cooperation to blasts of disdain.
"Maybe it's an invitation for engagement, or maybe it's just to show off their achievement," said R. Scott Kemp, a centrifuge expert at Princeton University.
Wood, of the University of Virginia, said the episode to him smelled of hubris. "It was amazing to me that they put the pictures out there," he said. "It's sort of a cocky thing. I would think they had more to gain by keeping their cards close to their chests."
By that analysis, the move trumpeted Iran's defiance of the West and the United Nations Security Council, which has imposed three rounds of sanctions on Tehran for its refusal to halt the uranium enrichment.
Some analysts saw the centrifuges as a continuing enigma. Ultimately, Iran could use them for good or ill, for lighting cities or destroying them.