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How Did Iran Hide All Those Centrifuges?

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This week's multilateral agreement to limit Iran's nuclear capability has put the country's nuclear program at center stage. While plenty about the deal's ultimate effectiveness and Iran's intentions has yet to be answered, the process of bringing a once-covert nuclear development under international monitoring begged the question, how did they keep those facilities secret for so long? According to Dr. Jeffrey Lewis, a scholar researching non-proliferation issues at the Middlebury Institute of International Studies at Monterey, the process by which Iran built these hidden nuclear facilities and labs may not be as complicated as you think, and often utilized private contractors who weren't explicitly part of the military or security apparatus. According to Lewis, there were two main processes used to build these vast, underground enrichment sites.

"The vernacular of nuclear design, that's an interesting question," he says. "There is such a distinct quality to these facilities."

The first process, cut and cover, is more of a brute form of construction, basically digging a hole in the ground and covering up the entrance with a roof buried under the soil. It was used to construct the Natanz Enrichment Complex built in central Iran in 2002 for a roughly estimated cost of $55 million and the target of the Stuxnet computer virus. This method isn't the most secure, since it's hard to slip a massive hole in the ground past satellite surveillance (that problem also limits how deep you can feasibly dig). Once the underground building/bunker has been dug—Natanz is comprised of three subterranean buildings that can hold more than 50,000 centrifuges—the top is covered in concrete and rebar, reinforced to make it more secure to weapons and bombing, and then topped with a camouflaged building, like a shed or small warehouse, that serves as an entrance. That building included a sizable ramp at Natanz, since they needed trucks to drive centrifuges in and out of the facility.

The second method, horizontally tunneling into a mountain, helped create the Fordow Fuel Enrichment Plant, a former base for the Islamic Revolutionary Guard Corps near the city of Qom (it's also referred to as Fordo). Where as the cut and cover method just requires standard construction equipment and machines, tunneling requires special industrial drills. That can be a bit of a tip off; Lewis mentioned a case where United States intelligence was able to determine the size of a tunnel the South African government dug in the Kalahari Desert for nuclear testing by the number of spent drill bits used in its construction. By their nature, these buildings are harder to uncover, since they only need a small outcropping around the entrance to help guard against erosion or a landslide.

Former Iranian President Mahmoud Ahmadinejad touring the Natanz site. Photo courtesy of Jeffrey Smith.

For many countries, constructing these facilities may be ordered and overseen by the military, but private contractors usually do all the work. Lewis says in Iran, the Atomic Energy Organization contracts with civilian companies, such as Kimia Mabaan.

"It's actually pretty routine stuff," he says. "Countries just often don't have specialized military units to do construction. They just hire mining companies and those with expertise."

Lewis says that while a mixture of satellite surveillance, human intelligence and revelations by allies in the country help pinpoint where these secret buildings are located, they often have distinctive designs that function as tipoffs to their secret purpose.

"Its funny, military organizations can't help themselves," he says. "If you go look at a mine or industrial facility, there isn't much landscaping, for instance. But military guys need to make it look nice and orderly. There are always giveaways."

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