“This room could include machinery to convert green salt into metallic form,” Aitan continued, “but if they go that route, it will be a tight fit. They would have to bring in kilns to melt the green salt and fuse it with magnesium. To accomplish that they will need to add a lot of ventilation that is not reflected in their plans. Also, there is a smaller room that could have several possible uses, including storage of depleted uranium hexafluoride, or storage of highly enriched uranium dioxide or green salt, or even warhead storage. Plus they have a separate processing hall which is being built above ground but will probably be buried in the future. This hall will receive shipments of uranium hexafluoride that is enriched up to twenty percent. The hall will have an autoclave to heat granular hexafluoride into gaseous form and feed it through piping directly into the centrifuge cascades in the main chamber.
“Interestingly, the plans show that the secondary enrichment hall, which is designed for less than three thousand centrifuges, will be separated from the rest of the rooms by a thick wall. My guess is that the secondary hall is for inspection purposes if they have to let in the IAEA.” Aitan referred to the International Atomic Energy Agency, the organization that oversees publicly declared nuclear programs on behalf of the United Nations.
“Why do you say that?” asked Raibani.
“Because the main complex has six entrances into the mountain which funnel into three openings into the chamber,” Aitan replied. “All three openings are into the secondary enrichment hall area. The main chamber is separated by a wall that has a couple of openings that look like they will be hidden. So call it an educated guess. Does that answer your question?”
Raibani nodded.
“The primary enrichment hall is designed for 8,856 centrifuges.”
“What about this second complex you mentioned?” asked the prime minister. “How long have we known about this?”
“Well, we learned about the second complex when we obtained the engineering plans in September 2007. I have discussed the second complex before,” Aitan answered.
“With me?”
“Yes, sir. Right here in this room.”
Cohen shrugged his shoulders. “I must have misunderstood what you were saying.” He placed his cigar between his lips to inhale the smoke.
“I apologize for any lack of clarity. The second complex is six kilometers southwest of Manzariyeh Airport. It is on the northern edge of the Baqarebad military complex, built by Iran to store missiles and warheads. The tunnel complex here was originally dug out ten years ago to store important government documents. But the new plans are for a smaller version of complex one. My guess is this is intended to be the final warhead fabrication, assembly and storage facility, but it could just be a back-up to complex one. To date, we haven’t seen any construction, but the plans call for a tripling in the size of the underground chamber.”
“What is the timing for each complex to come online?” asked the defense minister, making sure his unwitting surrogate made the right points.
“Their focus is on the first complex and we estimate construction and the placement of centrifuges to be completed in about eighteen months. The second complex is clearly a low priority for them. Our best guess is that they are waiting to begin real work on it after they are finished with the first.”
“How deep is the first complex?” continued Avner.
“Well, the entrances are all at the nine hundred twenty meter contour line.” Aitan raised his left hand up in the air. His fingers were straight and his palm was face down and parallel to the table. “The floor of the main chamber is eight hundred and eighty-six meters above sea level.” He dropped the level of his hand a few inches to visualize the drop in altitude from the entrances to the level of the chamber. “The finished height of the chamber is four meters. The minimum amount of earth above the chamber is the point over the southwest corner. At that point, there is fifty-two meters of volcanic basalt. Fordow is part of a geological formation known as the Oromeieh-Dokhtar belt. It is the end result of ancient volcanic flows.” Aitan had no notes. All of the information was stored in his head. Everyone in the room knew that if Yavi Aitan read it once and committed it to memory, then the information would be locked away as if on a hard drive.
Aitan turned his face to look at Avner. The younger man continued. “That depth is equal to one hundred fifty-five feet of earth at a minimum at the southwest corner. The maximum depth to reach the chamber is seventy-eight meters, or two hundred fifty-seven feet of basalt rock above the primary enrichment hall. If I recall correctly, the GBU-28 can penetrate, at best, only one hundred twenty feet of earth. And that assumes the bomb is dropped from at least fifty thousand feet.”
“How long?” The words were in the direct style of Benjamin Raibani. The metronome was ticking again.
“Eighteen months as…”
“No,” Raibani interjected. “Once they have Fordow operational, how long to get to ninety percent enrichment?”
Yavi Aitan pursed his lips. “That depends. Let me make a couple of assumptions.” Aitan pivoted his left forearm upward from the table on its elbow. He stuck his thumb upward. “First, assume that they enrich to twenty percent at Natanz, which I must point out they have not yet done to our knowledge.” Aitan extended his left forefinger. “Second, assume that we are right on the number of centrifuges inside Fordow and that they are all operational.” Aitan extended his middle finger. “Third, assume they are using their first generation centrifuges inside Fordow, what they call the IR-1. This last assumption is key and is in our favor. The IR-1 is not very efficient.” Aitan extended his next finger, his pinky finger now struggling to stay folded. “And finally, assume that they have a reasonably advanced implosion design that only needs twenty kilograms of ninety percent uranium.”
Raibani interjected. “How do you know the efficiency of their centrifuges?”
“Well, we have a lot of data on Natanz from both the IAEA and other sources. We know the statistics for the amount of base feedstock, the product, which has been three point five percent enriched uranium and the tail. We have even been able to get some of the tailings from Natanz to Dimona for analysis.” Aitan paused. The look in Raibani’s eyes asked the question that he didn’t need to verbalize. “Excuse me, I am hanging around with too many nuclear scientists and physicists these days. The tailings are the depleted uranium byproduct of the enrichment process.
“In a nutshell, you start with natural uranium ore which is ninety-nine point three percent uranium 238 and only seven-tenths percent uranium 235. For a weapon, you want uranium enriched to about ninety percent uranium 235. At Natanz, they use gas centrifuges which spin uranium molecules at a high speed. The heavier 238 molecules migrate to the outside of the centrifuge tubes and the lighter 235 molecules migrate toward the center of the tube. You then collect the separated molecules. The enriched 235 molecules are sent downstream and the depleted 238 molecules are sent back to repeat the process. Eventually the depleted uranium 238 is no longer needed and sent to storage in steel drums. This is the tail.”
Aitan glanced at Zvi Avner. The defense minister very subtly rolled his finger, letting Aitan know to speed things up. Aitan returned to the immediate question. “With those assumptions, if the Iranians start with one hundred twenty kilograms of twenty percent enriched uranium, they can produce twenty kilograms of ninety percent uranium inside Fordow in less than a month.” Yavi Aitan let that sink in for a moment. “If they can upgrade their centrifuges as they are trying hard to do — and we are trying hard to keep them from doing — the process inside Fordow would take under a week.” The room was quiet, each man’s thoughts lost in a different scenario. But each scenario had the same bad ending.