Ben Raibani started to ask a question. Aitan raised his hand to acknowledge his thoughts before he spoke. His tone suddenly changed from authoritative to that of a professor in front of a class. Aitan continued. “Rotor tubes inside a centrifuge are spinning at great speeds. The longer and wider the tubes, the more efficient is the centrifuge. But a long rotor tube is also subject to greater levels of vibration stress. So one way to reduce that stress load is to cut the tubes into shorter sections that are then connected together with joints that combine strength and resilience. These joints are known as bellows. The bellows in the IR-1 combine four aluminum tubes into a single rotor that is one point eight meters long.
“So bellows provide the critical internal structural support for the rotor tubes as they spin and incur vibrations. They allow for longer and larger rotor assemblies. Maraging steel is just a very strong alloy of steel that has a high degree of resistance to distortion. The Iranians use grade 300 maraging steel that has about eighteen percent nickel, nine percent cobalt and four and a half percent molybdenum.
“They have to import all of the maraging steel they use. This type of steel is controlled by the IAEA and is technically banned from Iran. But they use a number of front companies operating outside Iran that acquire controlled materials like maraging steel. They have purchased this steel from mills in Japan, China, Russia and North Korea. Fortunately, international pressure has gotten all but China and North Korea to stop selling. The large Chinese companies won’t sell to Iran but some small steel mills will still do business with a wink and a nod assuming they get a nice profit in the process. We are working hard to end these sources. North Korea continues to supply some but their mills have spotty quality and we are usually able to interdict their shipments. The North Koreans have become leery as a result of our interdiction success. The bad news is that the Iranians are planning on building an indigenous capability. We are watching those developments very closely and will take action as necessary.
“The same analysis applies for carbon fiber, which can be used for rotors and bellows. The fact is that the most advanced centrifuges in the world are now made of carbon fiber. But fewer than a dozen countries in the world can manufacture quality carbon fiber and none of them will knowingly sell to Iran. Just like the situation with maraging steel, we have heard chatter that they are planning on building an indigenous factory. This is very early, so we will have to wait and see what they do.”
Eli Cohen interrupted Aitan’s review. “How did Myrtus work?”
“I’m sorry, sir, I thought I reviewed that at the beginning.”
“No. I mean, how did the virus accomplish the destruction of two thousand centrifuges?”
“Oh. Well, the key, Mister Prime Minister, to understanding how Myrtus does what it does is to understand how a centrifuge works. It’s a precision machine. The internal rotor is spinning at very high speeds, over one hundred thousand RPM in top quality machines. The faster it’s traveling on the periphery, the more efficient the enrichment process will be. But to achieve higher rotational speeds means that the machine must be built to ever tighter tolerances. The slightest vibration at a speed of, say, sixty thousand RPMs, becomes a destructive vibration at seventy thousand RPMs. Plus, every rotor has certain frequencies at which there is a natural harmonic vibration, known as resonance. These types of vibrations place huge stress on the rotor and its components.
“The rotor assembly is the key and it has to be perfectly balanced and aligned. As a result, a great deal of effort is taken to balance the rotor for the design speed. The best analogy I can give you is when you have your car wheels aligned. They may be perfectly aligned at one hundred kilometers per hour but then you get a vibration at one hundred thirty or one forty. That vibration, if you continue to drive at that speed for too long, can damage the original alignment and create a vibration when you are back at one hundred.
“We created — I should be fair and say the Americans created — a program that changes the converter frequency, or the rotational speed, to induce a new vibration for a period of time. If you want the scientific detail, the Americans calculated the average flexural resonance frequencies of the rotor for the IR-1. Notice I used the plural. There are a number of harmonic resonance frequencies for the IR-1. The Iranians operate their centrifuges at a frequency that is just below the fourth resonance frequency. Myrtus increases the frequency to the point of the fourth harmonic. This induces what is called an s-form deformation in the rotor. This particular resonance puts significant stress on the rotor, the bellows, the bearings and even the motor.
“In non-scientific terms, any imperfection in the rotor assembly is magnified by the change in rotational speed. Myrtus does this briefly then returns the rotor to its design speed for four weeks. Then the program slows the rotor down to a very low speed. This does two things. First it induces more vibration imbalance by passing through the first three resonance frequencies, but second, it allows the uranium hexafluoride to condense inside the rotor. Hexafluoride gas is highly corrosive, so doing this can significantly accelerate the corrosive impact of the gas inside each affected centrifuge.
“But we have added a second piece of software to Myrtus. This we came up with ourselves. Not even the Americans are aware of it. The software very quietly adjusts control valves in the piping to allow for a small amount of oxygen to be introduced in each cascade.” Aitan looked at the blank stares and decided to provide more background. He thought for a moment how best to explain it. As he spoke, he was using his hands to illustrate. “Rotors are spinning at great speed. That speed generates tremendous friction with the air, producing drag, heat and stress just like the leading edge on the wing of a supersonic fighter. To eliminate this, the rotor is inside an airtight vacuum casing. Vacuum pumps in the piping and molecular pumps in each centrifuge run continuously to maintain the vacuum and remove any uranium gas that escapes from the rotor assembly into the vacuum of the outer casing.
“What we have done is to take control of the inlet valves into the vacuum system, which is a centrally managed network of piping for each cascade. We are not eliminating the vacuum completely, we are just making it a partial vacuum. This introduces friction which increases the stress on the rotors and their motors by a meaningful amount. Myrtus also takes control of the vacuum pressure warning systems and makes sure they register that a proper vacuum is being maintained.
“Over time, we expect that this will cut the life expectancy of each centrifuge by at least fifty percent. We think that Iran will have a hard time finding this second method of attack, even after they uncover the core software worm. This method hides elsewhere in a very clever location and the injection is done via an encrypted code that we don’t think anyone is capable of breaking, maybe with the exception of the NSA — and I am sure they won’t be helping Iran on this. We have actually been able to refine this attack on infected machines by using information sent to us over the internet and then modifying the code.” Aitan looked around the room. He was very proud of what the team at Unit 8200 had accomplished, like a teacher whose student was accepted into a prestigious university. “Questions?”
“Yes,” responded Ben Raibani. “Have the Iranians figured out what is happening with Myrtus yet?”