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Comment by mjburgess | Hacker News Reader

It's important to add that it isn't just concrete -- but the relevant installation was under ~100m of granite.

There were also a caravan of trucks removing large amounts of items before the raid. There are estimates Iran has 600 kg of enriched uranium. One kg of uranium is about the size as a kg of gold, or the size of a phone. So they probably removed some of the harder to replace equipment. Could have been anything. Servers, weapons and ammunition, etc.

Centrifuge manufacturing has come a long way in the previous 20 years. Precision machining has newer models with up to 200,000 rpm. "Centrus (formerly USEC) plans a centrifuge with 60 cm diameter, 12 m height and 900 m/s peripheral speed." Even with their centrifuge manufacturing facilities hit/destroyed, they could reconstitute within a year or two and continue the refinement process.

https://en.wikipedia.org/wiki/Zippe-type_centrifuge

200,000 revolutions per minute?

Boggles the mind that this is 3,333 revolutions per second.

I'm not saying you're wrong but a quick check of a few LLMs says that 90,000 RPM is widely cited as the practical upper limit for current operational centrifuges in facilities like those operated by Urenco, Rosatom, or Orano.

900m/s is approx Mach 1.5.

You can buy a lab centrifuge (such as Optima MAX from Coulter) that does 150 000 RPM, (or as a more useful measure, about a million g). These are often used for virus purification.

But isotope separation is usually done on UF6, which is a gas. These centrifuges work a bit differently, see https://en.wikipedia.org/wiki/Zippe-type_centrifuge

While I don't know much about centeifuges, I'm still in awe that this Hikoki handheld blower does 90k rpm: https://www.hikoki-powertools.com/products/powertools/li-ion...

That's not a typo, I actually own this device and couldn't believe at first this thing spins with ninety thousand rpm. A lot has happened since my last 5400rpm hdd bit the dust.

I'm actually wondering why it's "only" buried under ~100m (which is already on the higher end of the depth estimates).

Why not pick a mountain where you install the bunker 300m under the peak ?

The way I understand it, is that they drill horizontally, so it doesn't really matter how high the mountain is, but it does matter how high it is for protection obviously.

The specific composition of this specific mountain range in Fordow made it almost ideal for this purpose. It's not only the depth, but also the rock type, the fact that the rock layers were compressed, and overall accessibility - all of these limit the selection space for 'deep holes in the ground for building a nuclear facility'. Also, you need to take into account an important fact: It is in Iran... There may be other, better locations on Earth, but having sovereignty on the land is key:)

Well, what they choose to dig was deep enough, wasn't it? And that's really what matters.

The mountain itself is ~80m to base, and the 20m comes from assuming that trucks are just driving down into it (so a gradient down to -20m on the road). If you had deeper, you'd need to then have more complex transport mechanisms underneath the mountain.

The assumption is that they haven't done that -- but it's not implausible to add some multiple of 10m on to the estimate.

I'd imagine they studied bunker buster arms in the design, and very probably concluded, that there wasn't much need to go very deep. Demolishing 80m of granite alone is a nuclear-sized problem, +20m and maybe 10m of specialised concrete, i'd imagine is fine.

It's also highly likely that the design of the installation is robust against collapse, eg., designed so that small areas can collapse independently. So even with arms which could penetrate that deep, you'd need a large number.

I think it's plausible that the entire supply of bunker busters the US currently has could do the job, but I highly doubt the US would risk depleting its capacity on a "maybe" of this kind.

The whole operation was a performance to try a carrot rather than stick approach with israel

But why not pick another mountain of ~300m ? Are there any downsides to that ?

That would be beyond any reasonable doubt that it cannot be destroyed (even with nukes ? ), which would make more sense to me. And the country is surely big enough to find one suitable for that.

Important to add that they targeted the ventilation shafts. So 100m of air, not granite.

I'd assume the Iranians have seen Star Wars - and know not to build convenient shafts that go straight down to the stuff which their enemies want to destroy.

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