ShapurII
Trusted Member
It is impossible to answer your question because first of all, your question is not well-defined.
How many centrifuges are required? The more, the faster. But let's study it in more detail.
Scenario I: Iran has access to nearly 440 kg of 60% HEU
This is the most optimistic scenario. So far evidence suggests that our HEU has been buried under debris and is inaccessible, but this is the only scenario where Iran can still build an atomic bomb. So, let's study this first.
A) How much uranium will we get? We have 440 kilogram of 60% HEU. If we assume that we are enriching it to 90% with a tail assay of 0.23%, we will get nearly 290 kg of 90% HEU.
B) How many centrifuges do we need? To get from 440 kilogram of 60% HEU to 290 kilogram of 90% HEU in a year, we will need 2,200 SWU UF6/year. That is about 370 IR-6 centrifuges. If we want to do this in just one month, it depends on your configuration and cascading, but you can more or less claim that your output is added linearly in the ideal theoretical situation. So, you will need 26,400 SWU UF6/year. That is about 4,500 IR-6 centrifuges.
C) How many advanced centrifuges can Iran have? Prior to the attack, the ICAC at Natanz boasted that it could assemble 60 IR-6 centrifuges per day. We do not know of the extent of damage to ICAC. Parts of ICAC had been moved underground due to an Israeli sabotage operation years ago. Again, we're in the dark but Iran would need about 11 weeks to produce enough IR-6 centrifuges to reach the required capacity for uranium enrichment.
So, the short answer is in the most optimistic scenario, if we assume Iran is still in possession of the 60% HEU it stockpiled and it can still produce IR-6 centrifuges, it would take from one month to three months to convert ~440kg 60% HEU to ~290kg 90% HEU.
D) Can Iran build a bomb in 3 months? Short answer: Probably not. Even if Iran somehow enriched its stockpile to 90%, the enriched uranium will be in the UF6 gaseous form. It has to be converted into uranium metal before it could be weaponized. And Iran's only uranium conversion facility has been destroyed. Besides that, if you want to build a boosted fission weapon, you will need deuterium and tritium for that. Iran's heavy water production has been destroyed as well. So, if Iran doesn't have other undeclared facilities for those things, we will still be unable to produce a nuclear weapon.
Scenario II: Iran has to start from scratch
This seems to be the most realistic scenario now. The short answer is that Iran will never become a threshold nuclear state again. Why?
First, you have to mine uranium. Fortunately, our uranium ores like Saghand haven't been targeted, it seems. After you have mined uranium, you need milling to convert it into yellow cake (U3O8). I knew of two yellow-cake production facilities at Ardakan and Bandar Abbas and both have been hit from what I remember. So, that's your first obstacle.
Second, imagine you have enough yellowcake. After all, Iran imported tons of yellow cake from Russia after the JCPOA and maybe we still have some yellow cake left. You will still need to refine it into UO2 and UO3, and then convert it into green salt (UF4) and eventually UF6 gas to feed it into your centrifuges. We have lost critical components of this chain as well.
So, in this case, the short answer seems to be never, because as Pezeshkian said, even if we attempt to rebuild our nuclear infrastructure, there is no guarantee that they will not bomb them again.
There are other ways to produce HEU, such as laser isotope separation. We have experimented with this. Fortunately, the Shah that these fools here like to badmouth had imported LIS technology in 1975 from the US and Iran has experimented with it in Lashkar Abad in 2003. It can help us circumvent many of these obstacles, but it is something that Iran has to do clandestinely and if we're caught, it may have severe consequences for Iran.
