Why does Iran need industrial level uranium production
Why does Iran need thousands of centrifuges?
Well, I don't think that it is too hard to figure this one out. Iran is open about having a nuclear power industry. They have a bunch of reactors and eventually, they are going to need industrial level production of fuel.
The rub here is that they have thousands of centrifuges. Pardon me but if only one of them could produce militarily significant material is a few days, then my uncle Larry could hide a nuclear weapons program.
Granted, you need other stuff. Machine tools that are good enough to build telescopes and so on. You get the idea. It is the stuff that is needed to handle radioactive material that we can find and possibly deal with.
Really though, you need the facilities to do industrial level fuel production in order to do military production as well.
A single reactor may need 20 tons of low enriched uranium. However, natural uranium is 0.3% of the good stuff. Fuel is around 3% of the good stuff. Military grade is at least 20% of the good stuff and the closer one gets to 100% of the good stuff, the smaller the bomb will be.
They need the huge capacity because each pass through a centrifuge only enriches the uranium by about 0.01% Each centrifuge has two outputs. One is the input minus the good stuff that was removed. That is fed back into the process for further enrichment. The other is the input plus the good stuff that was enriched. That is passed further on to the system.
So the same system that can make 20 tons of 3% reactor fuel can also make a few dozen pounds of 90%+ in the same time. Having one means having the other. This is about as certain as having a car means that you can drive drunk. For people who might actually use nukes, I would say that the responsibility level is similar as well. Pretty much this is scary.