They had access to Russian Scientists and technicians. If they wanted to make a weapon, I don't doubt that they could have. But, nuclear weapons are extremely expensive, both to produce, and to maintain. 

So, does this mean that Iran doesn't actually want a weapon? It just wants to sabre rattle? 

Or does it mean that Russia doesn't actually have the means or knowledge to produce one any more? 

Are they wanting to supply enriched Uranium to other players? 

I dunno, they've had plenty of time.