Generally speaking, there are three aspects to be considered in that matter. First and foremost, has Iran lost the capability to build an effective nuclear device in the next few years? In this context we refer to the capability to carry the device on a secure and accurate missile system. The second aspect would be the capability of Iran to return to enrichment of uranium on an industrial level. The third aspect is that of the psychological impact on the scientific scene as well as that of decision makers.
It is still early to provide a full assessment as to the impact, mainly because the extent of fake information emitted by Iran as well as Western entities of influence, trying to downplay the success of precise and well targeted, almost surgical, military activities.
In a nutshell, most, if not all major centrifuge production facilities have been heavily damaged or destroyed. Some of the production equipment, like suitable balancing machines, is almost irreplaceable. The substructure of these facilities is in ruins and any renewed activity will have to take place in new location. It will take many months if not years to restart these capabilities. When it comes to enrichment and conversion sites, it is quite clear that these have been completely destroyed to a level that makes no sense to rebuild in the same location.
The willingness to show high resilience might cause a wrong decision to reuse the same grounds. Fordow and Natanz took many long years to build and this time it will not be different. And then there is the loss of material. The question whether the US bombs hit the medium-high enriched Uranium seems crucial in the Media, but be sure that without certainty that the said material was in place, the B2 bombers would not have released the heavy ordinance. All the media hype about “no radiation” meaning no success, or the 16, some say 12 trucks two days before the bombardment that supposedly transported the 60% enriched uranium to another site, like many other bits of so-called info, are all irrelevant. Uranium 235 (enriched) is not highly radioactive and should not be measurable after the attack and one truck is more than enough transport the goods, surely not in those beaten-up heavy-duty soil moving trucks in the imagery. Last, but surely not least, is the long list of high-ranking scientists that have been eliminated. Surely you might think that knowledge is spread and dispersed and that these scientists have only of symbolic importance.
In this respect the experience of the scientists is crucial, especially when it comes to building parts of a bomb or making the calculations for criticality and yield for a device that could take down your own capital city and then some. These were the trusted experts with decades of experience and now they are gone. Not only them, but also almost anyone to have taken part in the weaponization projects of Iran in the past and up until today. This last part has great impact on motivation not because it is less important now to be a Shahid and die for the greater cause, but because of the deep infiltration into the most secret projects of Iran, that allows the enemy to pick and choose his targets with high certainty.
To sum it up, Iran was thrown back years and maybe more when it comes to enrichment, years and probably more when it comes to weaponization. When it comes to the psychological effects, it still remains to be seen. If it were Western scientists and project workers, it would be easier to assess, but this is a matter of national pride and it seems that severe safety issues put the lives of these people on the line. Even if you were involved more than twenty years ago, you are and will remain a legitimate target. This will not have a positive impact, quite the contrary.
Iran has tried to develop a nuclear device for decades, has renewed its efforts several times, invested billions of dollars and therefore will try again, as long as this regime remains in power. But this blow has put them back like it was never done before.