60% enrichment level is significantly higher than what’s required for peaceful purposes. To say that it’s not weapons grade is just disingenuous.
It turns out there's a big gap between most peaceful purposes and weapons grade, and this was in that gap.
> Uranium with enrichments ranging from 40% to 80% U-235 has been used in large amounts in U.S. thermonuclear weapons as a yield-boosting jacketing material for the secondary fusion stage
Source: http://nuclearweaponarchive.org/Nwfaq/Nfaq6.html#nfaq6.2
edit: phrasing. it feels like we're going around in circles nitpicking based on a poor framing and the tendency for innuendo on this topic
Also, you can use 60% enriched uranium in the primary stage at the cost of a much larger, less efficient, and dirty device.
All modern nukes are two stage designs, Iran would be insane not to have a fusion stage. It would basically be a Hiroshima style dirty bomb with just 1.5% fissible mass actually fissioned.
Hiroshima was pretty terrible as it was. And I thought the capability that everyone focuses on because it gets nations a seat at the nuclear table was just basic fission weapons. But please correct me if I am wrong.
The bottleneck is UF₆ centrifuges, not the modeling. They're definitely aiming for a fission-fusion design: "The sources note that Iran has attempted to produce deuterium-tritium gas on its own inside Iran - with the help of Russian scientists - but has so far been unable to do so, and due to pressures by the Iranian leadership to accelerate the weapons production program, decided to try to purchase this substance abroad." [0]
India and Pakistan did their first tests ~30 years ago, a lot has changed since then and if you're building a nuke in '25 might as well spend some cash on a simulation cluster and buy some multiphysics simulation software from Russia..
[0] The sources note that Iran has attempted to produce deuterium-tritium gas on its own inside Iran - with the help of Russian scientists - but has so far been unable to do so, and due to pressures by the Iranian leadership to accelerate the weapons production program, decided to try to purchase this substance abroad.
Maybe I'm just putting too much weight on the trials and tribulations of developing the first fusion bombs, and the details of solving or working around those problems is widely known in the right circles these days? Plus advancements in simulation accuracy?