Iran could continue to import all the Moly 99 they need for about $1 million a year. That's nothing, why not do that? Why give up all that uranium, that cost the Iranians hundreds of millions to enrich to 4.4%?
Because Iran is stuck at 4.4% LEU, per my previous post and need much more knowledge and time to get the "lead" (MoF6) out of their UF4 in order to convert it into UF6.
There is also a political problem in Iran = hardliners (Ahmadinejad) vs. moderates (Rafsanjani). If Iran keeps the uranium, they will, verrrrry slowly, get weapons-grade uranium. The Mullahs know that the hardliners, led by the Revolutionary Guards, will contol the nukes and take over and radicalize the government and the entire Middle East. That whole Hidden Imam, Armageddon thing.
The Mullahs are barely in control now and they know that actual nukes will cause an internal revolution in Iran.