I hate to disagree with Gromit, but the Iranians are not likely to volunteer the evidence.
What is true is that they have a far larger enrichment operation than they could ever justify for power generation. Also 20% enriched uranium is not needed for power generation, and only tiny quantities can be justified for medical purposes.
They have been offered a supply of power generation grade uranium if they will cease enrichment, which they have refused.
Only someone with his head buried in the sand could fail to see what their intentions are.
If it walks like a duck, and quacks like a duck, it sure isn't a peaceful power generation programme.