Iran holds back nuclear details, IAEA says

The report said Iran still has not disclosed full information about its work on high-explosive testing and missile design work, as well as the “green salt project” studies — research involving uranium tetrafluoride, a precursor to uranium hexafluoride, which is used in gas centrifuges to make enriched uranium.

     Basically they show the International Atomic Energy Agency their paperwork for clean and peaceful Nuclear technology, but nothing about their other projects. They refuse to show them that information. Why do you think? See section on Countries of Interest for further understanding.