No one including the Iranians at their (nonexistent) equivalent of our Los Alamos Laboratory can make a nuclear weapon until they have managed to acquire multi-kilogram quantities of almost pure uranium-235, uranium-233, or plutonium-239.
For that reason, the Treaty on Nonproliferation of Nuclear Weapons required all signatories not already having nuclear weapons to conclude a Safeguards Agreement with the International Atomic Energy Agency, with a view to preventing diversion of “source or special fissionable material" to the production of nuclear weapons.
"Source" material is natural uranium in any form. "Special fissionable" material includes plutonium-239 and "enriched" uranium, in any form.
Pursuant to a Safeguards Agreement, IAEA inspectors perform periodic on-site inspections and continuous on-site monitoring to verify that “declared” source and/or special fissionable materials are not diverted to a military purpose.
After the Gulf War, the IAEA Action Team reporting directly to the UN Security Council discovered that Iraq had had a multi-billion dollar “undeclared” (and unsuccessful) program to enrich uranium for military purposes.
(This Iraqi nuke program of the late 1980s had gone completely undetected by U.S. and Israeli intelligence agencies. However, the U.S. and Israeli intelligence agencies did detect the nonexistent Iraqi nuke program of the late1990s.)
Hence the Additional Protocol to the Safeguards Agreement [.pdf], which provided IAEA inspectors much more authority, resulting in much greater transparency to nuclear programs and nuclear-related activities.
Iran signed an Additional Protocol in December 2003 and voluntarily agreed to abide by it, pending ratification by the Iranian parliament.
Iran’s original Safeguards Agreement merely required the disclosure of information on new Iranian facilities which would be processing safeguarded nuclear materials a few months before the materials were actually introduced. The Additional Protocol requires disclosure of that design information as soon as Iranian authorities decide to construct, authorize construction, or modify such a facility.
Iran’s Additional Protocol also provided for “voluntary reporting on imports and exports of nuclear material and exports of specified equipment and non-nuclear material.”
As a result of their voluntary compliance with the reporting requirements of the Additional Protocol, Director-General Mohamed ElBaradei was then able to report [.pdf] to the IAEA Board of Governors a year later that Iran had "failed in a number of instances over an extended period of time to meet its obligations under its Safeguards Agreement with respect to the reporting of nuclear material, its processing, and its use, as well as the declaration of facilities where such material had been processed and stored."
It should be noted that most of these failures were formally disputed by the Iranians as being subject to interpretation.
However resolved, ElBaradei was also able to report that within that year Iran had taken "corrective actions" with respect to most of those failures.
Finally, a few weeks ago ElBaradei reported that "since October 2003, good progress has been made in Iran’s correction of the breaches" that had been discovered in its basic Safeguards Agreement "and in the Agency’s ability to confirm certain aspects of Iran’s current declarations" made under the Additional Protocol.
In fact, ElBaradei reported that the remaining issues under the Iranian Safeguards Agreement and its not-yet-ratified Additional Protocol "will be followed up as a routine safeguards implementation matter."
So there you have it. As of a few weeks ago, not only had Iran corrected the "breaches" that occurred before they signed the Additional Protocol in 2003, but those issues that had arisen since as a consequence of their voluntary adherence to the Additional Protocol were being routinely followed-up.
After more than two years of intrusive go-anywhere see-anything ask-anybody inspections under the Additional Protocol, the IAEA has yet to find any indications that there are, now, in Iran, any undeclared materials or activities that should have been declared, nor any indications that any declared materials have been diverted for a military purpose.
The Additional Protocol concept was a success in its first serious application. The IAEA was now not only able to verify the non-diversion of declared nuclear material, but also to provide some assurances of the absence of undeclared nuclear materials and activities.
So why did the IAEA Board then plead incompetence [.pdf], finding that ElBaradei’s positive reports on Iran’s Safeguarded programs had, nevertheless, resulted in an "absence of confidence" on the Board’s part "that Iran’s nuclear program is exclusively for peaceful purposes" and ought to be referred to a more competent authority "as a threat to international peace and security"?
Well, one thing seems certain: the Iranian parliament will never ratify those incompetents’ Additional Protocol.