FACT BOX KEY Iranian Nuclear Issues

Reuters) - Iran's chief nuclear negotiator Ali Larijani resigned on Saturday.

In August, Iran agreed with the U.N.'s International Atomic Energy Agency to provide transparency about the scope of its nuclear programme.

The West suspects Iran is violating the Non-Proliferation Treaty by using a declared civilian nuclear energy programme as a cover for mastering the means to make atom bombs. Iran says it is seeking only an alternative source of energy.

An Iranian government spokesman said there would be no change in nuclear policy following Larijani's resignation.

Below are key issues the IAEA has about Iran's work which Western diplomats will want to see addressed by the agreement with Tehran:

* ADVANCED CENTRIFUGES

Inspectors have no access to sites where Iran has said it is trying to build P-2 centrifuges, which can refine uranium 2-3 times as fast as the antiquated, brittle P-1 model it is using for its initial enrichment programme.

* MILITARY LINKS

There has been intelligence, denied by Iran, about illicit efforts to "weaponize" nuclear materials, namely a "Green Salt Project" linking work on processing uranium ore, tests on high explosives and a missile warhead design.

* BLACK-MARKET IMPORTS

The IAEA says Iran has given inconsistent answers about when and why it appeared to obtain blueprints and parts for centrifuge enrichment machines from the former nuclear black market network of Pakistan's A.Q. Khan. Iran has also declined to turn over a document on machining uranium metal into hemisphere shapes suitable for the core of bombs.

* TRACES OF BOMB-GRADE URANIUM

Inspectors have sought satisfactory explanations on the origin of some particles of highly-enriched uranium found on some equipment used at atomic research sites.

* ACCESS TO SITES, OFFICIALS IN QUESTION

Iran has stonewalled IAEA requests to examine certain nuclear or related sites and interview officials deemed key to a full understanding of Iranian nuclear activity.

* UNDECLARED SITES

The IAEA cannot rule out Iran may have a military nuclear programme in covert locations. Tehran's cancellation last year of inspections at sites not declared to be nuclear, a move in retaliation for U.N. sanctions' steps, makes it much harder for inspectors to detect possible clandestine activity.

* DESIGN INFORMATION ON PLANNED NUCLEAR SITES

In April, Iran stopped giving the IAEA advance design data on planned nuclear sites. This raised concern about Iranian goals for its planned Arak heavy-water reactor, which Western leaders say could be used to make bomb-quality plutonium. Iran permitted a one-off return of inspectors to Arak in July.

* EFFECTIVE MONITORING OF ENRICHMENT PLANT

The IAEA has sought assured access, with camera surveillance as needed, inside the underground Natanz enrichment hall as the level of centrifuge activity has risen sharply this year. The IAEA has a regular presence only outside the hall.

* PLUTONIUM EXPERIMENTS

Iran has resolved the IAEA's question about tests with plutonium, a major fissile element in atom bombs.