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Claims about Iran's nuclear program are flying thick and fast. Leaked material shows that Iran is undoubtedly working on an atomic bomb – or, no, wait! – Iran has never had a nuclear weapons program and has no intention beyond peaceful civilian nuclear power. Which is it?

What we reliably know about Iran's nuclear program comes mostly from quarterly reports issued by the International Atomic Energy Agency (IAEA) and declassified versions of national intelligence estimates. Here's a summary.

Iran has one civilian nuclear power plant at Bushehr, on the Persian Gulf. Construction began in 1975, with German and then Russian firms involved. It has been operating since September 2011. A research reactor, provided by the United States in 1967, is located at the Tehran Nuclear Research Centre. The research reactor produces medical isotopes.

Concern about possible nuclear-weapons development arises from Iran's program to acquire facilities to produce enriched uranium and plutonium, which can be used in nuclear weapons. A number of these facilities have not been declared by Iran to the IAEA as required by Iran's signing of the Nuclear Nonproliferation Treaty.

Centrifuge enrichment plants at Natanz and Fordow, both near the city of Qom south of Tehran, produce uranium with higher levels of the fissionable uranium-235 isotope. Three to five per cent uranium-235 is suitable for the Bushehr and other power reactors, but the research reactor requires 20 per cent enrichment. Most of the work in enrichment goes into increasing the uranium-235 from its natural 0.7 per cent to reactor grade. Increasing from reactor grade to weapons grade, above 90 per cent, can be done more quickly. The Fordow plant is located inside a mountain. Iran says that an improved centrifuge version is being installed.

The February 2013 IAEA report says that Iran has on hand 5974 kg of uranium enriched to 5 per cent or less in the form of uranium hexafluoride and 167 kg enriched to about 20 per cent. Of the higher enriched material, 113 kg has been fabricated into fuel plates for the research reactor.

Iran is building a heavy-water reactor at Arak, to the west of Qom. Heavy-water reactors use natural, unenriched, uranium. They are particularly suited to plutonium production, although Iran says that the purpose of this reactor is to produce medical isotopes.

Iran also operates a fuel fabrication plant and a plant to convert yellowcake, a solid, to the gaseous UF6 spun in the centrifuges.

A number of Iranian research facilities can handle highly radioactive materials. Industrial facilities have tested centrifuges, which Iran manufactures. When the IAEA requested to visit two of these facilities, Iran stalled until the buildings and surrounding area could be cleaned up so that it was less likely that the IAEA would find evidence of non-declared work. In one case, the IAEA could not find evidence, but in another, it found enriched uranium, indicating that centrifuge tests had been carried out.

The IAEA has evidence that Iran has done research related to developing nuclear weapons. The conclusions of both the 2007 and 2011 US National Intelligence estimates are that Iran had an active nuclear weapons program before 2003, when it stopped work in that area. The IAEA is concerned that work in some of the areas may have continued after 2003.

The IAEA refers to this work as "possible military dimensions" of Iran's nuclear program. Again, Iran has acknowledged some of this when confronted with evidence, but continues to deny other aspects. This work includes experiments and procurements that could have other applications than nuclear weapons.

Iran received information on centrifuge design and manufacture from A. Q. Khan, the Pakistani scientist who developed an international network for clandestine nuclear weapons manufacture. The package included information on producing uranium metal hemispheres, useful only for weapons. A similar package provided to Libya included the design of a nuclear weapon.

Additionally, the IAEA has information that Iran experimented on separating plutonium from irradiated fuel, developing exploding bridgewire detonators, and multipoint initiation of a spherical explosives assembly like that of a nuclear weapon.

IAEA-held information suggests that Iran may have done experiments to determine the uniformity of implosion necessary for a nuclear weapon in a chamber housed at the Parchin military facility. This is the basis for the IAEA's request to visit the facility. Overhead photos show that the Iranians have been extensively changing the contours of the earth around the building and remodelling the building itself.

Iran's nuclear program includes everything that could be needed for development of an independent civilian power industry. But some of the components could be used for nuclear weapons development, and there is evidence that Iran has, in the past, moved in that direction. We do not know whether that development has continued.

The evidence available to those of us outside the IAEA and the intelligence services is thin and second-hand. It's hard to know Iran's intentions. If they want a bomb, they are not rushing toward one. Some of their actions may be an effort to increase their leverage in the ongoing negotiations. We just don't know enough to say definitively.

Cheryl Rofer is CEO of Nuclear Diner, a website on nuclear issues. She worked at the Los Alamos National Laboratory for 35 years.