Factbox - Unsolved mystery: Possible military aspects of Iran's atomic past

By Shadia Nasralla VIENNA (Reuters) - As nuclear talks with Iran approach a Tuesday deadline, some Western diplomats say questions about the country's atomic past ought to be resolved before sanctions can be lifted. Although Iran has not broken any terms of a 2013 interim deal, the U.N.'s nuclear agency has repeatedly asked Iran to cooperate faster with its investigation into possible military dimensions of the country's atomic program. Below are the key unanswered questions raised by the IAEA, which mostly refer to activities that took place before 2003. BACKGROUND Iran acquired some enrichment knowledge from Pakistani nuclear engineer Abdul Qadeer Khan, the father of Pakistan's atomic weapons program, who confessed to providing assistance to Libya, Iran and North Korea. Some intelligence also came from a laptop smuggled out of Iran. Iran says all of the alleged evidence is forged and dismisses any charges that it was attempting to develop nuclear weapons. However, the IAEA has said the information it has received on potential military aspects of the program is, overall, credible and that it takes nothing at face value. UNRESOLVED QUESTIONS * Using cover companies for the procurement of dual-use equipment and material usable in a nuclear bomb but with civilian applications as well. This includes high-speed electronic switches, high-speed cameras and radiation measurement equipment. * The acquisition of nuclear material, for example a uranium source for enrichment, and efforts to conceal activities involving such material. * Possession of documents detailing how to convert uranium ore into metal and how to produce hemispherical enriched uranium metallic components which can be used in a bomb. * The development of exploding bridge wire detonators, whose explosion times can be set to a very high degree of precision. Such precision detonators are crucial for timing the explosion of a nuclear weapon. Iran has said it needed such technology for its oil sector, according to diplomats, who also say there is no peaceful application for the degree of precision of this kind of detonator. * Design information for a "multi-point initiation system," technology to synchronize detonators used in some atomic bombs. * Hydrodynamic experiments to assess how specific materials react under high pressure as in a nuclear blast. According to some information given to the IAEA by member states, an explosives chamber for such experiments might have been located at the Parchin complex near Tehran, a military site the agency has repeatedly urged Iran to grant it access to. * Calculations on neutron behavior that the IAEA has said has no clear civilian application. Iran has provided some fresh information on these calculations in recent weeks, but not enough to allow a breakthrough in the probe. * Neutron initiator technology which the IAEA has said "could produce a burst of neutrons suitable for initiating a fission chain reaction," as would be needed for an atomic bomb detonation. * Tests to see whether high-tech detonators worked when triggered remotely from a long distance, also potentially relevant to a nuclear weapon. * Engineering studies into missile payloads and their behavior when launched. The IAEA has described these studies as "highly relevant to a nuclear weapon program." * Work on the development of a firing system that would enable a missile payload to explode both in the air or upon impact. * Indications that all the above mentioned areas were organized by a structured management and command chain under the Ministry of Defense Armed Forces Logistics (MODAFL). For the IAEA's full technical annex on these issues, click on https://www.iaea.org/sites/default/files/gov2011-65.pdf (Reporting By Shadia Nasralla)