STEVE INSKEEP, Host:
Iran and six world powers gather in Istanbul tomorrow for a new round of nuclear talks. Iran continues to insist it is not seeking nuclear weapons and that its nuclear rights, including the right to enrich uranium, are not up for discussion. NPR's Istanbul correspondent Peter Kenyon recently visited Vienna, home of the International Atomic Energy Agency. He has this report on what Iran has done - and not done - to worry nuclear experts.
PETER KENYON: Here are a few examples. For several years, the IAEA has known that Iran was working with laser-based uranium enrichment. Former IAEA Director General, Pierre Goldschmidt, says Iran's interest in this cutting-edge technology raised a number of questions.
PIERRE GOLDSCHMIDT: Laser uranium enrichment technology is one of the most difficult and sophisticated enrichment technology. So far it had no industrial or commercial application.
KENYON: Goldschmidt says the site at Lashkar Abad where this technology was apparently used was shut down by the Iranians. But that didn't answer one key question: what was Iran enriching the uranium for?
GOLDSCHMIDT: The agency determined - and this is all public information - that they had this enrichment facility, and that some part of the design of the equipments were relevant for the production of high-enriched uranium.
KENYON: Highly enriched uranium is not necessary for nuclear energy production, but is highly desirable for nuclear weapons. Iran says enrichment is its right, no matter what technique it may choose. But this gets to a key problem for the IAEA - it only sees what Iran lets it see. Some of the most dramatic discoveries have come from international intelligence or Iranian opposition groups. The revelation of a previously secret enrichment plant near the city of Qom in 2009 is a case in point. Another example: A few years ago, the agency learned of a 15-page document Iran had received that discussed converting uranium gas into uranium metal hemispheres. A process that experts say could be part of designing a nuclear weapon. Former IAEA inspector, Ollie Heinonen, now at Harvard's Kennedy School of Government, says at that point, the questions became more serious.
OLLIE HEINONEN: Why would you have such kind of document? Well, Iran said that they got it without asking. But the fact is that the document is there, it came from Pakistan, that's clear. And the both of them acknowledge that this is to do with the nuclear weapon design.
KENYON: The agency has also confronted Iran with information suggesting that Iran had been involved in high-explosive testing and other activity relevant to nuclear weapon research and design. Iran said some of the testing was for conventional weapons only, and dismissed other allegations as a disinformation campaign by its enemies. Heinonen says the only way to put these suspicions to rest is to have a thorough and open discussion between Iran's nuclear experts and the I.A.E.A. But he says for the negotiators coming to Istanbul, getting to that point is probably too much to ask out of this two day session.
HEINONEN: Well, I think that still people are now testing waters. But they are talking and I hope that now after this round people start to get closer and look at what needs to be done. It has to be a cooperative effort. It has to be also, you know, attractive to the Iranian side, so I hope that someone has the magic formula.
KENYON: Peter Kenyon, NPR News, Istanbul.