|SEIBERSDORF, Austria — The self-styled "Sherlock Holmeses" of the U.N. nuclear watchdog, now seeking access to a major Iranian base, say they have the capability to find tiny traces of atomic material at a site even if a country were to try to cover it up.
In talks later this month, the International Atomic Energy Agency will once again press Tehran to allow its inspectors to visit Iran's sprawling Parchin military complex. That would enable them to bring back swab samples for thorough checks at the IAEA's high-tech laboratory near Vienna.
Western diplomats have accused Iran of trying to cleanse the Parchin site of possible signs of tests relevant for the development of nuclear weapons, casting doubt on whether U.N. investigators would discover anything even if they could go.
Iran says Parchin, located southeast of the capital Tehran, is a conventional army base. It dismisses allegations that it has carried out atomic bomb research and says its disputed nuclear program is for energy and other peaceful aims only.
Experts say that while it may now be difficult to find any evidence, it would still be possible to locate traces of nuclear materials with equipment that can study particles 10,000 times smaller than a grain of sand.
Tell-tale particles could not be removed completely from a facility where uranium was used, said Stephan Vogt, a senior IAEA official, who emphasized that he was speaking generally and not specifically about Iran or Parchin.
"You cannot get rid of them by cleaning. You cannot dilute them to the extent that we will not be able to pick them up. It is just a matter of time," Vogt, who heads the IAEA's Environmental Sample Laboratory, said.
"We won't find it maybe the first time we go there," he said. But, "the more often we go, the higher the probability that we will pick up (traces) in some corner, at some table, in some plumbing."
Former chief IAEA inspector Olli Heinonen said any attempt by Iran to purge Parchin of clues would make the agency's task considerably harder, but "complete sanitization is very difficult to achieve if nuclear materials were actually used."
Like others at the IAEA's Seibersdorf laboratory complex outside the Austrian capital, Vogt was not authorized to discuss Iran, Syria or any other specific cases which have made the agency a key player in international nuclear diplomacy.
But he made clear his confidence in the sophisticated techniques at the scientists' disposal, including a new $5 million instrument to study tiny particles.
NUCLEAR 'SHERLOCK HOLMES'
Likening the IAEA's investigative work to that of fictional detective Sherlock Holmes, Vogt said: "You are running around, looking for the right spot to sample and then you look for microscopic particles.They can tell you stories."
Installed in a purpose-built building, the Large Geometry Secondary Ion Mass Spectrometer can analyze 100-150 samples per year — up from 30-40 previously — collected around the world by inspectors using small pieces of cotton on surfaces.
"We have a much larger magnifying glass. We see much smaller particles," Vogt said, showing the machine, which occupies a room of its own. It "opens brand new doors into what we can see and what we can interpret."
The IAEA has shown it can find particles even when a country has worked hard to hide them. It picked up tiny traces of enriched uranium at Kalaye Electric in Tehran in 2003, even though Iran had removed equipment and renovated parts of the facility.
But despite the IAEA's insistence that it is a technical organization serving 159 member states, its monitoring of Iran's nuclear program can have geopolitical implications.
It regularly inspects Iran's declared nuclear facilities — including the Natanz and Fordow uranium enrichment sites — but has so far failed to persuade Tehran to enable it to resume a stalled investigation into suspected nuclear weapons research.
In a 10th round of talks since early 2012, an IAEA team led by chief inspector Herman Nackaerts will meet Iranian officials in Vienna May 15 to try to end the deadlock.