Satellite images of an Iranian military facility appear to show trucks and earth-moving vehicles at the site, indicating an attempted cleanup radioactive traces possibly left by tests of a nuclear-weapon trigger, diplomats told The Associated Press on Wednesday.
Two of the diplomats said the crews may be trying to erase evidence of tests of a small experimental neutron device used to set off a nuclear explosion. A third diplomat could not confirm that but said any attempt to trigger a so-called neutron initiator at the Parchin site could only be in the context of trying to develop nuclear arms.
The images, provided to the IAEA by member countries, are recent and constantly updated, said one of the diplomats.
The diplomats are nuclear experts accredited to the International Atomic Energy Agency. All asked for anonymity to discuss sensitive information.
Iran is under growing international pressure over its nuclear program, which it insists is peaceful. Israel has warned that it may resort to a pre-emptive strike against Iran's nuclear facilities to prevent Tehran from obtaining atomic weapons.
The IAEA has already identified the Parchin military site as the location of suspected nuclear weapons-related testing. In a November report, it said it appeared to be the site of experiments with conventional high explosives meant to initiate a nuclear chain reaction.
It did not mention a neutron initiator as part of those tests but in a separate section cited an unnamed member nation as saying Iran may have experimented with a neutron initiator, without going into detail or naming a location for such work.
In contrast, the intelligence information shared with the AP by the two diplomats linked the high-explosives work directly to setting off a neutron initiator at Parchin.
Explaining such a device, the agency's November report said that "if placed in the center of a nuclear core of an implosion-type nuclear device and compressed,(it) could produce a burst of neutrons suitable for initiating a fission chain reaction."
If Iran did try to trigger a neutron initiator, it would harden international suspicions by adding a nuclear component to a suspected string of experiments linked to weapons development that generally have not included radioactive material.
The diplomats said they suspected attempts at sanitization because some of the vehicles at the scene appeared to be haulage trucks and other equipment suited to carting off potentially contaminated soil from the site.
Such cleanups would not be new. Iran razed the Lavizan Shian complex in northern Iran, before allowing IAEA inspectors to visit the suspected repository of military procured equipment that could be used in a nuclear weapons program five years ago. Tehran said the site had been demolished to make way for a park, but inspectors subsequently found traces of uranium enriched to or near the level used in making the core of nuclear warheads.
The Iranians also embarked on an extensive redo at the Kalay-e Electric Co., just west of Tehran, before agency inspectors were given access nine years ago. Although the site was repainted and otherwise sanitized, samples taken from Kalay-e also showed traces of enriched uranium, though at levels substantially below warhead grade.
One official from an IAEA member country with good intelligence on Iran said the Parcin neutron initiator experiments were conducted between 2003 and 2010. Another said any such tests were closer to 2003, adding it was not clear whether they were successful.
The timing is important. U.S. intelligence officials say they generally stand by a 2007 intelligence assessment that asserts Iran stopped comprehensive secret work on developing nuclear arms in 2003. But Britain, France, Germany, Israel and other U.S. allies think such activities have continued past that date, a view shared by the IAEA, which says in recent reports that some isolated and sporadic activities may be ongoing.