U.N. nuclear inspectors revisiting an Iranian laboratory to follow up on activities that could be linked to a secret nuclear weapons program recently discovered that some equipment believed used in the experiments has disappeared, diplomats said Friday.
One of the diplomats told The Associated Press that senior officials within the International Atomic Energy Agency _ the U.N. nuclear watchdog _ were concerned that the removal was an attempted cover-up.
Two others confirmed that some apparatus had gone missing. One said it was too early to draw conclusions, suggesting it could have been taken to another site for nothing more than maintenance. The three spoke on condition of anonymity because information surrounding the Iran nuclear probe is confidential.
At issue is pyroprocessing, a procedure that can be used to purify uranium metal used in nuclear warheads.
Iran in January confirmed to the agency that it had carried out pyroprocessing experiments, prompting a request from the nuclear agency for more information _ but then backtracked in March in comments at a closed meeting of the IAEA's governing board.
"In fact there is not pyroprocessing R&D activity and the question raised has been a misinterpretation by the Agency inspectors," said an excerpt of the Iranian statement made available this week to the AP.
The experiments prompted IAEA experts to revisit the site _ the Jabr Inb Jayan Multipurpose Research Laboratory in Tehran _ where they found some of the equipment removed to an undisclosed site, said the diplomats. One of the two said the electrolysis unit used in separating out impurities from uranium metal was among the apparatus that had been removed. Another said chemical apparatus used in the process were now missing.
IAEA officials said the agency would have no comment. Attempts to get Iranian comment were not immediately successful, with Vienna-based Iranian officials not answering their cell phones.
Any Iranian pyroprocessing work, even on an experimental basis, would add to suspicions that Tehran is interested in developing nuclear weapons _ even though it insists it is solely interested in the atom as an energy source.
The U.N. Security Council is currently considering a fourth set of sanctions in response to the Islamic Republic's refusal to halt uranium enrichment _ which can create both nuclear fuel and the fissile core of warheads. It is also concerned about Tehran's belated revelation earlier this year of a secret enrichment site under construction and its refusal to answer IAEA questions based on foreign intelligence and linked to suspicions of hidden nuclear weapons work.
South Korea and the United States are currently experimenting with another nuclear use for pyroprocessing, which reprocesses spent nuclear fuel for a new breed of reactors. But this procedure is highly technical and does not match the nuclear profile of Iran, which does not have any used fuel to reprocess.
One of the diplomats said the issue of missing equipment might figure in the next Iran report of IAEA chief Yukiya Amano, due later this week or early next week for review by the IAEA board starting June 7.
Other than that, the report is unlikely to break new ground, noting that Iran's low enrichment program is stagnating, and that Iran continues a pilot program of enriching to higher levels, near 20 percent, he said.
Iran originally justified its decision to start enriching to higher levels by saying it needed the material to fuel its research reactor after a deal to secure such fuel from abroad fell apart.
Earlier this week, it submitted a new plan to the IAEA that foresees Tehran swapping some of its low-enriched uranium for reactor fuel _ terms similar to an earlier plan drawn up in October.
On its face, the latest plan seems a significant concession, with Iran agreeing to ship 1,200 kilograms (2,640 pounds) to be stored in Turkey and to wait up to a year for higher-enriched uranium from France and Russia. However, Iran is believed to have much more nuclear material stockpiled now.
In October, such a swap would have left Iran with much less than the 1,000 kilograms (2,200 pounds) of material needed to produce enough weapons-grade uranium for a bomb. Since then, Iran has continued to churn out low-enriched material, along with starting to enrich to near 20 percent.
In March, the IAEA said Iran's stockpile stood at around 2,100 kilograms (4,600 pounds). It has likely grown to an estimated 2,300 kilograms _ about 5,000 pounds, or more than twice the amount needed to produce enough material for a bomb, according to David Albright of the Washington-based Institute for Science and International Security, which has tracked Iran for signs of covert proliferation.
From the West's point of view, that destroys much of the incentive for an agreement. And Iran's decision to continue its program to enrich to near 20 percent _ whether or not it gets fuel from abroad _ poses an even greater hurdle because it brings Tehran closer to weapons capability.