Representatives of Western governments on Tuesday called on Iran to explain why it had removed nuclear fuel from its sole nuclear power facility, Reuters reported.
The International Atomic Energy Agency safeguards report issued on Friday stated that Iran in October moved fuel assemblies from the reactor core of its Bushehr facility to a pool for holding spent nuclear fuel. Tehran did not say specifically why it relocated the materials.
"This is not a routine matter or something that's quite ordinary," according to an anonymous high-level source from a Western nation. "So this is of great concern. We need answers."
One envoy in the U.N. nuclear watchdog's home city of Vienna, Austria, added: "It sounds a safety bell and then it potentially sounds a safeguards bell if it is used in a weird way." The official was addressing the potential for nuclear weapon-usable plutonium to be collected through reprocessing of used reactor fuel.
Concerns about Iran's atomic intentions have largely focused on the potential for it to produce weapon-grade material through uranium enrichment.
The long-delayed, Bushehr plant, initiated in the 1970s by Siemens of Germany and led since the 1990s by Russia, has been connected to Iran's energy infrastructure for more than a year.
Iranian officials have said there is no cause for concern on this matter. The fuel move was a "normal technical procedure" as Iran prepares to take over management of Bushehr from Russia, said Ali Asghar Soltanieh, Tehran's envoy to the International Atomic Energy Agency.
"Before the handover of the station to Iranian specialists, the inspection work needs to be completed. ... Nothing unforeseen is happening there," said Iranian Ambassador to Russia Mahmoud Reza Sajjadi.
Iran possesses no facility for recycling nuclear fuel and must send any used material back to Russia, noted Arms Control Association atomic specialist Greg Thielmann.
Still, the used material could be "a long-term proliferation concern, because they would provide material from which fissile material could be derived," he added.
Meanwhile, IAEA Director General Yukiya Amano on Monday said Iran's nuclear operation is a continued cause for concern, but must be addressed through diplomatic means.
"The situation is worrying but it is important to continue to seek a diplomatic solution," Agence France-Presse quoted Amano as saying after a meeting with French President Francois Hollande.
The U.N. nuclear watchdog last week reported that Iran had essentially completed installation of uranium enrichment centrifuges at a subterranean complex near Qum. The number of operational devices could quickly be increased from 700 to roughly 1,400, according to the agency's latest safeguards report on Iran.
While Tehran says it is enriching uranium for energy production and other civilian pursuits, the United States and partner nations worry that ongoing production of higher-enriched material at Qum would pave the way for preparation of weapon-grade uranium with an enrichment level of about 90 percent.
Representatives from Amano's organization are set to meet with Iranian officials next month in hopes of establishing an agreement on the scope of the IAEA probe of Iran's atomic activities. The agency in particular is seeking access to Iran's Parchin armed forces installation, which is suspected of having housed nuclear weapon-related research.
The "current situation is worrying but the declared material and installation facilities are under the IAEA safeguard and we can verify that they stay in a peaceful purpose," Amano said.
He added: "We are going to have a high-level dialogue with Iran on the 13th of December in Tehran. The way to solve this issue is by diplomatic means and we will continue our efforts."
On Tuesday, Amano said agency officials "do not see any effect" from the various economic penalties that have been imposed on Iran over its nuclear work, the Associated Press reported. Uranium enrichment up to 20 percent continues at "a quite constant pace," he noted.
The U.N. Security Council has issued four sanctions resolutions aimed at persuading Tehran to halt uranium enrichment. Those measures have been compounded by sanctions from the United States and a host of other nations. In one high-profile move, the European Union earlier this year enacted a full embargo on Iranian oil.
Tehran on Tuesday played down Amano's worries, AFP reported.
"If the (International Atomic Energy) Agency takes a rational approach in the talks an agreement is reachable ... (even) quickly," Iranian Foreign Ministry spokesman Ramin Mehmanparast told reporters. "If there are worries they can be resolved in technical-legal talks."
The official also rejected the new IAEA report's finding on possible efforts by Iran to eliminate evidence of sensitive nuclear work at Parchin.
"It is not possible to clean up nuclear activities and (nuclear) traces will remain," according to Mehmanparast. "It is not appropriate for the director of the agency to make remarks which the experts consider nontechnical and not legal."
Iran is also expected in the near future to resume nuclear talks with six major governments -- China, France, Germany, Russia, the United Kingdom and the United States.
"We will not allow our nation's rights to peaceful nuclear activities to be limited or barred," the Xinhua News Agency quoted Mehmanparast as saying. He added that "we need state-of-art technology for the advancement of our country, including the important nuclear know- how, which has been recognized as our right by [the Nuclear Nonproliferation Treaty], is used peacefully (in Iran)."
The six nations should take a "rational and logical" stance in order to reach a "principled agreement" with Iran, the official said.