Adds Iranian confirmation in grafs 3-4 (first version published at 17:39)
Iran, admitting to technical problems with its nuclear power plant at Bushehr, may have to exchange the facility's entire core, diplomatic sources said Saturday in Vienna, dpa reported.
The diplomats were commenting a day after Iran informed the International Atomic Energy Agency (IAEA) in Vienna that it had encountered problems at the plant, which was scheduled to start producing electricity this month.
Iran's IAEA envoy, Ali-Asqar Soltanieh, told the ISNA news agency that Russian experts have advised Iran to unload the fuel from the reactor core so further tests - including some related to safety - can be undertaken.
Trying to downplay the incident, Soltanieh said that the fuel would be returned to the reactor as soon as the tests are completed.
While the Iranian report to the IAEA apparently did not specify how serious the technical problems were, diplomats said the entire core must be removed and replaced.
The Iranian report had said that all 163 fuel rods would have to be removed from the reactor core. The diplomatic sources said that there were problems with all the fuel rods.
Nuclear power experts noted that smaller problems with nuclear fuel rods are common when starting up a reactor, but that the replacement of the entire core was an issue of a much greater magnitude.
There was also speculation about what had caused the problems in the Russian-designed nuclear facility, which was opened in August 2010, with Russia also supplying the initial 82 tons of nuclear fuel for the plant.
The speculation ranged from the problems caused by the Stuxnet computer worm that had attacked Iran's nuclear programme last year, to suggestions of intentional sabotage by Russia, which has come to have serious doubts about Iran's insistence that its nuclear activities are purely for peaceful purposes.
One high-level diplomat in Vienna who spoke on condition of anonymity said "it isn't our job to speculate about the reasons."
But an expert in Washington, David Albright, said it raised questions about Iran's nuclear know-how.
"This could represent a substantial setback to their programme," Albright, president of the Institute for Science and International Security, told the New York Times newspaper.
"It raises questions of whether Iran can operate a modern nuclear reactor safely," he said.
"The stakes are very high. You can have a Chernobyl-style accident with this kind of reactor, and there's lots of questions about that possibility in the region," Albright added, referring to the April 1986 nuclear plant meltdown at Chernobyl, in the Ukraine.