West aims to minimise nuclear bomb risk

DIPLOMATIC PHASE

In the new diplomatic phase, which has to finish in July or the six-month interim accord may have to be renegotiated, both sides must satisfy hardliners at home.

In a foretaste of difficulties ahead, Iranian Foreign Minister Mohammad Javad Zarif clashed with US negotiator Wendy Sherman this month over the future of Iran's planned Arak heavy water reactor and the Fordow underground enrichment site.

Western states worry Arak, likely to be at the heart of the talks, could yield plutonium for a bomb. Sherman suggested Iran had no need for it or for Fordow. Zarif called her comments "worthless" and said atomic technology was non-negotiable.

Israel, which views a nuclear-armed Iran as an existential threat, will push the six negotiating powers - the United States, Russia, China, France, Britain and Germany - to demand that Iran gives up Arak as well as its enrichment plants.

Iran says it is Israel, with its assumed atomic arsenal, that threatens regional peace and security.

Negotiators say one possible way forward on Arak could be to modify it so that it can still produce medical isotopes, Iran's stated goal, without using heavy water which provides a potential route for obtaining weapons-grade plutonium.

Another major issue will be the number of centrifuges - machines that spin at supersonic speed to refine uranium - that Iran is allowed to keep. Enriched uranium can have both civilian and military uses.

Jofi Joseph, former director for non-proliferation on the White House National Security Council staff, said Iran will likely demand it can keep 10,000 machines in operation. It has nearly the same number installed but not running.

But nuclear experts say Iran must sharply reduce its centrifuges in order to extend the time for producing enough weapons-grade fissile material for a bomb. Iran says it only refines uranium for a planned network of nuclear power plants.

"The number and type of centrifuges will be limited to ensure that breakout times are ... a minimum of six to twelve months at all times," the Institute for Science and International Security (ISIS), a US-based think-tank, said.

"In the case of a six-month breakout time, Iran should have in total no more than 4,000 IR-1 centrifuges," it said, referring to the old-generation equipment Iran has. It is also testing more modern machines, another bone of contention.

The two sides want the final-phase talks to last no more than half a year, and be finished by the time the interim deal expires on July 20. Many experts believe that is unrealistic.