Enriching uranium more than a matter of spin

The Times : Iran’s announcement that it has started running 164 centrifuges in Natanz still leaves it a big step away from being able to make weapons (although it denies that that is its aim). The Times

By Bronwen Maddox

IRAN’S announcement that it has started running 164 centrifuges in Natanz still leaves it a big step away from being able to make weapons (although it denies that that is its aim).

Running a cascade, or linked chain, of centrifuges reliably is the most difficult obstacle to making a bomb. The cylinders, made of hardened steel, must spin fast, day and night, for months without wobbling or crashing.

“I’m a bit sceptical that they can run the cascade continuously,” Mark Fitzpatrick, a proliferation specialist at the International Institute for Strategic Studies in London, said. “They would have to do that for several months to be confident they had overcome the hurdles.”

In the enrichment process, uranium in a gaseous form is fed in at one end of the line of centrifuges and extracted at the other. The spinning separates the rarer form of uranium, U-235, which is needed to sustain a nuclear reaction in the core of a reactor, or to create an explosion. The concentration, or enrichment, of the U-235 increases as it passes through more centrifuges. If it is not enriched enough, it can be returned to the start.

A power plant needs uranium enriched to 3 per cent. Weapons-grade uranium is at least 80 per cent. But those figures are misleading. “Half the work is done in getting to 3 per cent,” Mr Fitzpatrick said. It would take only the same effort again to produce weapons-grade material.

How long that takes depends on the number of centrifuges. A cascade of 164 machines is a pilot plant. It represents a big step forward; previously, Iran had managed to link only a dozen or so. But even 164 is tiny. Using that cascade it would take 13 to 17 years to make the 20kg to 25kg (44lb to 55lb) of highly enriched uranium needed for a weapon.

Iran has said that it plans to build an industrial-scale plant of 50,000 centrifuges at Nat- anz. In theory this could produce material for a bomb in weeks. But constructing the plant — acquiring components for centrifuges or making and testing them — is a huge undertaking.

Gary Samore, of the MacArthur Foundation in Chicago, and a specialist in the Iranian nuclear programme, says that Iran might well want to avoid the confrontation with the UN that a huge centrifuge plant would bring. But with a small cascade, it could build up a stockpile of low- enriched uranium, he said. That would give it “a much quicker breakout capability” if it chose to make the dash for a weapon.