For Iran, Enriching Uranium Only Gets Easier

[steven johnson]

Purification of weapons grade uranium is apparently easier as the process goes along.

In the Iranian desert, at a sprawling industrial site ringed by barbed wire and antiaircraft guns, a shift in the enrichment of uranium is producing global jitters because it could shorten Iran’s path to the acquisition of nuclear weapons.

It is also illustrating one of the peculiarities of uranium enrichment, a version of the rich getting richer, really fast. The tricky process accelerates as it moves ahead. “The higher the concentration, the easier it gets,” said Houston G. Wood III, a professor of mechanical and aerospace engineering at the University of Virginia who specializes in nuclear enrichment. The process is, as scientists like to say, nonlinear.

Four years ago, Iran began enriching uranium on an industrial scale with centrifuges, machines that spin extraordinarily fast to separate uranium 235 from the more common form of the element, uranium 238. Uranium 235 is a natural rarity that splits easily in two, or fissions, in bursts of atomic energy, either in a reactor or a bomb. Reactor-grade fuel is usually defined as uranium 235 of about 4 or 5 percent, and bomb-grade as 90 percent or higher.

A practical illustration of nonlinearity is that Iran — or any other nuclear hopeful — needs increasingly few centrifuges to make uranium 235 increasingly potent. For instance, one industry blueprint features 3,936 centrifuges for enriching up to 4 percent, 1,312 centrifuges to 20 percent, 546 centrifuges to 60 percent and just 128 centrifuges to 90 percent — the level needed for a bomb.


For Iran, Enriching Uranium Only Gets Easier