Iran has moved almost all its enriched uranium out of underground storage and into plain view. But why?

They were many striking elements in the new International Atomic Energy Agency report on Iran, not least its blunt language on the “possible military dimensions” of the Iranian programme. But the strangest part of it was this:

On 14 February 2010, Iran, in the presence of Agency inspectors, moved approximately 1950 kg of low enriched UF6 from FEP to the PFEP feed station. The Agency inspectors sealed the cylinder containing the material to the feed station.

That means that Iran took 94% of its entire stock of low enriched uranium (LEU) from the huge underground tunnels and chambers of its Fuel Enrichment Plant at Natanz and brought it to the surface, to its Pilot Fuel Enrichment Plant (see satellite picture above), which is currently producing 20% enriched uranium, and which is clearly visible from the air.

This stunning move is both provocative and risky. It is provocative because it signals an intention to enrich its LEU from its current level of purity of 3.5% U-235 up to 20%, which is most of the way, in engineering terms, to making weapons-grade material. [Arms Control Wonk has a good explanation of why in the world of uranium enrichment, 20 is closer to 90 than it is to 3.5]

Even if Iran had the technology to turn the 20% uranium into fuel rods for its medical research reactor in Tehran, it does need two tonnes of LEU. According to ISIS, that much LEU would render about 200kg of 20% uranium. The Tehran Research Reactor needs no more than 18.4 kg annually.

The move is risky because it involves shifting Iran’s crown jewels, its 2-tonne LEU stockpile, from subterranean safety where it was invisible to Israeli air force targeteers, to a clearly defined location that might as well have a bullseye painted on the roof.