Via Foreign Policy:
The latest chess match between Iran and six major powers in Baghdad ended last week without any declared breakthrough. This is not entirely surprising. Talks were unlikely to make significant headway with Iran offering to sacrifice a pawn — 20 percent enriched uranium — in exchange for the queen — the lifting of oil sanctions. Negotiations are scheduled to continue, with a new round set for Moscow in mid-June. But pressures are also building up, which risks a confrontation instead of a settlement.
In the meantime, the International Atomic Energy Agency’s (IAEA) report on Iran, released May 25, reveals new information, most notably the presence of uranium particles enriched to 27 percent, well above the declared 20 percent enrichment level at the Fordow underground enrichment plant. Right now, the key question that the IAEA is trying to answer is how much uranium was enriched to 27 percent and over what period of time the enrichment took place.
During the enrichment process, rows of centrifuges, known as cascades, produce increasingly higher concentrations of the uranium-235 isotope. It is unclear at this stage whether the higher levels reported represent a technical glitch during the start-up of a cascade (when spikes of higher enrichment can take place), or a sign of something more sinister. The spike could have been caused by an operator who changed the cascade’s operating parameters — in particular the rate at which uranium hexafluoride (UF6) gas is fed into the centrifuges — during the start-up phase or at some other time. Another potential cause is cross-contamination, meaning that the particles originated from elsewhere, such as contaminated equipment. This could indicate unknown enrichment activities in Iran. It could also be a problem in the sample analysis. But the IAEA’s method of duplicating samples taken and testing in multiple laboratories makes this an unlikely explanation. [...]
The monthly production of 3.5 percent UF6 at Natanz has increased from 170 kg in February 2012 to 220 kg 3.5 percent enriched UF6 today, but this can be attributed to the higher number of centrifuges and not to better performance. Either way, the result by the end of this year could be a cumulative inventory of 7.5 tons of low-enriched UF6 — enough for half a dozen nuclear weapons.