Has Iran initiated a slow motion breakout to a nuclear weapon?

by David Albright, Paul Brannan, and Andrea Stricker

July 12, 2010

by David Albright, Paul Brannan, and Andrea Stricker

Ali Akbar Salehi, head of the Atomic Energy Organization of Iran, announced today that Iran intends on producing 120 kilograms of 19.75 percent uranium by September 2011, purportedly for use in the Tehran Research Reactor (TRR). Salehi also announced that Iran is working on producing fuel plates. This announcement raises concern that Iran is conducting a “slow motion breakout,” and that it could seek to make larger quantities of 19.75 percent enriched uranium as a way of bringing it closer to producing weapon-grade uranium for nuclear weapons.

Last month, ISIS released a report examining Iran’s production of 19.75 percent uranium and estimated that Iran would need between 125 kilograms and 210 kilograms of 19.75 percent uranium feedstock to further enrich up to weapon-grade in sufficient quantity for one nuclear weapon. The range reflects the amount of weapon-grade uranium needed in a nuclear weapon. The estimate assumed that the final tails assay would be 0.7 percent, or the level of natural uranium, based on Iran’s statements about taking the tails enriched to 2 percent from the cascade producing 19.75 percent low enriched uranium (LEU) and feeding them into a second cascade, where the final tails assay of this second cascade would be 0.7 percent. ISIS further estimated that it would take at least 2.5 years to make 125 kilograms of 19.75 percent uranium using one cascade at the Pilot Fuel Enrichment Plant (PFEP), and between 1.25 and 2.5 years using two cascades. Iran may need to use more than one cascade to meet its goal of 120 kilograms of 19.75 percent LEU by September 2011.

Although Iran states that it intends to use the 19.75 percent LEU in the production of TRR fuel elements, if Iran stockpiles this amount of 19.75 percent enriched uranium, it could have nearly the amount needed to produce subsequently enough weapon-grade uranium for a bomb. Once it has enough 19.75 percent LEU, it is 90 percent of the way to weapon-grade uranium, meaning Iran could go from 19.75 percent to 90 percent in as little as one-tenth the time needed to go from natural uranium to weapon-grade uranium.

Iran could continue producing more 19.75 percent LEU once it reaches that initial September 2011 target of 120 kilograms. Iran could also cite this goal as the basis for enriching up to 19.75 percent in an increasing number of cascades and eventually surpass its target quantity.

Reducing Feed Requirements in a Breakout

Based on its own statements, Iran appears to be implementing a way to more efficiently use the tails and reduce the amount of 3.5 percent LEU feed it requires. Instead of storing the 2 percent enriched tails, it has stated it will further enrich them in a second cascade, in a recycling process. The final tails would be 0.7 percent and reusable in the cascades that make 3.5 percent LEU. Iran did not state the enrichment level of the product of this second cascade, but it may be only 3.5 percent, meaning it would feed the 2 percent LEU into the upper stages of the second cascade. Iran could then feed this 3.5 percent LEU into the first cascade to make more 19.75 percent LEU and start the whole process again. By doing so, Iran could significantly reduce the amount of 3.5 percent LEU feed needed to make 19.75 percent material.

Such recycling would be particularly useful to a state attempting breakout with limited amounts of enriched uranium. For example, without recycling, Iran might need about 2,000 kilograms of 3.5 percent LEU to produce 25 kilograms of weapon-grade uranium, where weapon-grade is achieved in three steps. But by simultaneously enriching the tails in other cascades (and reducing the tails in those parallel cascades), Iran could reduce by half the amount of 3.5 percent LEU it would need to produce 25 kilograms of weapon-grade uranium. Although this recycling would require Iran to dedicate more centrifuge cascades to a breakout, it would allow for a smaller initial stock of 3.5 percent enriched LEU.


The United Nations Security Council has called on Iran to suspend its enrichment program, and Salehi’s announcement further confirms the necessity of achieving this goal. As a step to a suspension and a way to build confidence in negotiations, the LEU fuel swap deal remains important.

Salehi claims in today’s statement that Iran is “now producing fuel plates.” This is likely an exaggeration of Iran’s capabilities. Today’s statement demonstrates that Iran continues to make increasing amounts of 19.75 percent enriched uranium, but it still likely lacks the ability to manufacture fuel for the TRR. This paradox indicates that there is still time for an LEU fuel swap deal, where Iran halts further production of 19.75 percent LEU and sends this material out of the country with 3.5 percent LEU. This deal would be in Iran’s interest if it intends on fueling the TRR in September of next year.

email us twitter share on facebook