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Sunday, April 12, 2015

US 'fact sheet' on Iran omits uranium enriched between 3.67% and 20%

The non-partisan Institute for Science and International Security reports that the United States' 'fact sheet' on the recently concluded 'deal' with Iran undercounts Iran's stock of low enriched uranium.
With about 6,000 IR-1 centrifuges and a stock of 300 kilograms of 3.5 percent LEU hexafluoride and no available near 20 percent LEU hexafluoride, our breakout estimate would have a mean of about 15 months, where the minimum breakout time would be 12 months.  We have used the mean as the best indicator of breakout time and interpret the minimum time as a worst case.  Thus, our estimate of breakout would confirm the United States’ assessment that these limitations satisfy a 12 month breakout criterion.  

However, breakout estimates depend critically on Iran’s usable stock of near 20 percent LEU. For example, if Iran also has an inventory of about 50 kilograms of near 20 percent LEU hexafluoride that it can start inserting into the cascades within the first six months of breaking out, and we assume the same conditions as above, the mean breakout time becomes somewhat more than ten months, with a minimal time of nine months.  As a result, minimizing or ensuring that the near 20 percent LEU stock is unusable in a breakout is a high priority.  How these goals would be achieved in a deal is not explained in the Fact Sheet, nor was it discussed in detail in the briefings. 

In fact, it appears from the Fact Sheets and briefings that Iran’s stock of near 20 percent LEU is not included in the 300 kilogram limit on LEU mentioned above.  This limit appears to be applied only to the 3.67 percent LEU.  Given the size of Iran’s stock of near 20 percent LEU, the lack of discussion about the fate of the near 20 percent LEU is problematic in determining breakout estimates.  The near 20 percent LEU stock, unless largely eliminated or rendered unusable in a breakout, could be an important reserve in reducing the time to produce the first significant quantity of weapon-grade uranium (WGU) and rapidly producing a second significant quantity of WGU. 

Despite the fact that Iran no longer has a stock of near 20 percent LEU in hexafluoride form (UF6), it continues to retain a significant portion of this material in the form of oxide (U3O8) and in scrap and waste.  In total, Iran has a stock of about 228 kilograms (uranium mass) of near 20 percent LEU in various forms.  If all of this material were converted back to hexafluoride form, it would possess the equivalent of about 337 kilograms of near 20 percent LEU hexafluoride.  All of this LEU has been fed into the conversion lines to produce oxide.  Of this original amount, about 162 kilograms (uranium mass) ended up as pure LEU oxide powder.  The rest, or about 65 kilograms (uranium mass) of this LEU, ended up in scrap and waste.   

As of February 2015, of the 162 kilograms of near 20 percent LEU oxide (uranium mass), only 42 kilograms of this enriched material were actually present in Tehran Research Reactor (TRR) fuel plates.  About 72 kilograms near 20 percent LEU (uranium mass) were still in oxide form and slated for production of TRR fuel elements.  

The amount in scrap, waste, and in-process was in total as of February 2015 about 113 kilograms of near 20 percent LEU.  Much of this material is in forms where the LEU could be recovered in a straightforward manner.  . 

One point is clear, if left in Iran, these near 20 percent LEU stocks could significantly affect breakout times, lowering them substantially below 12 months.  To help understand its importance, a rule of thumb is that 50 kilograms of near 20 percent LEU hexafluoride (or about 33 kilograms uranium mass) is equivalent in terms of shortening breakout time to 500 kilograms of 3.5 percent LEU hexafluoride.  So, instead of having just 300 kilograms of 3.5 percent LEU, the additional 50 kilograms of near 20 percent would be equivalent to having a total of 800 kilograms of 3.5 percent LEU hexafluoride.  

Based on the briefings, the United States removes the near 20 percent LEU from its breakout estimates once this material is mixed with aluminum and put into TRR fuel elements.  Its assessment is apparently that recovery of the near 20 percent LEU at that point and its subsequent conversion to uranium hexafluoride would take so long that this LEU could not contribute significantly to a breakout, or at least not to the first significant quantity of weapon-grade uranium.  However, recovery of near 20 percent LEU from fresh fuel can be straightforward and the U.S. evaluation requires greater scrutiny.   

In Iraq’s crash program to a nuclear weapon in 1990-1991, it put in place a capability to recover about 33 kilograms (uranium mass) of safeguarded unirradiated and slightly irradiated highly enriched uranium (HEU) from research reactor fuel.  Based on Iraqi declarations and IAEA Action Team evaluations, which we possess, Iraq covertly installed the necessary equipment at the Tuwaitha nuclear site in four months.  It would have needed about a month to test the equipment with dummy fuel and another five months to recover the HEU from the fuel.  This effort was stopped at the point of testing dummy fuel elements by the Gulf War bombing campaign which started in January 1991.  

Because of its far greater experience with uranium conversion, Iran is likely able to recover unirradiated near 20 percent LEU at a similar or faster rate from TRR fuel elements than Iraq. If Iran were to break out, it would undoubtedly secretly install and test the recovery equipment prior to breakout.  Thus, the Iraqi experience suggests that Iran could be recovering near 20 percent LEU from fresh TRR fuel soon after starting its breakout and recover tens of kilograms within several months.  This recovered LEU could be converted quickly into hexafluoride form in facilities also prepared in secret prior to breakout.  
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