Mark HibbsReconverting Iran’s U3O8 to UF6

What do we really know about Iran’s capability to reconvert triuranium octoxide (U3O8) enriched to 20% U-235 back into UF6 feedstock that can be further enriched to produce weapon-grade uranium? Can Iran do it? And if so, how fast?

The answer matters considerably, as Iran, Israel, and the P5+1 will make decisions this year, based in part on their assessment of risk, about the fate of current efforts to negotiate a comprehensive crisis settlement.

In the policy world, there are two opposing views being expressed, whether they are informed by the facts on the ground in Iran–or not.

Advocates of stepped-up diplomacy with Iran argue that Iran, by not accumulating 20%-enriched EUP from the Fordo enrichment plant as UF6 but instead converting some of it to U3O8, is signaling to the powers its willingness to compromise and de-escalate the crisis. In U3O8 form, they argue, the material would be less directly usable should Iran want to dash to a bomb, because Iran would have difficulty reconverting the oxide to UF6, especially if the oxide had been fabricated into finished research-reactor fuel.

Iran’s determined adversaries assert to the contrary that there is no nonproliferation benefit in Iran converting its 20%-enriched Fordo output to U3O8 because Iran could reconvert the material back to UF6 easily and in a hurry.

Iran has described its converting of the UF6 into U3O8 as a confidence-building measure.

U3O8 and Israel’s ‘Red Line’

This week, a former Israeli intelligence official claimed that Iran could within a few days reconvert its U3O8 back to UF6, implying that Iran has already crossed a “red line” set by Israeli Prime Minister Benjamin Netanyahu–the production of enough 20%-enriched uranium which could be enriched to weapon-grade and fashioned into a nuclear weapon. Three days later, in a Reuters interview alerting the outside world it is prepared to continue talking with the P5+1, an Iranian negotiator made known that Iran intends to continue converting the Fordo product to U3O8 for use as fuel for five research reactors. These reactors presumably would include the existing Tehran Research Reactor (TRR) plus four more reactors that, according to Iranian press reports  in 2012, Iran’s President Mahmoud Ahmedinejad had ordered to be built. Whether or not Iran ever builds those four reactors, they provide Iran a rationale to continue enriching uranium to 20% and converting the EUP to U3O8. There is also the research reactor at Arak, but it will not require 20%-enriched uranium to operate when it is finished.

As of late February, the last time when the IAEA reported to the Board of Governors on safeguards implementation in Iran, the status of Iran’s inventory of 20%-enriched uranium produced at Fordo was this, as I described in a post earlier this month:

After commencing with the enrichment of uranium to 20% U-235 in early 2010, Iran accumulated about 150 kilograms of EUP at this enrichment by the end of 2011, and it crossed the 200 kg threshold sometime in the middle of 2012.  The latest report from the IAEA in February says that Iran had produced 280 kg of UF6 enriched to 20% U-235, of which 167  kg was still in the form of UF6. Virtually all of the rest has been introduced into the reconversion plant to produce U3O8 for fuel fabrication. When the IAEA accounted for Iran’s declared activities in February, the plant had produced U3O8 containing 50 kg of uranium, leaving about 60 kg of uranium in the process inventory. According to the IAEA data, the current rate of production of feedstock at this enrichment level in its centrifuges is about 15 kg per month.  

By late February, then, Iran had processed about 110 kg of its accumulated UF6 inventory enriched to 20% into U3O8 and other intermediary chemical states. At current rates of production at the Fordo enrichment plant and chemical processing facilities at Esfahan, by the end of this year Iran might accumulate a U3O8 inventory containing approximately 175 kg U enriched to 20% U-235–but only if it is assumed that all the uranium fed into the conversion line would be converted to U3O8. Data from the February IAEA report suggest that the real conversion factor from UF6 to U3O8 is far less.

According to Susan Voss based on data in IAEA reports on Iran’s safeguards implementation Iran has lost 61% of its uranium in feed material during the conversion of UF6 to U3O8 for the TRR.

Olli Heinonen however believes Iran’s present conversion factor is higher.

The IAEA reports provide the amount of UF6 moved (and “released”, which means the cutting of the IAEA seals from the UF6 cylinders) to [Iran’s Fuel Plate Fabrication Plant] but it does not give a full breakdown for material in each step of the process. The reports give the amount of U3O8 produced at certain point of time, which is just one part of the material balance equation. There are all the reasons to believe that the Iranian engineers, with two decades of experience on uranium conversion, can achieve a better yield than 39 %. In addition, 20 % enriched uranium is valuable material. Like the other fuel producers, [Iran has] a small process, at least on the drawing board, to recover uranium from the wastes (albeit only a few per cent of material should end up in wastes).


In a statement before the Institute for National Security Studies in Tel Aviv on April 22, Amos Yadlin, former head of Israel’s Military Intelligence  Directorate, asserted that Iran in “less than a week” could convert its 20%-enriched U3O8 into bomb-grade “nuclear material” for a weapon.

In separate comments made to Israeli radio, Yadlin appeared to suggest that right now 80 kg had been processed into U3O8 and was therefore available to be reconverted to UF6.

Iran’s Capabilities and Options

We may assume that Yadlin’s remarks in some quarters will be interpreted to drive a stake into the heart of any forthcoming compromise deal with Iran, challenging those who argue that Iran has demonstrated self-restraint in not stockpiling 20%-enriched UF6. Iran’s capabilities for reconverting the 20%-enriched U3O8 back into UF6 feedstock for nuclear weapons fuel therefore need to be understood and the following questions need to be answered: 

Does Iran now have the means to reconvert its U3O8 to UF6?

Yes. Do not be confused by the terms conversion and reconversion. I have heard it said: “Iran can convert the Fordo enriched uranium from UF6 to oxide but it cannot reconvert the oxide back to UF6.” Not true. The chemical processes corresponding to “conversion” and “reconversion” are more or less identical. Iran has lots of experience converting its uranium ore concentrates to UF6, and Iran can likewise convert U3O8 obtained from UF6 back into UF6. In both cases, the feedstock for conversion is U3O8. In the first instance, it is milled from natural uranium ore. In the second, the feedstock is oxide that has been converted back from UF6 which was previously enriched.

How would Iran process its U3O8 into UF6?

Iran would have a number of options, but there are two basic ones.  They principally differ in how to convert U3O8 to the intermediate product UO2. To convert the UO2 to UF6, the process would be the same for both options.

One option would be to reconvert U3O8 into UO2 using a process similar or identical to that used at Iran’s Uranium Conversion Facility (UCF) at Esfahan, which Iran has operated to produce its UF6 feedstock for centrifuge plants at Natanz and Fordo. The U3O8 would be dissolved in nitric acid, producing an aqueous solution of uranyl nitrate hexahydrate [UO2(NO3)2 . 6H2O]. In some versions, this would then be mixed with tributyl phosphate to remove the uranium in the form of uranyl nitrate. The nitrate can be converted to UO3 either by evaporation or treatment with ammonia. The UO3 is in turn converted to UO2 in fluidized reactors by reduction with ammonia gas at high temperatures.

A second option would be a dry process to expose the U3O8 to very high temperatures in the presence of hydrogen gas. The endothermic reaction of U3O8 with H2 would result in UO2 and water. It is likely that Iran has studied and may have mastered this kind of process at laboratory scale. If Iran has mastered it, less time may be required to reconvert the U3O8 than by using a wet process, because fewer steps would be needed. Iran might favor a dry process route because its enriched U3O8 contains few or no impurities, obviating the need to do solvent extraction. The impurities, such as oxidizing metals, would have been already removed at UCF prior to enrichment of the NATU at Fordo.

For both wet and dry options, after the material is converted to UO2, it would be reacted with anhydrous hydrogen fluoride (AHF) to produce UF4, and the UF4 would in turn be fluorinated to result in UF6.

Iran has investigated several process chemical options for doing this since the 1980s. Most of the processes have been applied elsewhere in the world, and in all the nuclear weapon states, beginning in the 1940s, and they are well-known.  In addition to experience gained at UCF since the mid-2000s, Iran a decade before operated a small chemical conversion lab to produce UF6, and Iranian scientists have also worked on uranium conversion chemistry in its so-called “Green Salt Project.”

Where would Iran do the U3O8-UF6 reconversion?

In theory, Iran could use its existing and declared conversion infrastructure at Esfahan to convert the U3O8 beginning with nitric acid dissolution and ending with production of UF6 gas. In practice, because any re-conversion in a safeguarded facility of a discrete inventory of previously enriched U3O8 would, if detected or declared, prompt IAEA inspectors’ concerns (the UCF is routinely monitored), reconversion would more likely take place in an undeclared facility dedicated to process enriched U3O8.

Should Iran choose to reconvert the U3O8, it would have other motivations to do it in a dedicated, small installation. The geometries of such a facility could be designed to minimize the risk of a criticality accident, which could occur during the processing of 20%-enriched feedstock. At a bulk-handling facility such as UCF, designed to process NATU, criticality management would be more challenging, and the risk of an accident, especially if enriched uranium were converted under duress, would be greater. The kind of issues Iran would face are illustrated here.

A small facility would be best to permit batch processing, allowing personnel to most effectively control off-gas and ventilation systems needed to cope with volatile hydrogen and fluorine gases involved in the conversion of UO2 to UF6. Iran might use a fairly simple process, similar to that used at the JCO fuel processing plant in Japan, which in 1999 suffered a criticality accident when buckets filled with uranium solutions were carelessly handled by personnel.

How much time would Iran require to reconvert the enriched U3O8 to UF6?

Yadlin, cited as having told the Institute for National Security Studies that in Iran the reconversion of U3O8 to produce bomb fuel could be “completed in less than a week,” walked back this estimate in a subsequent radio interview to “between one and two weeks.” That’s more realistic. Experience from the uranium conversion industry and R&D sector outside Iran would suggest that Iran might be able to convert about 100 kg of U3O8 to UF6 in about two weeks–provided, however, that the work was carried out in a small facility using a dry process without purification, whereby perhaps three batches would be consecutively processed. Use of other processes and a larger installation might lengthen the time required to reconvert the material. Regardless of whether Iran would select a wet or dry process, the most time-critical process step would likely be the production of UF4 from UO2 because of the comparatively slow reaction time for AHF and UO2.

The IAEA Safeguards Glossary includes a table for estimated material conversion times to produce finished nuclear weapon metal fuel components using various fissile material feedstocks. Conversion time is defined as:

the time required to convert different forms of nuclear material to the metallic components of a nuclear explosive device. Conversion time does not include the time required to transport diverted material to the conversion facility or to assemble the device, or any subsequent period. The diversion activity is assumed to be part of a planned sequence of actions chosen to give a high probability of success in manufacturing one or more nuclear explosive devices with minimal risk of discovery until at least one such device is manufactured.

For “U-233 oxide and other pure U compounds,” the conversion time is given by the IAEA as “order of weeks (1-3).” A footnote specifies that for pure compounds it would be closer to one week and for “mixtures and scrap” material it would be closer to 3 weeks. This implies that to avoid detection a determined proliferator should take no more than three weeks to process pure uranium oxide into finished metal components.


If Iran processes its 20%-enriched U3O8 into fuel for the TRR–which Iran says it is doing and IAEA reports have verified–wouldn’t that serve as an effective proliferation barrier?

If Iran uses 20%-enriched U3O8 to make fuel for the TRR, converting that fuel material back to UF6 might require just a few more days than is needed to reconvert U3O8 powder.

The fuel for TRR consists of aluminum plates containing U3O8-Al fuel in a matrix. Iran would probably make this fuel using hot presses to bind the fuel material and the aluminum. To get at the U3O8 after fuel is fabricated but not yet irradiated, Iran could dissolve the fuel in a stainless steel vessel containing a caustic solution like sodium hydroxide, filter the mixture, and then dry and recover the oxide. Iran would have to be careful in handling the large amount of hydrogen gas that would be generated by dissolving the fuel.

Were the U3O8 to be fabricated instead into ceramic fuel using a sintering process for other reactor types, that fuel would be more difficult to break down and dissolve and it would potentially take longer to react with fluorine. Were Iran at some point in the future to make a deal with foreign governments and fuel suppliers including the supply TRR-type fuel, the proliferation barrier against diversion of enriched fresh fuel would be strengthened if silicide fuel were required instead of U3O8-Al fuel, because the silicide would be more difficult to dissolve.

The Bottom Line

Iran could process its entire inventory of 20%-enriched U3O8 to produce UF6 in a matter of a few weeks, the fruit of Iran’s cumulative nuclear chemistry R&D and industrial-scale experience over three decades. There are uncertainties about how great Iran’s production losses would be should it decide to reconvert the material.

An inventory of 20%-enriched uranium in Iran consisting of U3O8 reconverted from output from the safefguarded Fordo enrichment plant would be under IAEA safeguards. If it were associated with the UCF, it would be subject to physical inventory verification (PIV); if collected in small containers, it would likely be put under seal. The conversion of a portion of Iran’s U3O8 inventory into UF6 and subsequent re-enrichment could in theory be built into any of a number of break-out scenarios. How Iran would in fact behave can only be a matter of conjecture. Were Iran to inform the IAEA it intended to remove seals or reconvert the material into UF6, that step would immediately precipitate a crisis. If Iran were ever to decide to divert safeguarded enriched uranium to make a nuclear explosive device,  in addition to the risks of detection which would pertain to that action,  it would have to consider whether there would be any advantage in reconverting any of the U3O8 to UF6.


  1. SQ (History)

    You’ve done some impressive homework here, Mark. I was going to ask about irradiation, but it doesn’t sound like the bulk of the material will be made into fuel and irradiated. At the rate Iran is going, they’ll have material enough to fuel five reactors before long, only one of which exists.

    Still, fuel fabrication alone would be beneficial from a confidence-building perspective. That’s another step that must be reversed before re-enrichment could take place.

    In the meantime, your last paragraph says it all — the enriched material is under containment and surveillance. Breaking that C&S precipitates the crisis. The detailed timeline beyond that point is not necessarily so crucial.

  2. mark (History)


    I decided to spare readers any more details about this and omitted considerations of irradiated fuel.

    [See Olli Heinonen’s comment below concerning the irradiation of TRR elements. One handmade element, he reports, is now being irradiated in the TRR].

    In the world of research reactors, in general there are exacting QA requirements involved in powder sorting and getting uniform particle distribution for this type of fuel.

    No question that trying to recover any U3O8 from irradiated RR fuel would take a lot of time and must involve work in a hot cell. I doubt extremely Iran or anyone else would be tempted to consider this if there were other routes to securing enriched UF6 feedstock, to say nothing of the considerations about uranium isotopic purity and neutron poisoning (since we’re talking about fuel for an explosive device) that would arise in irradiated material.

  3. Jay (History)


    Your “bottom line” is fairly accurate. And, although I agree with the hypothetical possibility outlined in the rest of your narrative, I must say that the scenario is highly improbable. With increasing rate of ore production and conversion by Iran, and other potential means of “going nuclear”, the modality of reconversion seems like a red herring! In other words, they are very close to the threshold capability, and from that point it is merely a decision for Iran with multiple routes to get there – reconversion being one, but a much less efficient, more obvious, and less probable one.

    • mark (History)


      Your comment is the perfect opportunity for me to underscore that nowhere in this post do I express a point of view about whether Iran would or would not take a decision to reconvert the material for whatever purpose whatsover.

      The reason I investigated this in detail was to throw light on a subject about which a number of people have already expressed very strong views concerning Iran’s capabilities in the field of chemical processing of uranium.

      All are free to have and express their opinions about what Iran is capable of doing. But these are the facts to the extent which I could determine them.

      Iran and its scientists have capabilities which no one can take away from them. Most of us want Iran to stay in the NPT and not making nuclear weapons based on what their capabilities are. Beyond that, as my colleague Pierre Goldschmidt says, “tout le reste est littérature.”

  4. Jay (History)


    Thanks for the reply. Fair enough!

    Without taking a position on what Iran would or would not do, I wanted to highlight the potential that hypotheticals without context could get in the way of fruitful negotiations, and that we should focus more on the fact that even small confidence building measures are steps in the right direction.

    • mark (History)


      There is a debate in some quarters about whether Iran is holding back on the accumulation of its 20%-enriched UF6 inventory at Fordo because it fears an Israeli attack, where some people suggest that Iran may be converting the material to U3O8 because Iran is respecting Israel’s “red line.” Iran’s view, and the view of many supporters of active diplomacy, is that converting the material to U3O8 should be seen as a CBM.

      I was motivated to get into this because in some cases Iranian apologists as well as Iran’s adversaries were making what appeared to be convenient and perhaps unfounded assumptions about Iran’s capabilities in this area.

      That being said, what you write about the value of CMBs is valid. It’s up to Iran and the P5+1 to move that process forward. They don’t seem to be doing very well. If Iran’s conversion of the UF6 into oxide is an opportunity, then so far the seven parties to this negotiation haven’t taken advantage of it.

  5. Anon2 (History)

    Last time I did rough SWP calculations for Fordow, I figured that using all the centrifuges would take 2 additional weeks to enrich from 20% to weapons grade.

    Was that extra enrichment time included in this 20% U308 reconversion breakout timeline?

    Finally, poisoning (irradiating) the U308 in the TRR would be a confidence building measure as this makes the breakout time much longer, and this is the stated reason by Iran for the fuel. Stockpiling excess fuel beyond the needs of the TRR is an anti-confidence building measure. Hello to Iran — here’s an idea???

    • mark (History)


      There is no “breakout timeline” in my post. This is solely about the time it would take Iran to reconvert the enriched U3O8 to UF6. I reiterate about why I went to the bother of doing this: Some Iranian web sites and news reports opine that the converted oxide has no proliferation relevance. Some Israelis opine instead that there is no difference in proliferation relevance between the oxide and UF6. In between are the facts.

    • Cthippo (History)

      The problem with irradiating the fuel is that it would turn a relatively safe, inert material into a dangerously radioactive one which would be far more difficult to track and verify. I’m not sure of the numbers, but a short burnup irradiation is also the ideal environment for producing plutonium, which would then introduce a whole new element into the mess (pun intended ex post facto)

    • Anon2 (History)

      Agreed that radiating the TRR fuel makes it hotter.

      But why is that more difficult to track?

      With regard to the extra plutonium, is that not there in the old TRR fuel that they are replacing anyhow. Putting trace amounts of plutonium and other isotopes into what had been relatively pure uranium seems to me to be a good tradeoff. And it still has to be extracted in hot cells does it not?

    • Cthippo (History)

      Uranium, even highly enriched uranium, is a pretty low grade alpha emitter, you can hold it safely in your hands with no problem. Verifying it would be as easy as picking it up and looking at the seals or serial numbers or whatever.

      Once it’s been in a reactor for a while the daughter products from the fission make it a nasty beta and gamma emitter and so it has to be stored under water, which also keeps it cool. The conversation would go something like this…

      (IAEA inspector) I want to see plate number 127791xf

      (Iranian tech) OK, there it is at the bottom of the pool. See it down there?

      (Inspector) How do I know it’s the same plate?

      (tech) Well, you can either trust me that it is, or you can fish it out of there and you can get your annual radiation dose while you read the serial number. Up to you

  6. rwendland (History)

    mark, I still find the way you are expressing the amount of 20% enriched U confusing, if not wrong. The exact wording in the IAEA Feb report on the amount is:

    “280 kg … of UF6 enriched up to 20% U-235, of which 167 kg remain in the form of UF6 enriched up to 20% U-235”

    So 113 kg of 20% enriched UF6 has entered the oxide conversion process. 67.5% of UF6 is U. 67.5% of 113 = 76.275

    That is 76.3 kg of 20%-enriched U entering the oxide conversion process. So don’t you think your wording above for that:

    “By late February, then, Iran had accumulated about 110 kg of 20%-enriched uranium which was not in the form of UF6”

    is, at best, confusing? Why not use 76 kg U amount in that, rather than the UF6 amount?

    • mark (History)


      Your point is well taken, thanks for making it. So to clarify I’ve edited the post accordingly to identify the amounts of uranium present in these materials. If Iran devotes 15 kg of UF6 per month to production of U3O8, adding the uranium value from this to the uranium value in the material processed through February, by the end of the year the total might be roughly 175 kg U in U3O8.

    • rwendland (History)

      Mark, that reads better now. Though your historic quote from the last post “IAEA in February puts the 20% U-235 inventory at 280 kg” still could easily confuse – perhaps you should slip “[UF6]” in there now.

      MH: Done!

      I should have said above, that the article overall is an impressive piece of work, and I’ve certainly learnt from it.

      My only significant concern is Susan Voss’s (former 22 year LANL staffer) point that Iran’s UF6 to U3O8 conversion in 2011/2 was only 39% efficient, with 61% presumably going into other compounds of U. I’ve not confirmed this from the numbers myself, but if true and that level of (in)efficiency has continued into this year, it likely makes make recovery of nearly all of the 20% U back to UF6 rather more difficult for the Iranians. Guessing, maybe a few weeks to recover half, but a bit more time to recover 90% of it.

      MH: The February report says that only 50 kg of the 110 kg UF6 fed into the conversion line was by late February converted to U3O8. I’m informed Yadlin last week suggested in the radio interview that now the amount available in “powder form” [U3O8?] is 80 kg. I will soon obtain a transcript of the radio interview and I will post that information then.

      Two questions thereby arise: 1.) Would Iran not have access to, and not be able to convert back to UF6, the other uranium compounds not originally converted to U3O8 at FPFP? and 2.) Would inefficiency in the conversion factor from UF6 to U3O8 imply that the same inefficiency would obtain for converting oxide to UF6 in the reverse direction?

  7. Rob Goldston (History)

    This is very helpful. It seems obvious that if you can make UF6 from yellowcake, you can make it from 20% enriched U3O8, but it is nice to get a timeline and note the subtleties.. The Iranians would not start their breakout with this material, but they could move to it after a couple of weeks.

    Somehow it seems that this is just the sort of twist that must give them great pleasure.

    The true red line is kicking out inspectors or going beyond 20%. For this, I wouldn’t mind some realtime tamper-evident monitors.

  8. Olli Heinonen (History)

    An important part of the equation are the fuel plates and assemblies produced for the TRR. Why Iran has not produce more them and irradiated them at the TRR? There are good technical reasons not do that at this stage. First of all, the production of fuel assemblies in Iran and elsewhere is much a manual operation. This is first time when Iran produces such fuel assemblies, which require rigorous quality control and testing to ensure the safe operation of the reactor. Therefore, it is important to see , inter alia, the irradiation behaviour of the assemblies before producing a big number of them. In coming months we will likely see a post-irradiation examination of the first element, which was put into the core of TRR a year ago.

    • Cthippo (History)

      I suspect there is also a political factor at play here too. If this was, say, Elbonia or some other random country that no one was worried about they probably would have enriched some uranium, made a few plates, and tried them. For Iran, the establishment of their right to enrich up to 20% is important politically and so they keep doing it not because they need the fuel right now, nor are they able to use it yet, but to establish a norm of doing so. To put it another way, they’re making more than they need or can use right now because continuing to make it is politically valuable. If they said tomorrow “we’ve got enough of this stuff for the next hundred years and we’re going to stop enriching to 20%” it would be characterized as a political defeat or surrender, so the centrifuges keep spinning.

  9. Jay (History)


    Thanks for engaging the facts and thoughtful responses. I certainly learned from and enjoyed the conversation. The contributions from others, for example Olli Heinonen, and rwendland emphasized the intricacies involved in this debate. To make progress all sides need to exercise more care not to lose sight of the context.

    • mark (History)


      That’s the beauty of the blog. We can all learn as we go. I’ve learned a lot from these comments. Yes, context is paramount. And the more you drill into this stuff the more multifaceted it is. You can’t afford to lose sight of the big picture but dimensions can escape you, e.g., in this case questions about the magnitude of Iran’s process losses… that hasn’t been picked up widely.

  10. Olli Heinonen (History)

    Just a remark about the uranium inventories at the Fuel Plate Fabrication Plant (FPFP). The yield (or efficiency) of converting UF6 to U3O8 is likely much higher than the 39 % Rwedland is giving above. The IAEA reports provide the amount of UF6 moved (and “released”, which means the cutting of the IAEA seals from the UF6 cylinders) to FPFP, but it does not give a full breakdown for material in each step of the process. The reports give the amount of U3O8 produced at certain point of time, which is just one part of the material balance equation. There are all the reasons to believe that the Iranian engineers, with two decades of experience on uranium conversion, can achieve a better yield than 39 %. In addition, 20 % enriched uranium is valuable material. Like the other fuel producers, they have a smal process, at least on the drawing table, to recover uranium from the wastes (albeit only a few per cent of material should end up in wastes).

  11. mark (History)

    In the meantime Yadlin yesterday apparently tried to clarify his previous remarks on red lines and Iran’s uranium U3O8 conversion. From what’s in the Jerusalem Post this morning I’m not sure it’s any clearer:

  12. mark (History)

    More from Susan Voss on the numbers cited by Israelis and media reports concerning Iran’s uranium oxide processing:

    Enriched Uranium in Iran – Are they Close to Israel’s Red Line?

    Do you ever read the IAEA safeguards reports and think they are written in gibberish? That is because the nuclear safeguard community has their own language and culture. I reviewed the most recent report IAEA report published in Feb. 2013, and try to make clear where Iran stands on their 20% uranium enrichment and how close Iran is to what Israeli PM Netanyahu referred to as the “red line” for attack.

    Iran has been developing their nuclear program since the early 1960’s when they teamed with the US under the Atoms for Peace Program. In the mid-1980’s, after the fall of the Shah their program took a decided turn to include the development of nuclear technologies with potential military applications – code word for a nuclear weapons program. Iran’s interaction with Pakistan beginning in the late 1980’s provides a fascinating framework for understanding the art of denial in the development and transfer of nuclear technology.

    Why the difficulty in tracking Iran’s uranium? In the process of going from natural uranium to research reactor fuel the material changes physical and chemical form as well as enrichment level.
    • UF6 gas changes from natural uranium to 20% enriched uranium
    • UF6 is converted to an oxide powder, U3O8
    • U3O8 powder is converted into fuel sheets and placed into fuel plates
    • Fuel plates are combined into fuel assemblies

    Accounting for materials as they change form is a challenging job.
    In September 2012 Israel Prime Minster created a red line denoting the maximum amount of enriched uranium that Iran should be allowed to produce before initiating an attack.
    While Netanyahu did not specify the quantity of material the NY Times provides an estimate of the amount of 20% enriched uranium as 240 kgs in storage. This is not the quantity of uranium but rather the quantity of UF6.
    Does that matter? YES – 240 kgs of UF6, uranium hexa-fluoride, has 162 kgs of uranium. Therefore the clear red line can be interpreted as 240 kgs of uranium or 240 kgs of UF6. A difference in uranium quantity of 78 kgs.

    According to the Times of Israel:
    • Pressed specifically in an interview on Israel’s Channel 2, as to whether this meant an attack would have to come before Iran had enriched 240 kg (529 lb) of uranium to 20% purity — enough for one bomb — Netanyahu did not contest the figures.
    Given Netanyahu was trying to create a clear red line for attack he was unclear as to the quantity of material, the form of material, and in specifying – who should attack.
    This is an important point as according to the NY Times article it is a comparison of 20% enriched uranium in storage – NOT THE TOTAL AMOUNT PRODUCED. Why 240 kgs? This is the amount of 20% enriched uranium that if placed within the centrifuges for further enrichment could be used to produce over 25 kgs of 90% enriched uranium defined by the IAEA as a significant quantity – code for enough material to a produce a nuclear explosive device.

    Per Cameco: Enrichment services are sold in separative work units (SWU). A SWU is a unit that expresses the energy required to separate U-235 and U-238.
    As shown in the figure above, the amount of SWU’s to go from 20% enriched to 90% enriched uranium, i.e. code for weapons-grade material is relatively low as compared to the number of SWU’s to go from natural uranium which has approximately 0.78% U-235 to 20% enriched uranium.
    Per WNA: The enrichment graph shows – 1 tonne of natural uranium feed enriched in centrifuges can produce:
    • 120-130 kg of uranium for power reactor fuel, or
    • 26 kg of typical research reactor fuel, or
    • 5.6 kg of weapons-grade material.
    • WNA: The curve flattens out so much because the mass of material being enriched progressively diminishes to these amounts, from the original one tonne, so requires less effort relative to what has already been applied to progress a lot further in percentage enrichment. The relatively small increment of effort needed to achieve the increase from normal levels is the reason why enrichment plants are considered a sensitive technology in relation to preventing weapons proliferation, and are very tightly supervised under international agreements.
    According to the IAEA 20% and below is considered low enriched uranium and 20% and above is high enriched uranium. Iran is producing uranium enriched to 19.75% but is generally rounded up to 20%.
    Twenty percent enrichment was chosen as the cut-off point because it is difficult to produce a nuclear explosive using 20% enriched uranium and below. As a result there iis a significant difference in the level of security and safeguards between facilities with HEU versus LEU which directly impacts costs and ease of handling.
    The questions are – How much 20% enriched uranium has Iran produced? Where is it located and in what form? Are they increasing their production rate?
    First we need to calculate the amount of uranium in UF6 and in U3O8 to provide a clear basis of comparison.
    Per the February 2013 IAEA report Iran has produced the following amounts of uranium –
    • 280 kgs of 20% enriched UF6
    • 1.6 kgs of the above material was down-blended
    • 280 kgs of UF6 =188 kgs of 20% enriched uranium and 92 kgs of fluoride.
    Iran production of 280 kgs of UF6 is 40 kgs over Israel’s red line quantity of 240 kgs uranium. But not all of the UF6 produced is in storage.
    • 111 kgs of UF6 (equal to 75 kgs of uranium) were sent to the Fuel Plate Fabrication Facility (FPFF).
    • to produce 50 kgs of U3O8
    o =43 kgs of 20% enriched uranium in the U3O8 and 8 kgs of oxygen
    • 32 kgs of uranium must have ended up in the waste stream as a result of the conversion from UF6 to U3O8. But it is not specified by the IAEA.
    • 7 fuel assemblies each with 19 fuel plates are at the FPFF for use in the Tehran Research Reactor (TRR)
    • 95 fuel plates were fabricated at the FPFF for use in the TRR.
    • 2 control fuel elements with 14 fuel plates, 1 fuel plate, and 1 fuel assembly with 19 fuel plates are being irradiated in the TRR (please note some of these numbers are estimates as it is difficult to interpret the IAEA report).
    For more information on the design of the fuel plates go to two earlier posts on nuclear diner and an update from November 2012.


    188 kgs of 20% enriched uranium have been produced within 280 kgs of UF6 –
    • (in comparison to the reported quantity of 167 kgs of UF6 in storage – this does not account for the material sent for conversion and fuel fabrication)
    • 21 kgs out of 43 kgs of uranium in the form of U3O8 is in fuel plates at either the FPFF or being irradiated in the TRR
    • 22 kgs of uranium are in oxide form, U3O8, at the FPFF
    • 32 kgs is in the waste stream at the uranium conversion facility at the FPFF
    • 113 kgs of enriched UF6 is in storage at the Pilot Fuel Enrichment Plant (PFEP) and the Fordow Enrichment Plant
    Summing it up by percentage
    • 11% of the 20% enriched uranium is in fuel
    • 60% is in storage
    • 17% is in a waste form at the conversion facility
    • 12% is in oxide form, U3O8, at FPFF
    Interestingly the production of fuel plates has increased significantly. The FPFF went from producing a few plates to producing what appears to be over 200 since November.

    Good news – bad news:
    • If Israel meant 240 kgs of UF6 per the NY Times, converting to uranium this implies the Iranian production of 162 kgs of 20% enriched U has exceeded this proposed limit by 26 kgs.
    • But only 113 kgs of 20% enriched U is in storage in UF6 and 22 kgs of 20% enriched U in U3O8.
    • The significant increase in Iran’s production of fuel plates for the Tehran Research Reactor may be to ensure that the amount of 20% enr. U material does not sit in storage thereby evoking the “red line”.
    • Bad news? The production capability of 20% uranium has increased and the level of technical capability appears to be increasing as well. This implies that if Iran chooses to have a break away capability they will be able to enrich more uranium faster. Albright ISIS report Figures 7 and 9.
    As always a complicated and interesting issue. Iran’s nuclear program may lead to war therefore it is critically important to understand what are the estimates of material and the progress Iran is making on their program.

  13. mark (History)

    This is an unofficial transcript of what Amos Yadlin said last week on Israeli radio further to his remarks before INSS:

    I gave a very serious, very comprehensive lecture, and I explained the problematic nature of the red line. Crossing the red line – and it is important that listeners know this, and if someone didn’t sleep at night, that they calm down – does not mean a bomb. We are talking about an amount of material which the Iranians have, which they could decide to break out with in another year, or in another five years. Therefore my comment was that the red line is not so red, and that in a way it is very problematic too, because it allows the Iranians, under the red line of 20 percent enrichment, to build a nuclear infrastructure in which they enrich to 5 percent only, but a very, very broad infrastructure with a lot of centrifuges, with a lot of materials, and then they will have the possibility of a very short breakout. That was my comment.
    Let’s be precise. I did not say Iran has crossed. I said that the Iranians are being careful not to cross the line formally. With that said, they have done the kind of feint they know how to do. They have on the face of it redirected 110 kg out of the 250 kg which would have constituted a crossing of the line – but they redirected 110 kg in order to come down below the line. What I brought to the public’s attention is that according to the International Atomic Energy Agency in Vienna, 80 out of the 110 kg that they redirected could be reconverted back to the stockpile of 20 percent enriched uranium within a week or two.

    There is no clue from where exactly Yadlin derives the 80 kg number as the amount of 20%-enriched U3O8 which Iran would have at its disposal for reconversion to UF6. The February IAEA report refers to 50 kg of U3O8 which was produced by the conversion process. Yadlin above gives the IAEA as his source for the 80 kg amount.

    The IAEA data was from late February. Perhaps Yadlin assumes that in March and April Iran produced 15 kg UF6 each month and that all of it was fed into the conversion plant (consistent with my above data). If so, Iran would have produced since the end of February 30 kg more U3O8–but only if it is assumed that the conversion factor from UF6 to U3O8 is much higher than 61% and perhaps something more like what Olli Heinonen would be assuming is the case. If so, Yadlin might arrive at a total of 80 kg as of the end of April.

  14. Susan (History)

    The two issues I see in the conversion of the 20% enriched U3O8 back to UF6 to be further enriched are:
    1. the 20% enriched U3O8 has a higher enrichment level and therefore criticality issues will require different handling and processing than the conversion of natural U3O8 to UF6 and
    2. there is no information as to whether or not the processes are developed or in place for the removal of impurities for the material in waste form to allow it to be converted to U3O8 or UF6.

    Therefore while they may have the ability to convert natural U3O8 to UF6 there is insufficient information to say that they can convert their 20% waste material to UF6 or not without more information from the IAEA.

    WNA has an overview of the steps required to convert U3O8 to UF6 at

    The other question would be is how difficult would it be to remove the U3O8 fuel from the fuel plates that have not been irradiated and convert it back to UF6. The U3O8 fuel is pressed between two sheets of aluminum to create the fuel plate. As shown at

    Again it is a question of removing the impurities and issues of criticality due to the higher enrichment.

    Grossly estimating the amount of uranium for reconversion from the February IAEA report:
    32 kgs uranium in waste+21 kgs uranium in U3O8 in fuel plates +22 kgs of uranium in U3O8 at the fuel production facility for fabrication would give 75 kgs. This includes uranium in the relatively small number of fuel plates that are in the TRR being irradiated and therefore is an over-estimate of the amount uranium.

    Mark – Thanks for keeping the dialogue going.

  15. Dan Joyner (History)

    I have certainly enjoyed and benefitted from your writing over the years – and often said so in comments to your posts. I’ve long appreciated your objectivity and care to consider all sides of the issues, as a good journalist. It seems to me, though, that over the past couple of years you’ve taken what might be described as a more hawkish view on Iran and its nuclear program than I perceived in your writing previously. Take this piece, for instance. Now, I know you take pains to say that you aren’t speculating here on whether Iran has or will take the decision to build a nuclear weapon. And of course you don’t explicitly do so. But do you not see that by choosing to research and address this topic in the way that you have, you are implicitly contributing to the hawkish storyline about Iran and its nuclear “ambitions” that is so prevalent in the West and in Israel? This is the same complaint I often have about the work of ISIS. The subjects Albright chooses to write about, and the tone he employs, and the endless speculation about what Iran MIGHT do with its technological know-how, is so clearly gauged to implicitly – and in his case explicitly – feed the narrative that Iran is at some point going to build a nuclear weapon, breakout of the NPT, and threaten Israel, and so we have to stop that from happening. The narrative that the US and Israel have tried so hard to sell to the world. I guess I’m just wishing there was some more journalistic objectivity in the subjects that you choose to write about, and in the implicit messages you are sending, as I perceive there used to be in your work. I’m really not trying to pick a fight here or come off as critical. I have a very high level of respect for you and your contributions to consideration of these issues. I just submit these thoughts for your consideration.

    • George William Herbert (History)

      Dan, the contrary argument that Iran nuclear ambition denialists are trying to obfuscate the real technical situation and argue that Uranium Oxide fuel is not weaponizable is happening as well. I have heard and seen ill-informed assertions that the process is one-way and puts the 19.7% LEU beyond potential future further enrichment and weapons use.

      Pointing out the mechanisms and difficulty – or lack thereof – of reconverting back to UF6 for further enrichment is necessary and appropriate at this juncture.

      Making everyone aware and clear on the technical issues does not change the fundamental strategic question, of whether they intend no weaponization, intend to stand up on the borderline as a potential proliferator but have no intention to cross the line, intend to stand up on the borderline and expect to cross it at an opportune time later, or are weaponizing now with the veneer of NPT compliance used as a shield.

    • yousaf (History)

      GWH — where did you hear it was a one way street?

    • George William Herbert (History)

      Yousaf – outside the circle of proliferation experts / interested parties. Someone who was coming into it from the “US is being Imperialistic!” political bent, with an audience, who had been told or gotten the impression that it was one-way and therefore the materials were beyond further military use.

      They accepted the information and educated themselves.

      That didn’t change the main thrust of their point, which I avoided getting entangled in as it’s a viewpoint / judgement call rather than a physics / chemistry / engineering issue on which an underlying physical truth can be described and universally agreed to.

    • mark (History)


      My perspective on Iran’s nuclear program has evolved over a quarter century of asking Iran questions and interpreting the answers based on whatever available evidence was at hand or obtainable.

      During the recent and comparatively far shorter period of time you have been injecting yourself into debate on this issue, my perspective on Iran has in fact changed very little indeed.

      I looked into the issue of Iran’s uranium conversion chemistry because, since September 2012, when the IAEA informed that Iran was diverting some of its Fordo UF6 output to the production of U3O8, we have been served convenient and unsubstantiated assertions–by observers or actors on both sides of the debate–about whether Iran could or could not reconvert the enriched uranium oxide back to UF6 in short order.

      Iran’s friends and detractors can claim what they will. I have tried to assemble the facts as we can know them. So far, we don’t have all the data, as we have seen from the invaluable discussion in the blog comments concerning the critical matter of Iran’s uranium conversion process losses.

      The question as to whether or not Iran would or would not reconvert the material, or, beyond that, whether Iran would as you say “break out,” is not treated in this post at all. That is intentional.

      I strongly encourage you to re-read if you have not done so already, the conclusion of this post under the rubric “Bottom Line.” There is really no more to add.

      I submit that the fact that since posting this I must constantly reiterate that I am not indulging in any speculation, about whether Iran would or would not do these things, is a consequence of an increasing polarization about this matter during the last year or two.

      But to suggest or insinuate on the basis of the foregoing that I am biased in any way by virtue of having asked these questions in the first place is unwarranted.

      Given the fact that your own views, some of which are highly contentious, to say the least, have benefitted from the tolerance and even good will of others in the nuclear verificaion community (including on this blog site), the notion that I or anyone else should refrain from asking questions about any of Iran’s nuclear activities or capabilities, because doing so would be politically inconvenient, is–diplomatically expressed–very unfortunate.

    • shaheen (History)

      Dan- you’re being guilty of the sin that you (falsely, in my view) accuse Mark of: you are prejudging his intentions. I for one believe that Mark’s analysis and experience is priceless and useful for whoever is interested in a serious and non-partisan (or at least fact-based) analysis of the Iranian nuclear issue.

  16. Cyrus (History)

    A country hell-bent on making nukes would not make it harder for itself to actually make one, would it? The “Iran apologists” are just reading the news:

    “United Nations International Atomic Energy Agency inspectors have verified that Iran converted about 33 percent of its 20 percent-enriched uranium stockpile, according to two senior international officials. Iran used about 49 kilograms (108 pounds) of the 145 kilogram stockpile to make fuel in the form of metal plates for the Tehran Research Reactor, they said on condition of anonymity because of the issue’s sensitivity.

    “There is some good news overlooked,” Robert Kelley, a nuclear engineer and the IAEA’s former top inspector for Iraq, said today in an interview. “This makes the material much less of a danger for further enrichment, and once it has been irradiated it is of even less concern.”

  17. yousaf (History)

    How about we put it this way: everyone should feel better if Iran did do the conversion to alloy.

    They are very very likely having problems with the manufacture of _decent_ enriched fuel plates, and therefore it makes sense for the IAEA to help them do this conversion as Peter Jenkins and I recently suggested. Here is a link to the types of issues:

    Making these plates such that they will survive (enriched not the dummies) is much more difficult than people think, and even Iranian claims are to be taken with a grain of salt. They may well be able to make some such plates but likely not with proper lifetimes (maybe one reason they are stocking “more” UF6 at 20% than they “should”.)

    Robert Kelley’s view above is correct.

    • mark (History)


      In the not very distant future we will learn how Iran’s first homemade TRR fuel element has withstood irradiation in the reactor.

      Last I heard, which was over a year ago, there were difficulties and uncertainties related QA requirements for uranium and aluminium particle distribution encountered during fabrication.

      In any event Iran has been converting enriched UF6 into oxide at a rate which–subject to the uncertainties discussed in my post about Iran’s UF6-U3O8 conversion factor–would far exceed the lifetime of the reactor, given that last week Iran has signaled to the P5+1 it intends to indefinitely continue converting UF6 to U3O8.

      Especially because Iran’s nuclear program does not provide an obvious and clear rationale for indefinite production and stockpiling of enriched UF6, this is the most important issue to be addressed by Iran and the powers.

      There are two avenues that negotiators could explore to mop up Iran’s enriched uranium output–both 20% and 3.5%: production of UO2 fuel for future PWRs and of oxide/silicide fuels for future research reactors. Moving forward on one or both of these could be built into a negotiated package–but only as I explained in a previous post if states and firms in possession of fuel fabrication technology and know-how were willing to take the political and commercial risk, and only if any technicial assistance provided by the IAEA were given on the basis that the IAEA is permitted to verify that Iran’s nuclear program is exclusively dedicated to peaceful-use activities.

      If such a plan were to move forward during negotiations with the P5+1, that would bring us a lot farther down the road than we are at present, I’m sure you would agree.

      The political will needed to bring this off would be considerable. If it isn’t there, Iran would have one ultimate card to play–its “need” to produce HEU for a future naval propulsion reactor development program. Iran has tipped its hand by showing this card a few times during the last two years. This card could be put on the table by Iran at any time before Iran and the powers sign on the dotted line.

    • yousaf (History)

      I largely agree except this clause can be misused for indefinite intrusions: “the IAEA is permitted to verify that Iran’s nuclear program is exclusively dedicated to peaceful-use activities.”

      There is no such standard. Nuclear technology is dual use.

    • mark (History)

      Without IAEA verification as I describe, and yes that implies there will be an Additional Protocol, either 1.) there will be no deal with Iran, or 2.) the deal will not survive implementation because it will not inspire confidence.

      This post is not the time or the place to get into that question. The post is about the process chemistry of uranium conversion. BTW for all to understand: the post is also not about whether or not Iran would or would not convert the oxide back to UF6.

    • yousaf (History)

      The AP goes a long way towards verifying “that Iran’s nuclear program is exclusively dedicated to peaceful-use activities” but not all the way.

      So if you mean AP, I think much better to say AP instead of “verifying that Iran’s nuclear program is exclusively dedicated to peaceful-use activities” which some people may think means more.

      MH: It doesn’t matter whether “some people” think the AP means something else. We know what it means. And it means what I said it did above and which you correctly quote back: “Verifying… peaceful-use activities.”

      The objection you made in your initial intervention, that some activities are dual-use, is a non-sequitur. The fact that specific activities may or may not have a peaceful-use application does not prevent the IAEA from drawing an overall broader conclusion about whether on the basis of its aggregate information a state’s nuclear program is dedicated to peaceful-use activities and that there are no undeclared activities. On an annual basis, the IAEA draws such conclusions in numerous other member states where an AP is in force.

  18. Miles Pomper (History)

    Yousaf and Mark I find much of this discussion besides the point.
    The question is does Iran need to use the TRR to make medical isotopes as it claims.
    The answer is no–it is already importing some of its Mo-99 from Russia and could import more from Russia or from other countries (as it from 2007). And I should hasten to mention that one of the countries Iran could import from is South Africa, that NAM champion, if Iran wants to avoid reliance on the West.
    This is either a vanity project for Iranian scientists with a very poor medical isotope production technology (neutron capture is much less efficient than using LEU targets in a reactor with a processing line like South Africa does, a cover story for Iran to stockpile 20% LEU for a weapons program or both.

    • mark (History)


      The issue you raise doesn’t invalidate an investigative treatment of Iran’s uranium conversion capabilities. It does, of course, go beyond the chemistry and into the question–which I already said I have strenuously avoided in the post–of why Iran is producing the U3O8. Iran has given its reasons. Others may speculate.

    • hass (History)

      Miles may be interested in reading what Geoffrey Forden wrote about this on this very site.

      The fact that even today Iran has been effectively cut off from importing medication under sanctions validates a concern about relying exclusively on foreign sources for anything.

    • anon (History)

      Miles, two comments:

      First, by this logic, no one needs to produce medical radioisotopes as long as they can buy them from someone else. There is the threshold question when it makes sense for a country to produce them for itself. I suspect that Iran (with over 1% of the world’s population) is at least close to that threshold, but it is certainly well below the threshold where it might need more than one research reactor. So Iran can make a credible case that it needs fuel for TRR – but the claim that Iran needs to keep producing near-20% LEU for future research reactors is not credible.

      Second, there are many medical radioisotopes other than Mo-99. As far as I know, Iran has not tried to produce its own Mo-99. In fact, one concern has been that Iran would use Mo-99 production as the justification for producing HEU targets.

    • Rene (History)


      You say: “the claim that Iran needs to keep producing near-20% LEU for future research reactors is not credible.”

      I agree with your statement, but it doesn’t necessarily mean that Iran’s production of 19.75% LEU is aimed at producing HEU. I think at this stage Iran *has to* continue production of 19.75% LEU, because otherwise they wouldn’t have a decent bargaining chip in the negotiations. And I think Mark’s point that the final card Iran may have to play is to move to HEU production for a future naval propulsion system is in the same spirit; if the other side is escalating the sanctions, then Iran would also need to escalate. Well, I hope no one escalates, but both sides appear to be macho!

  19. Miles Pomper (History)

    I agree. I found your posts quite informative and useful.

    But it does raise questions about Yousaf’s proposal for helping Iran try to improve a poor process for medical isotope production as some sort of inducement. We should either dangle real techology (ie an LEU target processing plant) as an incentive or not bother. And I favor not bothering at least until Iran is more forthcoming in negotiations as this is not affecting Iranian public health.

    • yousaf (History)

      I am only interested to try to make safer gaseous UF6 at 20%. If Iran says it wants it for fuel, then let’s help them get it out of the more proliferation risky gas form.

      There are of course many many other proposals that could be suggested, but they don’t seem to be going anywhere, in part because of what hass said: sanctions.

      We can also add other solutions to the one I suggest. But what I suggest is a start.

  20. b (History)

    A big thanks to Mark for discussing the rather complex issue.

    When I pointed out that the IAEA report showed the conversion to U3O8 I assumed that the process of reconversion was more complex than it seems to be. What I it did not assume though is such a relative high loss during the process.

    If these steps are […] an accumulation of higher enriched Uranium on the way to a speed run to a bomb (for which there is no sign) why would Iran take such an unnecessary expensive way to do so?

  21. Bahram Haqtalab (History)

    It seems to me that this article is barking up two wrong trees: (1) the possibility that Israel will attack Iran, and (2) the possibility that Iran will want to make nuclear weapons.

    As for (1), Israel’s talk about a red line must be a bluff. An Israeli attack will cause Iran only a short-term set back, and it will greatly strengthen Iran’s hands in the negotiations. In addition, it might even provide Iran with the political cover needed to pull out of the NPT. Iran would then use rejoining the NPT as a huge bargaining chip in the negotiations, giving it far greater leverage than anything the Unites States can muster short of an actual American attack (which would be equally unlikely under this U.S. president). Iran and Israel know all this, and neither side thinks there’ll be an attack. Israel will attack only if it thinks that would lead to a US-Iran war.

    As for (2), does anybody still seriously believe Iran wants to make nuclear weapons? Have you learned nothing since 2003? Shall we go over the evidence again, beginning with the fact that Iran indicated in 2005 that it would ratify the Additional Protocols if it were allowed to keep enriching up to 5%? Iranian leaders want economic prosperity and normal relations with the rest of the world more than anything else (but not at the cost of accepting neo-colonialist domination), and having nuclear weapons wouldn’t help that cause.

  22. mark (History)

    Fredrik Dahl at Reuters followed up on the blog post:

    Mark Fitzpatrick chimed in on Twitter @FitzpatrickIISS that in his view Iran’s conversion of the UF6 to U3O8 means very little because Iran could reconvert it back to UF6 quickly after learning how to do it.