Iran’s 20% Enriched Uranium Stockpile

Iranian President Ahmadinejad looking at a fuel rod at Iran’s research reactor (Image source: The Guardian).

By Greg Thielmann

One of the most significant and underreported developments in the August 30 report of the International Atomic Energy Agency (IAEA) on Iran’s nuclear program was the decrease in Iran’s stockpile of 20 percent-enriched uranium. The sparse attention given to the stockpile figures in the mainstream media was surprising given that the six powers negotiating with Iran have assigned such a high priority to halting and reversing the growth in this stockpile.

In fact, the three P5+1 “demands” emerging from this year’s negotiating sessions all centered around this issue:

  • Stop the production of 20 percent enriched uranium;
  • Shut down the mountain-based facility at Fordow [which is now enriching exclusively to 20 percent];
  • Ship the 20 percent enriched uranium stockpile out of the country.

The logic of pursuing a negotiating strategy that first and urgently addresses the 20 percent stockpile is impeccable. At this concentration of the fissile U-235 isotope, the uranium hexafluoride has already travelled 90 percent of the distance required to reach weapons grade. By the time Iran acquires approximately 225 kg of uranium gas (UF6) enriched to this level, it would be within one month of being able to further enrich to the 90 percent level required for producing the metallic core of a nuclear warhead (assuming it takes 25kg of material for one bomb.)

If on the other hand, Iran only had its much larger stockpile of 3.5 percent UF6 to draw on for producing the weapons grade uranium needed for a bomb, it would take half a year. Large stockpiles of 20 percent enriched uranium thus pose a much more rapid “breakout” option for Iran to build nuclear weapons than it would derive from large stockpiles of 3.5 percent enriched uranium.

The IAEA confirmed in January that Iran had begun producing 20 percent enriched uranium at the deep underground (and less vulnerable) facility at Fordow. Former IAEA Safeguards Department chief Olli Heinonen noted then that: “At current production rates, Iran can expect to have a stock of 20 percent enriched uranium of around 250 kg by the end of 2012…”

Yet, the IAEA’s latest report counted only 91.4 kg in the UF6 stockpile at this level, lower than the 101 kg reported by the agency in May. This decrease is explained by Iran’s continuing withdrawal of 20 percent enriched UF6 for conversion into U3O8 in the form of metallic fuel plates for use in the ageing Tehran Research Reactor (TRR), which makes medical isotopes.

In spite of the growth in the gross amount of 20% enriched uranium produced during the latest quarter, Iran was no closer to being able to achieve sufficient weapons grade uranium for a bomb. Importantly, uranium in the form of fuel plates cannot easily be converted back into the gaseous form required for further enrichment. Even though still enriched to 20 percent, it is essentially no longer available for diversion into a military program.

An equally important detail from the IAEA report is the absence of evident progress by Iran on expanding the number of its advanced centrifuges in operation. More advanced centrifuges could enrich much more efficiently than the older IR-1 model now installed at both the underground fuel enrichment facilities at Fordow and Natanz. The more advanced IR-2 and IR-4 centrifuges are still limited to the three cascades that have been in operation for some time at the above-ground Pilot Fuel Enrichment Plant at Natanz.

Iran does not appear ready to move quickly to put a useable nuclear arsenal in place. Realistic scenarios for Iran breaking out of the nuclear Non-Proliferation Treaty feature both a sizeable stock of 20 percent enriched uranium and deployment of upgraded centrifuges. Commentators like Mark Fitzpatrick (IISS) and  Gareth Porter (IPS)  gave prominent billing to these elements of the IAEA report early on; Walter Pincus later highlighted the 20 percent stockpile in an analysis on the inside pages of The Washington Post. However, most media coverage did not, emphasizing instead the 20 percent enriched uranium production increases and the doubling of centrifuge numbers at the Fordow facility. Whether one focuses on the glass half-full or half-empty, it is clear from the latest IAEA statistics that an Iranian nuclear threat is not yet imminent.

The incremental increases in Iranian nuclear capabilities and continuing resistance to compromise by negotiators on both sides certainly provide ample grounds for concern. But the absence of bad news on 20 percent stockpiles and advanced centrifuges provide reminders that the window of opportunity for peaceful resolution of the Iran nuclear imbroglio is still open. The year following the U.S. presidential election will be a critical period for using diplomacy to bridge the divide. It is not too soon to start exploring creative options.

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23 Responses to Iran’s 20% Enriched Uranium Stockpile

  1. What ” continued resistance to compromise”? Iran has repeatedly offered to cease 20% enrichment in exchange for being able to buy the fuel for the TRR. In fact Iran would not have had to start 20% enrichment if it was not prevented from doing so by the US sanctions in the first place as Iran’s former nuclear negotiator Mousavian points out here:

    Since the TRR poses no weapons threat, preventing Iran from buying the fuel served absolutely no “non-proliferation” purpose, and killing off the Brazil/Turkey deal after Iran said yes prevented Iran from shipping out half of their stockpile.

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  4. HLC says:

    Uranium in the form of U3O8 can actually be converted relatively quickly back into UF6, as U3O8 is one of the basic feeds of the UF6 production process. Although a small portion will naturally be lost in this process, what remains could still be easily used within a breakout scenario.

    However, any converted U3O8 formed into fuel plates for the TRR and subsequently irradiated cannot be simply reconverted into UF6 and easily enriched up to weapons-grade. Unfortunately, this portion of converted (and irradiated) U3O8 is small compared to that which is still available for breakout. The option for peaceful negotiation is indeed still open, and should be pursued above all else, but there is still bad news regarding their growing stocks of 20% enriched uranium.

    • GB says:

      HLC, can you please point me to where in the IAEA report is discussed the percentage of U3O8 and that formed into fuel plates for the TRR?

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  6. GB says:

    What is the evidence of this conversion:

    “This decrease is explained by Iran’s continuing withdrawal of 20 percent enriched UF6 for conversion into U3O8 in the form of metallic fuel plates for use in the ageing Tehran Research Reactor (TRR), which makes medical isotopes.”

    • GB says:

      Also, can you please address HLC’s comment, and paste the statements in the whatever IAEA reports etc from which the percentage of U3O8 and fuel plates for TRR is mentioned? Or what evidence is there of such conversions?

      • Yousaf says:

        see GOV2012/23 para 38:

        “Fuel Plate Fabrication Plant: In a letter dated 2 May 2012, Iran informed the Agency that it had
        decided to combine into one facility the activities involving the conversion of UF6 enriched up to 20% U-235
        into U3O8 and the manufacture of fuel assemblies made of fuel plates containing U3O8, which at that time
        were being performed at UCF and FMP, respectively. In the same letter, Iran also provided the initial DIQ
        for this facility, which it refers to as the Fuel Plate Fabrication Plant (FPFP). A safeguards approach for
        FPFP was subsequently agreed between the Agency and Iran and is now being implemented. Between the
        start of conversion activities on 17 December 2011 and 15 May 2012, Iran has fed into the process 43 kg of
        UF6 enriched up to 20% U-235 and produced 14 kg of uranium enriched up to 20% U-235 in the form of
        U3O8. On 15 May 2012, the Agency carried out a DIV and an inspection at FPFP and verified two fuel plates
        and one standard fuel assembly containing 19 plates, all of which were subsequently transferred to TRR. On
        20 May 2012, the Agency verified a second standard fuel assembly containing 19 plates prior to its transfer
        to TRR.”

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  11. David says:

    It is Possible Iran acquired some U3O8 from some other source and is saying it converted some of it’s 20% Stock to U3O8 when in fact it obtained some U3O8 from another source and is Concealing the amount it said it converted for making of a bomb in secrecy ? Has or Can the IAEA test the U3O8 to see if it really came from the Iranians 20% Inventory? I would not put it past Them to attempt something like this!

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