by Ivanka Barzashka and Ivan Oelrich
A year ago, France, Russia and the U.S.—called the Vienna Group—proposed a deal in which Iran would ship out some of its worrying low-enriched uranium (LEU) in exchange for fuel for its medical isotope reactor, called the Tehran Research Reactor (TRR). These narrow technical discussions about the TRR were meant to serve as a confidence-building effort. The negotiations fell apart because of differences about timing of the exchange of material, but they may be about to restart. A year later, the facts on the ground have changed. These new circumstances may call for new negotiating terms, but changes have to make some sense. Calculations show that numbers recently floated by the State Department seem ad hoc and arbitrary and will not have the touted threat-reduction benefits.
On October 27, The New York Times reported that a senior U.S. official believed that the Vienna Group were “very close to having an agreement” on how the original fuel swap offer, made in October 2009, should be changed. One of the new terms would be an increase in the amount of LEU provided from 1,200 kg to 2,000 kg. The State Department explained a day later that “the proposal would have to be updated reflecting ongoing enrichment activity by Iran over the ensuing year.” Iran’s larger LEU stockpile changes Washington’s threat-reduction calculus, which ultimately undermines the confidence-building aspect of the deal.
Another new circumstance is Iran’s production of 20 percent enriched uranium, ostensibly to produce TRR fuel domestically. This is a worrying development because, compared to LEU, a stockpile of 20 percent material would cut by half Iran’s time to a bomb.
Understanding the threat-reduction calculus
Any threat-reduction benefits of the deal were a function of the fuel requirements of the TRR. The TRR needs about 120 kg U of 20-percent enriched uranium to fully fuel it, which would allow it to run for about another 20 years. This is what Argentina sold to Iran in 1992 when the reactor was last refueled. To produce the fuel requires as input 1,200 kg of uranium hexafluoride (UF6) at a 3.5 percent concentration. (In all cases below, quantities are in UF6 unless otherwise specified; UF6 is about two thirds uranium by weight.)
The October 2009 fuel deal contained two threat-reduction components. First, the 1,200 kg of LEU needed for the reactor is, purely coincidentally, the amount that, if further enriched, could produce enough highly-enrich uranium (HEU) for one crude nuclear bomb. Shipping out the material, therefore, reduces by one the number of bombs Iran could potentially make at any given point in the future. Second, Iran would have been left with 450 kg of LEU if it had shipped out the 1,200 kg in October 2009—which is too little for feedstock to produce enough highly-enriched uranium for a bomb. For the short term, this would have prolonged Tehran’s time to its first bomb. To get the LEU out of the country immediately, the Vienna Group insisted that Iran escrow its material in Turkey. Tehran originally refused, but yielded in May as a last-minute attempt to derail UN sanctions.
In theory, leaving Iran with less than a bomb’s worth of LEU provides strategic advantage. If Tehran were to rush towards a bomb, adding time to the clock is important. But this was always going to be true only during a fleeting period. Stopping enrichment was never an explicit part of the deal. With Iran continuing enrichment of uranium, it would have replenished its stockpile by now even if the swap had gone through last year. The threat-reduction advantage of the deal made a great selling point but, without suspension of enrichment, never provided any long-term strategic advantage. It was a gesture meant to build confidence in the West that Iran was ready to engage.
Today, Iran has a stockpile of about 3,100 kg LEU (2,803 kg as of Aug 7 IAEA data plus an estimated amount based on average production rates) or an additional 1,450 kg since Oct 2009, when the deal was first proposed. If Iran shipped out the original amount of 1,200 kg today, it would be left with 1,900 kg of LEU – or enough to be further enriched to a bomb. In an attempt to salvage the threat-reduction advantage, Washington has, according to the NYT, decided to increase the swap amount to 2,000 kg.
Iran has also produced about 30 kg UF6 of 20-percent enriched uranium. The NYT writes that under the new proposal, Iran would be required to “halt all production of nuclear fuel that it is currently enriching to 20 percent.” Although the article does not mention that Iran would have to also export all of its 20-percent uranium, this will likely be a key part of any new fuel arrangement.
More LEU shipped, more fuel sold
If Iran exchanges more LEU, it would receive more nuclear fuel in return. The 2,000 kg can produce 200 kg U of 20-percent research reactor fuel. Iran’s accumulated 30 kg, enriched to 20-percent correspond to 20 kg U of fuel. Under these new conditions, Iran would be buying almost twice what it requested — about 220 kg of fuel or enough to power its medical isotope reactor until 2050 when it will be 83 years old. It is very unlikely that Tehran will agree to this option.
The Vienna Group might offer to use the additional LEU as partial payment for Bushehr fuel. This means that 1,000 kg at 3.5 percent and 30 kg UF6 at 20 percent will be exchanged for 20-years-worth of TRR fuel, and the other 1,000 kg will offset several percent of Bushehr’s annual fuel consumption.
One advantage of a reactor like the TRR is that a fuel load can last two decades. Refueling the reactor could be a one-time symbolic confidence-building measure that, even it sets a precedent, does not set a precedent that has to be dealt with for another two decades. Using Iranian enriched uranium for the Bushehr reactor runs a greater risk of legitimizing the Iranian enrichment program into the indeterminate future.
More LEU, more time to a bomb?
Washington’s reason for increasing the swap amount is to leave Iran with less than a weapon’s worth of LEU. But if Iran ships out 2,000 kg UF6 today, it will be left with 1,100 kg UF6, which, if further enriched, could produce enough material for a nuclear bomb. The new condition will not achieve the goals the U.S. claims to be aiming for.
What are some possible explanations for this error? Option 1: Perhaps the State Department used old data or these “new” terms were supposed to be put on the table months ago. According to the most recent IAEA report, Iran had produced 2,803 kg on Aug 7. If the State Department used these latest statistics, without approximating the additional LEU produced over the last 3 months, it could be misled into thinking that swapping 2,000 kg would leave Iran with 800 kg UF6 – or below the bomb threshold.
Option 2: Perhaps the State Department is talking about 2,000 kg of uranium metal, not UF6 even though all IAEA and past discussions have used UF6 weights. Presumably both the 2,000 kg and the 1,200 kg are in the same mass units, either uranium metal or UF6. (Two out of the three State Department and IAEA officials we asked said that the original swap amount was in UF6, not U.) Requiring Iran to exchange 1,200 kg of UF6, not U, makes more sense for a couple of reasons. We know that the amount swapped corresponds to 120 kg U in fuel (since the fuel is an aluminum-uranium alloy, this is in uranium mass). Iran enriches UF6 at Natanz and the IAEA measures all output in UF6 mass. If the 1,200 kg are U, this implies a waste concentration of 1.7%, which means that significant U-235 would be wasted by further Russian enrichment, which is unlikely. Iran itself could already be more efficient in producing 20% uranium: the two-cascade system at the pilot plant has a waste concentration of 0.7%.
This is only an example that getting Iran below the “bomb threshold” has always a moving target.
A fuel deal is a necessary, though not sufficient requirement for further diplomatic engagement with Iran. Changed circumstances, like Iran’s 20-percent enrichment, indeed require for the original terms of the swap proposal to be altered. But there are several issues with Washington’s alleged new proposal.
First, the 2,000 kg will not leave Iran with less than a weapon’s worth of uranium. Second, any increase in the swap amount would be counterproductive. It offers little strategic advantage, but provides Tehran with an excuse to keep stalling. Third, it is difficult to technically ground the hike in LEU to be swapped. The most plausible justification – to use the extra uranium as partial payment for Bushehr fuel — risks legitimizing Iran’s uranium enrichment.
Delays have a price. Iran will keep producing LEU and 20% uranium. Any strategic benefit is reduced every day that a deal is not signed. If Iran agreed to the condition to ship out more uranium, but did so 6 months from now, Washington would have to renegotiate the swap amount again. In the mean time, Tehran’s stockpile of 20% uranium will cut by half its time to a bomb and Iran would have advanced towards own fuel production. (Iran informed the IAEA that it will begin installing equipment at the Uranium Conversion Facility and Fuel Manufacturing Plant this November.) Once Tehran makes its first fuel element, it will no longer have the need for a fuel deal and higher-level enrichment could become a permanent development. Delays in selling Iran reactor fuel — what is normally a straight-forward commercial transaction — also strengthen the mullahs’ claims that there are no credible nuclear fuel guarantees and, therefore, their justification for domestic enrichment.
To empower new voices to start their career in nuclear weapons studies, the Federation of American Scientists launched the New Voices on Nuclear Weapons Fellowship. Here’s what our inaugural cohort accomplished.
The FAS Nuclear Notebook is one of the most widely sourced reference materials worldwide for reliable information about the status of nuclear weapons and has been published in the Bulletin of the Atomic Scientists since 1987. The Nuclear Notebook is researched and written by the staff of the Federation of American Scientists’ Nuclear Information Project: Director Hans […]
[UPDATED] The Biden administration has decided to add a new nuclear gravity bomb to the US arsenal. The bomb will be known as the B61-13.
New satellite imagery shows that preparations to deploy Russia’s new Sarmat intercontinental ballistic missile are well underway.