Source: Arms Control Wonk

In January I discussed the prospects for including a serious nuclear cooperation component in a future comprehensive deal to resolve the Iran crisis, permitting Russia to provide Iran with PWR fuel-fabrication infrastructure to complete the front end of its civil nuclear fuel cycle and at the same time incentivize Moscow to firmly line up with the EU-3/US group. At the end of the day, it was evident that going this route would require a lot of Russian heavy lifting and more than a modicum of Iranian trust.

But if such a scheme is ambitious, then the gambit put forth this week by Peter Jenkins and Yousaf Butt must be categorized as minimalist. Their proposal was hatched on a Reuters blog on Thursday.

The bottom line would be that if the P5+1 aims to reduce Iran’s stockpile of UF6 enriched to 20% U-235, now being churned out at Iran’s underground Fordow site, then the powers should offer Iran to help it convert this inventory into uranium metal and process it into fuel plates for the TRR reactor. The driver behind this idea is that the IAEA has documented that Iran has continued to produce more and more 20% EUP, but also that it has dedicated a large share of that output to the production of U3O8, which is what Iran right now has to work with if it want to produce TRR fuel.

The key passage seems to be this:

But Iran appears to be having some technical problems in doing the conversion – especially in fabricating the enriched uranium fuel plates. So the world powers could encourage the IAEA to assist Iran in this conversion and subsequent fuel plate fabrication. Iran would get fuel for its reactor and, in the process, turn potential bomb fuel into a safer form.

We’ve been all over the TRR before, for five years, in fact. Are the facts on the ground right now any different than they were in 2009? Does a “TRR deal” today make any sense?

Apart from the fussy nit that what is happening in Iran is the re-conversion of the UF6 to oxide, followed by a separate process of using U3O8 product to manufacture fuel the TRR reactor, and what looks like a misunderstanding or oversight concerning the potential value of converting UF6 to uranium metal, the critical facts would appear to be these:

Iran’s Inventory of 20% U-235

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 puts the 20% U-235 inventory at 280 kg, of which 167  kg was 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. Based on Iran’s ongoing installation of centrifuges, in theory Iran could produce as much as three times that amount, as spelled out in this ISIS report.

Iran’s Requirements for the TRR

On the basis of the performance history of most material test reactors, my notes distill that at a rating of 5 MW, if the reactor were to operate for half a calendar year, the TRR would use just under 13 kg of fuel per year enriched to 19.75% U-235., assuming an average discharge burnup of the fuel of 45%. That kind of duty cycle length and fuel burnup is de rigueur for material test reactors like the TRR. The exact amount of fuel needed for a year would depend on the exact operating schedule of the reactor, fabrication losses, and the real power level (not the nominal rated level) of the reactor. If we assume fabrication losses of about 15%, Iran might need 15 kg/year to make enough fuel to operate TRR like most MTRs are operated.

This morning I found a previous post by Geoff Forden back in 2009, which suggests that my generic MTR data track well with an unreferenced IAEA report showing that average burnup of the TRR fuel has been 42%, and that the reactor has been operated on-off on a weekly basis.

The record would also suggest that the TRR in the past was operated like other MTRs worldwide. But Iran since 2009 has claimed that it wants to operate the TRR to make medical isotopes. If we assume that, then Iran would want to operate the TRR on a near-continuous basis. Operating at 80% of the time, the fuel fabrication requirement would be about 24 kg/year enriched to 20% U-235 if all the other variables were the same.

What to Conclude from the Numbers

The current inventory of 280 kg of 20% EUP which Iran has accumulated since it began enriching at this level just three years ago is enough to meet Iran’s requirements for more than twenty years if the reactor were to continue to operate as in the past, enough for a decade if Iran were to be successful in operating the 1960s-vintage machine flat out to produce isotopes round-the-clock. Beyond this, if Iran were to continue to produce 20% enriched EUP at current rates, it will produce annually seven times the amount of EUP Iran would need for TRR if it were to be operated at a high duty cycle for isotope production. If Iran increases output of 20% enriched uranium based on its deployed capabilities, it might make enough TRR fuel feedstock in a single year to operate the reactor for two to four decades.

So a gambit to build down Iran’s higher-enriched uranium inventory might fit into the picture as a CBM for the diplomats. But at Iran’s current rate of production of 20% enriched EUP, it is already piling up an inventory of higher-enriched feedstock which in relative terms would resemble the kind of surpluses which Russia has accumulated at its civilian reprocessing plant at Ozersk because Russian reactors can’t burn the plutonium fast enough.

The Butt/Jenkins piece proposes that the P5+1 help Iran process the UF6 into metal fuel instead of U3O8. They argue that the metal form would be “safer” and “more proliferation resistant” than UF6.  It would be more chemically stable and hence safer. But uranium metal can be fairly quickly converted back to UF6.  There might be a virtue in converting the UF6 to metal that the authors didn’t mention: Metallic uranium would be an intermediate stage in the production of uranium silicide that is used in fuel worldwide for MTRs like the TRR which since the 1980s were converted from HEU to LEU fuel.

Right now Iran has neither the technology nor the expertise to produce fuels on the basis of U3Si2 in powder form. There are a number of fabricators that do have this knowhow–in Argentina, Chile, China, France, Indonesia, and South Korea–and perhaps one of these, as part of a P5+1 deal with Iran, could step in and provide assistance.  On the basis of experienced accumulated by the U.S. DOE RERTR program worldwide, it would not likely be difficult for Iran to replace U3O8 with U3O2 fuel in the core of the TRR.

But if the powers negotiating with Iran were to contemplate a new TRR fuel deal with Iran and it failed to materialize, the most likely showstopper might not be whether Iran could be provided access to fuel production technology but the fact that Iran already has lots of feedstock to make the fuel on the basis of U3O8, the IAEA’s inventory data which suggest that Iran made enough fuel feedstock to operate the TRR for perhaps 3-4 years, and the expectation that Iranian scientists and technicians will on their own solve their fuel re-conversion and fabrication problems.

Back in 2009, even before Iran began enriching uranium to 20% U-235, Tehran warned that it would do that to produce medical isotopes in the TRR unless the P5+1 powers accomodated Iran and struck a deal. That didn’t happen, and now, four years later, Iran still has its TRR, and it has enough enriched uranium fuel to operate the reactor for many years. The P5+1 could repeat its offer to fabricate TRR fuel (in this case, help Iran fabricate it, as Butt and Jenkins plead), but given the fact that Iran has carried out its 2009 vows and is now making the fuel, the powers have little to offer here that would interest Iran. Iran will probably figure out how to get the temperatures and pressures right to reconvert the UF6 to U3O8 at the FPFP re-conversion plant at Esfahan, just as it figured out over the last several years how to operate the UCF plant in the same location.

A lot more than this will have to be put on the table by both sides before diplomacy shows real results.

This article was originally published in Arms Control Wonk.