Much has been said about the decision to refuel Iran’s Tehran Research Reactor (TRR) and many have worried about possible consequences for proliferation that supplying Iran with uranium enriched to 19.75% U235 might imply. As I hope I made clear, I am a big supporter of this deal. However, we definitely want to make sure the details of the deal reassure the West, not increase their suspicions; something that has already occurred with John Bolton. (Ok, perhaps it is impossible to increase Bolton’s suspicions of either Iran or the Obama administration, but you get my point.) Unfortunately, the form of uranium that Iran is currently using, powered U3O8 pressed and perhaps sintered into a box, just about begs to be further enriched: it’s the starting point for the production of UF6. Perhaps it needs to be broken up a bit but, as I showed in my recent post on molybdenum contamination, if the West supplies Iran with fuel in that form, it could be enriched to weapons grade in one step through the centrifuges without worrying about damaging the apparatus.
Three Components to Effective Non-Pro Barriers
While considering steps to increase the proliferation resistance of the TRR fuel, it is important to remember that there are three components to any proliferation barrier and that all three must work together to produce an effective barrier. These components involve technical, legal, and organizational aspects. Without all three components, no barrier is effective. The example I like to give is the humble inspection seal: a piece of tape used to ensure, for instance, that a piece of equipment is not moved or used for illicit purposes between inspections. The seal itself is the technical component and quite a bit of work has gone into its development to ensure it is not surreptitiously replaced or tapered with. However, a seal is meaningless without the legal component that gives some agency (like the IAEA) the right to periodically inspect the seal. And, of course, you need the organizational component so that you have trained inspectors who actually go and inspect the seal. When we think about creating barriers around the TRR refuel load, we do not need to think of a technical barrier that works independently of other barrier components.
Let us start off with the technical component. In designing this portion of the barrier, we cannot impose onerous conditions on the use or form of the fuel. For instance, it must meet all relevant ASTM specifications. Anything else could, and should, be immediately rejected by the Iranians. This severely limits some of the ideas people have posted here. (It rules out “salting” the fuel with a radiation barrier such as U232 since ASTM standard C996 limits the uranium isotopics.) At the same time, if the West imposes conditions like requiring all the LEU feed stock for the TRR fuel to be shipped out at one time, it seems only equitable that the enriched fuel should be shipped back as expeditiously as possible. It is conceivable that the first reactor load fabricated might arrive first to allow the Iranians to install it and convince themselves that what ever form it is in satisfies their needs without redesigning their reactor. But after the Iranians give their go ahead, the future loads should be made and shipped back as fast as possible.
The first technical component should be a new form of the uranium. There are, however, a number of requirements it should meet. First, it should, as much as possible, have the same neutronics (i.e. the same density of uranium in the fuel rods) as the old fuel. It turns out that quite a bit of thought went into designing new types reactor fuel rods during the 1990s when there was a push on to switch from research reactors using essentially weapons grade uranium to “low enriched uranium.” Low enrichment is rather arbitrarily defined as less than 20 percent, presumably because the resulting critical mass is over 400 kg; an amount that just doesn’t seem weaponizable to most people.
Beryllium to the Rescue
Based solely on reactor uranium loading, the best match for Iran’s TRR fuel rod density (of 2.96 grams of uranium per cubic centimeter, gU/cm^3, according to the Iranian publications) is alloying uranium and beryllium in the form of UBe13 (i.e. thirteen atoms of beryllium for each atom of uranium). Perhaps not surprisingly, the resulting density of the alloy is very similar to the uranium oxide powder Iran current uses (4.37 g/cm^3 as opposed to the current 4.76 g/cm^3: not even the mechanical support structure of the rods will need to be changed. Replacing the oxide with a beryllium compound immediately increases the time it would take Iran, if it chose, to convert it to UF6 for further enrichment.
It is very doubtful that Iran already has much experience with industrial scale beryllium processing. And while it is conceivable that Iran could acquire lab-scale expertise at separating uranium from beryllium using natural uranium in its tests, it would be a major technological challenge to take experience and turn it into a process for efficiently separating 150 or so kilograms of uranium. After all, the Russian nuclear industry doubted its ability to reprocess uranium-beryllium alloyed spent fuel rods as late as 2006.
If UBe13 alloy fuel rods represent a very significant time and technology barrier to further enrichment, they do not represent an absolute barrier. That is where the other components to proliferation resistance come in. Clearly, an increased time barrier is most effective when it is accompanied by either periodic or continuous monitoring of the fuel supply; something that was already in place for existing fresh fuel stocks. For most of the time Iran had fresh, 19.75% enriched U3O8 fuel rods sitting around waiting to be used (since 1992) it did not have a significant enrichment capacity. Now that it has, it is only natural that the periodicity of the monitoring be increased.
The best situation would be if the fuel supply was remotely monitored by video cameras. However, the procedures for such continuous monitoring have not been worked out with Iran, even for Natanz, so we should at least insist on video monitoring of the fuel with periodic film pickup—typically once every two weeks. This together with the safeguards already in place at Iran’s other nuclear facilities—at the enrichment halls at Natanz and the conversion facility at Esfahan—should provide the organizational components.
Finally, Iran needs to agree to the monitoring of this fuel regardless of its future NPT status, i.e. placing the fuel under safeguards in perpetuity. This legal component is obviously necessary and fair. The P5+1 is agreeing to provide a service, the further enrichment of uranium, that will in all practical circumstances be irreversible with the understanding that it will never be used for weapons purposes; something Iran says it agrees with.