We have reached a crucial juncture in the progress of the Iranian nuclear-weapons program – and the nature and significance of that juncture are being overlooked in favor of focusing on the reported effects of the Stuxnet worm and international sanctions.

The juncture in question is defined by two factors: Iran’s mastery of the uranium-enrichment process, and her successful testing of missiles that could deliver a nuclear warhead.  Iran has produced enough low-enriched uranium (LEU) for 3-4 nuclear warheads.  The LEU requires enrichment to a higher level of purity to be used in a warhead, and Iran has already started on that process.  Enriching uranium to “medium” purity – 19.75% purity – is being done, in defiance of UN resolutions, at a separate facility co-located with the main enrichment installation at Natanz. Enrichment to a purity level of over 90% (usually given in public literature as 93.5%) is required for use in a warhead, but once the enrichment process is mastered, the leap to high-enrichment is a relatively minor step.

In the realm of delivery platforms, Iran has a missile (the Shahab-3) that can carry a nuclear warhead as far as Israel, the Caucasus, and Central Asia.  The Iranians have also made significant progress with the Sejjil missile program, which is projected to enable nuclear warhead delivery into central Europe as early as 2015.

What Iran lacks is the third factor in creating a nuclear weapon: a working warhead.  Developing the warhead requires enriched uranium to experiment with; a planned delivery platform to impose constraints on the warhead’s weight and design; and the warhead design itself.  Key to the warhead design is choosing and perfecting a detonation apparatus.  Intelligence from the last decade has suggested that Iran obtained information on a certain kind of initiator (uranium deuteride) from the A.Q. Khan network, and has had a program of work on high-explosive tests to pursue successful detonation of a nuclear device.  But the weaponization effort is, overall, the one we know the least about.

It cannot be overstressed that Iran is close to having the high-enriched uranium necessary for warhead experimentation.  This topic is also the right point at which to observe that the Stuxnet worm’s impact on uranium enrichment has been limited.  I am second to none in my admiration of the worm’s crafty design.  But it was deployed to attack the rote mechanics of a process Iran has already mastered, and ultimately, that’s what matters.  Iran has enriched uranium successfully using centrifuge cascades; Stuxnet cannot stop the Iranians from resuming that work.

Moreover, it hasn’t shut down all enrichment, nor has it even penetrated all the enrichment facilities.  This assessment from the Institute for Science and International Security (ISIS) clarifies that while Stuxnet apparently shut down an array in the main facility at Natanz, enrichment continued with the other equipment there through the cut-off date for the latest update (November 2010) from the IAEA inspectors. Not only did it continue, but the enrichment performed by the online arrays was becoming more efficient by the month.  The amount of LEU produced was increasing on a monthly basis, even as some components in the facility were experiencing degradation that was probably due to Stuxnet.  And rather than let Stuxnet-contaminated operation continue, the Iranians, once they were aware of the worm, suspended enrichment at the main facility.  The public has been given no reason to suppose they have lost all their centrifuge cascades to sabotage.

Meanwhile, there are no reports that centrifuge controllers in the separate facility at Natanz where higher enrichment is done – the Pilot Fuel Enrichment Plant, or PFEP – have been penetrated by Stuxnet. Of additional significance, ISIS noted in August 2010 that the Iranians were using a procedure at the PFEP that enhances the use of the LEU it is fed from the main facility.  While ISIS is careful to clarify that this doesn’t mean more medium-enriched uranium is produced, it does mean the LEU feedstock is more fully utilized: more of its remainder is suitable for recycling in the main facility after the medium-enrichment process.  This makes the overall enrichment cycle more efficient for a given amount of uranium.

The point of mentioning this here is that performing this feat adds complexity to the process in the PFEP.  As with the increasing efficiency of the LEU production at the main facility, the Iranians are performing relatively sophisticated operations and achieving success.  There is a growing body of expertise they have acquired, which cannot be somehow taken away from them by breaking some of their equipment, any more than sabotaging the US auto industry’s manufacturing plants would degauss its corporate engineering memory.

The bottom line on the Stuxnet worm is that it attacked a process already effectively mastered.  This is not an impact to be dismissed; recovering from it will almost certainly slow down Iran’s progress toward an arsenal.  But it will not slow down Iran’s progress toward a weapon.

The apparent assassination of nuclear scientists may do that, to some extent.  The extent of the impact – from the loss of particular scientists – will depend on how many others in Iran already had much of the dead scientists’ expertise.  It may also depend on how much fresh outside assistance Iran can get, from Russia, China, Pakistan, or North Korea.

But any impact on the weaponization effort is likely to depend much more on Iran’s ability to obtain scarce materials and precision-machined components – or to perfect her own, indigenous precision-machining capabilities.  If international sanctions truly deny Iran the tools she needs to move a warhead from the design to the testing phase, that will matter to the political situation of the Middle East – at least for the short term.

Americans need to understand this:  it’s the weaponization process we can still get a high payoff from interdicting.  The UN inspection regime and the Stuxnet worm were designed to focus on uranium enrichment.  But uranium enrichment, as a process, is receding in the rearview mirror as a high-payoff target for interdiction by sanctions or sabotage.  It’s not the most important thing to interdict, nor has it been for about two years now.

Yet the UN inspectors have been admitted regularly only to the sites at which uranium is converted or enriched, and their accounting focus is on how much enriched uranium there is.  Stuxnet, for its part, was designed to attack the enrichment process.  (I’ve written on these topics previously here and here.)  Sanctions have been enforced on the basis of companies and international contacts known to have had a role in enabling the enrichment process.  More than 95% of media reports about Iran’s nuclear activities deal with uranium enrichment.  It’s the focus of almost everything we do and say, but it’s not the step at which we can effectively prevent Iran from getting the bomb.  That step, today, is weaponization.

But we have considerably less information on Iran’s weaponization effort.  Even assembling a list of the facilities in Iran where weaponization activities are in progress involves a greater level of uncertainty than making such a list for uranium enrichment or missile development.  It may be that the drastic, distasteful step of assassinating scientists was taken because, for this aspect of nuclear weapons development, Western intelligence agencies’ knowledge about facilities and complicit companies is inadequate to less lethal forms of targeting.

Complacency about Iran’s nuclear program is the very last thing called for in 2011, in spite of what Stuxnet and the most recent sanctions may have achieved.  All of Iran’s important progress has been achieved since UN sanctions were first imposed in 2006, and some key milestones have been achieved since Stuxnet was introduced in Iranian computers.  One of the most important developments is that Iran can now mill and refine her own uranium – meaning that the UN’s basis for accounting on Iran’s stockpile, which has been predicated on yellowcake left over from the 1980s, will soon be irrelevant.  And when it comes to the weaponization effort, we don’t know so much about it that we can say with certainty what the highest-payoff method of interfering in it is.

That’s why Benjamin Netanyahu refuted the policy implication of his outgoing intelligence chief’s statement last week, on the delay of Iran’s progress toward a bomb.  Fox News reported on this, but it hasn’t been given play by other US media, which have preferred to run with the “Stuxnet bought us time” theme.  But while it is very likely to have slowed some aspects of the Iranian nuclear program, Stuxnet’s assessed effects to date will have no impact on the most important aspect politically: Iran’s timeline to a bomb.

It’s conceivable that there will be future news indicating that Iran’s ability to enrich uranium has been shut down entirely.  That catastrophic a development would decisively delay Iran’s progress toward having the fissile material for a prototype weapon – i.e., making the jump from 19.75% to 90%+.  We can certainly be on the watch for such a report.  In the meantime, the focus on Stuxnet is emblematic of the popular, outdated focus on interdicting enrichment, when what needs to be interdicted is weaponization.

J.E. Dyer blogs at The Green Room, Commentary’s “contentions” and as The Optimistic Conservative.  She writes a weekly column for Patheos.

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