Why Iran sanctions must stay

The sanctions adopted by the European Union and most developed countries may yet induce Iran to sincerely enter into negotiations on how to keep its nuclear programme from being used for weapons purposes. But whether or not such talks ensue and are productive, the strict implementation of sanctions can accomplish something else very important: limiting Iran's nuclear weapons potential by denying it the means to expand fissile material production.

That's because, despite Tehran's braggadocio, its nuclear activities are not self-sufficient. Its gas-centrifuge-based programme for uranium enrichment relies on the foreign supply of key raw materials, such as maraging steel and carbon fibre, and of critical components, including vacuum pumps, electrical subcomponents and certain kinds of measuring equipment.

This reliance is apparent from Iran's procurement efforts, as detailed by the Washington-based nuclear proliferation expert, David Albright. Iran's efforts to reverse-engineer sophisticated components have not been very successful. No wonder more than half of the centrifuges at the Natanz enrichment plant are not operating. Western-led export controls have also kept Iran from moving beyond the problematic first-generation centrifuge design obtained from the Pakistani black marketer Abdul Qadeer Khan, beginning over 20 years ago.

To build rotors for the advanced centrifuge models being tested at Natanz, Iran relies on carbon fibre rather than speciality steel. Carbon fibre is stronger and more durable. Unlike maraging steel, it can also be produced indigenously – if Iran has sufficient winding machines of the right sort. Iran's access to these winding machines is limited, however. It also, apparently, has problems obtaining other critical items that prevent it from producing advanced centrifuges in bulk.

Iran eventually may be able to overcome these technical difficulties. But progress will be slow and halting if foreign supplies remain off limits. Ali Akbar Salehi, head of the Atomic Energy Organisation of Iran, predicted last December, for example, that advanced centrifuge models will start full-scale operation by next March. On 7 July he pointed to a possible slowdown due to sanctions, acknowledging that "for some equipment like equipment for measuring, we might have some problems".

International controls are important for limiting not only Iran's uranium enrichment efforts but also its ballistic missile programme and any activities associated with production of weapons-usable plutonium, all of which fall under the UN-mandated prohibition.

The 40MW research reactor at Arak scheduled for completion in 2011 will be ideally sized for producing weapons-grade plutonium (larger than necessary for the ostensible purpose of producing medical isotopes). To extract the plutonium from the reactor's spent fuel, Iran would require reprocessing technology and speciality equipment such as manipulator arms that it now lacks, but which it could try to obtain from abroad.

Sanctions targeting Iranian vessels and aircraft can help prevent trade in such equipment. The sanctions force Iran to conduct more of its trade using foreign-flagged ships and cargo aircraft. Any attempts to transport illicit goods in foreign vessels renders them more susceptible to interdiction in accordance with international law. Whereas Iranian ships and aircraft may be unlikely to submit to demands for inspection, most foreign-flagged vessels and cargo planes will have a presumption to comply.

Iran does not have nuclear weapons and is still some time away from being able to deploy a meaningful nuclear threat should it make a decision to cross that line. The low enriched uranium that Iran has accumulated to date is sufficient to provide feed material for two nuclear weapons if further enriched. In theory, such further enrichment could be accomplished in a matter of weeks, under the right conditions. This is the worst-case breakout scenario: departure from the non-proliferation treaty and quick accumulation of highly enriched uranium

For this purpose, only one of the 164-machine cascades would need to be reconfigured; the others could be used in their current state to produce high enrichment levels in stages, with only some loss of efficiency. It will be less difficult for Iran to produce uranium at higher levels of enrichment now that it has the experience of enriching to 20%.

But Iran would still have to overcome challenges that lead western intelligence agencies to conclude that it would take Iran a year to produce the HEU for weapons. Among other challenges, Iran would have to overcome any lingering problems of metallic contamination that worsen as enrichment levels rise, causing more machines to fail. Sanctions that prevent Iran from easily replacing and improving the centrifuge machines will extend the timeline for potential weapons production.

To contain the crisis without resort to war and to prevent the theoretical possibility of a breakout scenario from becoming a stark reality, sanctions remain a key policy tool.

Mark Fitzpatrick, director of the non-proliferation and disarmament program at the International Institute for Strategic Studies and author of The Iranian Nuclear Crisis: Avoiding worst-case outcomes.