The science behind the Iranian nuclear deal: why Iran is open for business but not a bomb

Talks in Switzerland in late March. Brendan Smialowski/Reuters

Marathon bargaining sessions aimed at curbing Iran’s nuclear program between Iran and the US, UK, Germany, France, Russia and China finally ended earlier this month, culminating in a set of key parameters to be negotiated for a final agreement.

The details of the parameters differ among the participants. The US released a factsheet describing the arrangement in great detail – even including a schedule – while Iran and the EU presented a joint statement that is consistent with the factsheet but devoid of numbers or explicit information.

When the parameters of the agreement became public, many analysts were pleasantly surprised. If a deal is completed, Iran will be able to keep all of its facilities open, but Iran’s nuclear program will be significantly curtailed and the International Atomic Energy Agency (IAEA) will be given sufficient access to verify the agreement.

The problem with a nuclear energy program producing fuel from scratch is that it can easily hide a nuclear weapons program, which the West has long suspected, but Iran has steadfastly denied that this is their objective.

To restrict Iran from developing atomic bombs, the proposed deal includes a number of restraints on Iran’s technical facilities. Those measures are designed to limit production from its nuclear facilities to only medical uses and domestic energy production.

What analysts fear

Most nuclear reactors use uranium fuel enriched in centrifuges. Centrifuges are machines that increase the proportion of the useful form, or useful isotope, of uranium to 3–5% relative to all other uranium isotopes present.

To create enriched uranium, uranium ore is chemically processed, converted into a gas and loaded in centrifuges, which spin the material at high speed. In centrifuges, a tiny difference in weight between the useful and less-useful isotopes separates the two types to create higher enrichment.

The problem is that only a small quantity of gas can be loaded in centrifuges, and the enrichment capabilities of Iran’s centrifuges are low. This is why Iran currently has a colossal number of centrifuges installed – estimated by IAEA officials to be 19,000 – and is spinning half of them to enrich uranium.

What most analysts fear is that gas already enriched 3%-5% for the reactor fuel program could be enriched further to be useful for a bomb. Generally, fuel for most nuclear power plants is enriched 3%-5% – that is, the uranium has that percentage of the desired isotope in it. Weapons-grade material typically is enriched to more than 90%.

The crucial point is that the same equipment used to enrich uranium for nuclear power plant reactors can be used to enrich uranium to weapons-grade, and the process is not linear. Once a certain quantity is enriched for reactors, it only takes a little bit more effort to enrich that quantity to a level useful for nuclear weapons.

Imagine the process of enrichment to weapons-grade as running a marathon. Gas enriched to 5% is comparable to starting the marathon with an 18-mile head start: there are only a few more miles to reach the finish line of highly enriched uranium of more than 90%.

To respond to this concern, Iran will have a two-thirds overall reduction in centrifuges at its main site, Natanz, and its underground site at Fordow. The quantity and level of enrichment kept in Iran will also be limited, stretching the time to enrich enough uranium gas for a bomb to one year, while still allowing Iran to produce some fuel for its reactors. The situation now is thought to be about two to three months – the so-called breakout time.

A 2013 profile of Iran’s nuclear centrifuges. The centrifuges spin uranium gas at high speeds to enrich it for use in energy, medicine or weaponry. Reuters Graphics

In addition, Fordow will be used solely for enrichment of other elements, not uranium, and will become a nuclear physics and technology center. For example, centrifuges will probably be used to enrich certain isotopes of the element molybdenum as part of the process to produce an isotope used in 80% of all nuclear medicine procedures worldwide.

Both the factsheet and the joint statement lack detail on Iran’s extensive centrifuge research and development program. Iran will have to dismantle many of its centrifuges that are used for production, but the agreement is not clear about what will happen to research on its next-generation centrifuges, which could produce enriched uranium much faster.

Then there’s plutonium

Another route for producing a nuclear bomb is to use plutonium, which is produced in all uranium-fueled reactors.

The best-quality plutonium for a bomb is produced in heavy-water reactors like the Iranian Arak reactor, the development of which has been frozen since the negotiations started in early 2014. In fact, India, Pakistan, and Israel have all used similar heavy-water reactors to produce plutonium for their weapons programs.

The EU statement and US-produced factsheet both stated that Iran has agreed to redesign the reactor so that it will not produce weapons-grade plutonium. And the fact sheet stated that Iran will commit to using the reactor solely for medical isotope production.

Plutonium is extracted from the used nuclear fuel through a chemical separation process called reprocessing, requiring elaborate industrial-scale facilities. As a further step meant to reduce risk, Iran has agreed on three actions: it will not build such reprocessing facilities, engage in reprocessing, and it will ship all used fuel out of the country after it is removed from the reactor.

If an agreement that adheres to the key parameters is realized, it could potentially be a new start for a responsible nuclear-energy program for Iran, and it could herald a new era of international cooperation in the region.