Per ISIS – As of November 2021, Iran had enough enriched uranium hexafluoride (UF6) in the form of near 20 and 60 percent enriched uranium to produce enough weapon-grade uranium (WGU), taken here as 25 kilograms, for a single nuclear weapon in as little as three weeks. It could do so without using any of its stock of uranium enriched up to 5 percent as feedstock. The growth of Iran’s stocks of near 20 and 60 percent enriched uranium has dangerously reduced breakout timelines.
The Institute for Science and International Security is a non-profit, non-partisan institution dedicated to informing the public about science and policy issues affecting international security. Its primary focus is on stopping the spread of nuclear weapons and related technology to additional nations and to terrorists, bringing about greater transparency of nuclear activities worldwide, strengthening the international non-proliferation regime, and achieving deep cuts in nuclear arsenals.
Iran could detonate a nuclear explosive underground in as little as six months, rattling the Middle East profoundly, destabilizing the region perhaps irretrievably.
Although Iran would need longer to field a credible, reliable nuclear-tipped ballistic missile, it knows enough to build a nuclear explosive and build an underground nuclear test site. While most of the public focuses on deliverable nuclear weapons, many lose sight of Iran’s extensive knowledge and experience in building nuclear weapons and the immense damage resulting from a nuclear explosion.
Iran is mastering the construction and operation of advanced centrifuges far faster than anticipated.
Iran has rapidly increased its number of advanced centrifuges, so far doubling the number from before the JCPOA and planning to triple the pre-JCPOA quantity over the next several months. The most important advanced centrifuges today are the IR-2m, IR-4, and IR-6 centrifuges. Because of their far greater enrichment outputs, they are more useful in a speedier breakout to weapon-grade uranium or a more difficult to detect sneak out in a clandestine enrichment plant.
In January, 2018, the Israeli Foreign Intelligence Service Mossad broke into a warehouse in Tehran and seized a large cache of documents detailing Iran’s darkest and long-denied secret. The Amad Plan, the codename for its crash nuclear weapons program, was far larger and made much more progress than previously known. Containing many top secret details, the seized documents offer unprecedented insights into Iran’s progress—and the hurdles it faced in building nuclear weapons.
Iran had accumulated enough information and experience by the end of the Amad Plan to be able to design and produce a workable implosion nuclear device. This device benefited from a relatively compact high explosives initiation system, the shock wave generator, and a specialized neutron initiator. The nuclear weapon design has a diameter roughly the same as a car tire.
By the end of the Amad Plan, Iran was preparing to conduct a cold test of a nuclear explosive, typically the last step before building a prototype nuclear explosive and then making nuclear weapons.
About half of the facilities in the Amad Plan were undiscovered or unknown until after the seizure of the Iranian Nuclear Archive in 2018.
Iran decided under the Amad Plan that it would use low-enriched uranium from Natanz for further enrichment to weapon grade uranium at what is now known as the Fordow site.
Iran’s decision to halt the Amad Plan merely served as a tactical retreat, not an abandonment of its nuclear weapons ambitions or activities, a step taken earlier by other countries, notably Taiwan and South Africa.
Three of the five key leaders of the Amad Plan and post-Amad organizations have died violent deaths. Two others narrowly escaped death.
The Institute’s 2021/2022 Peddling Peril Index (PPI), the only public effort to comprehensively rank national strategic trade control systems ranks Iran as 196 out of 200, clustered with the likes of North Korea, South Sudan, and Yemen.
Highly Enriched Uranium Production
Stocks of enriched uranium are easily blended down or shipped out of Iran, allowing the reestablishment of the JCPOA’s enriched uranium limits. Yet, this is not the case regarding Iran’s newly gained experience in making highly enriched uranium.
Iran has been producing 60 percent HEU, the closest in enrichment level it has got so far to 90 percent enriched uranium, or weapon-grade uranium, the most desirable enrichment level for nuclear weapons and a short dash from 60 percent material. Since it started producing at this enrichment level in April 2021 until the end of August, Iran generated a stock of 10 kilograms (uranium mass) or 14.8 kg (uranium hexafluoride (UF6) mass) of 60 percent enriched uranium, and at the end of August, it was increasing this stock at the rate of 2.3 kg per month (uranium mass).20
This amount of HEU could be further enriched to 90 percent in one centrifuge cascade in a few short weeks or even days if two cascades were used. Upgrading to weapon-grade is quick, because in terms of separative work, production of 60 percent enriched uranium represents 99 percent of the work needed to produce weapon grade uranium. Moreover, this enrichment to weapon-grade could proceed in parallel to other centrifuge cascades further enriching near 20 and five percent enriched uranium up to the level of weapon-grade. In this manner, Iran is further shortening its breakout timelines. The production of ten kilograms of 60 percent in effect allows a 20-25 percent reduction in breakout timelines, compared to a situation of only possessing up to 5 and up to 20 percent enriched uranium.
Often lost in the debate is that 60 percent enriched uranium can be used directly in a nuclear explosive, although 90 percent HEU, or WGU, is preferred, because less material is needed for a given explosive yield. In terms of a simple extrapolation from 25 kg of weapon-grade uranium, Iran now has about one quarter of what it would need to produce one nuclear explosive fashioned from 60 percent HEU, factoring in losses and known Iranian nuclear weapon capabilities. With further design improvements, significantly smaller amounts of 60 percent enriched uranium would suffice, but Iran’s past, known nuclear weapons efforts have not demonstrated a capability for such significant reductions in total mass. Adding in expected losses, a reasonable estimate for Iranian capabilities would settle on the 40 kg value, with a recognition that less is possible, as with the case of weapon-grade uranium.
While a new deal would be expected to require the elimination of this dangerous HEU stock, its production has enabled Iran to learn critical information about producing HEU in its cascades. Overall, Iran must be recognized as able to breakout faster and more efficiently than it could do prior to these accomplishments.
For example, Iran has experimented with faster, more efficient production of 60 percent HEU, starting with 5 percent enriched uranium. It has learned how to skip a traditional enrichment step, making the production of HEU more efficient. Iran is learning how to use a cascade declared for production of low enriched uranium to make HEU, without conducting noticeable cascade re-configurations. This advancement may mean that Iran can now make 90 percent enriched uranium directly from 20 percent enriched uranium.
Iran is also practicing re-enriching tails from 60 percent production, resulting in new feedstock that can be more easily and efficiently reused, contributing further to more efficient HEU production and reduced breakout timelines for the production of successive weapon’s quantities of weapon-grade uranium.
Moreover, the 60 percent HEU can stand in for weapon-grade uranium hexafluoride during production, handling, and storing. Further, along with 20 percent enriched uranium, the 60 percent enriched uranium could provide an important surrogate material for weapon-grade uranium during conversion experiments, metallurgy, or weaponization tests.
SOURCES – Institute for Science and International Security