It’s unclear when Iran might get the bomb. In July, Secretary of State Blinken revealed that Iran was only one to two weeks away from producing enough weapons grade uranium for several bombs. The New York Times quoted experts who estimated it would take Iran up to another year to make a missile-deliverable weapon. A conservative estimate would be no more than five months but could be much less.
In the attached historical analysis of China’s nuclear weapons program, Hui Zhang pegs the number at three to five weeks, and possibly less. It makes for interesting reading, not only on what China was able to accomplish so quickly sixty years ago, but on what Iran may do.
You can access a full copy of the paper below. As always, I’m interested to get your take.
December 12, 2024
Author: Hui Zhang
Editor: Henry Sokolski
Lessons from China: How Soon Could Iran Get the Bomb?
By Hui Zhang
Once Iran acquires enough weapons grade uranium, how quickly could it make a bomb? Some nuclear experts argue it would take Iran many months or possibly as long as a year to make a nuclear weapon.[1] However, the history of China’s nuclear weapons programs shows that Tehran could build a bomb in just three to five weeks.
There are other crucial steps needed to make a warhead aside from acquiring the necessary fissile materials. It would take additional time to convert uranium hexafluoride gas (UF6) to metallic form, and then to cast and machine the metal into the core of a bomb. Meanwhile, other non-nuclear components would need to be ready to assemble a complete warhead.[2] Those non-nuclear components would include a weapon design, a neutron initiator, a detonation wave focusing system, high explosives, detonators, and an arming, fusing, and firing (AF&F) system.
However, as proven by the experience of other nuclear weapon states, non-nuclear components can be built in parallel with the production of nuclear weapons fuel. In fact, when China produced its first batch of highly enriched uranium (HEU) (93.5 percent U235) in January 1964 (enough for two bombs) for the October 1964 nuclear test, all the non-nuclear components needed for those two bombs had been accomplished by 1963.[3] At that time, the weaponeers were just waiting on HEU production to complete the weapon. As detailed in following sections, once China’s scientists had sufficient HEU, they spent three to five weeks converting uranium hexafluoride gas (UF6) to metallic form, purifying, and then casting. They fabricated the first bomb core (made of two hemispheres) on the early morning of May 1st, 1964, after spending about ten hours with manually operated machining tools.[4] In early August, they started the final assembly process of the two bombs. By August 20th, 1964, they assembled the two bombs with carefully subcritical measurements at the Qinghai nuclear weapon plant.[5] It took only about three days to assemble the first bomb.[6] After initial assembly, they disassembled the two bombs to prepare them for shipping to the Lop Nur test site at Xinjiang. The bomb was then reassembled in about ten hours at the Qinghai site and prepared for China’s first nuclear explosion. Thus, from converting UF6 to assembling a finished atomic bomb, China only took about three to five weeks.
China’s case happened 60 years ago, when China lacked advanced equipment. If China’s scientists had been under a tightened schedule or pressured during war time, its three-to-five-week timeframe would likely be even shorter. In the case of the Manhattan Project, U.S. scientists took only nine days after producing enough HEU materials to finish the metallic HEU components for the core (of 60 kg HEU) of the Little Boy bomb on July 24th, 1945. The United States detonated Little Boy over Hiroshima on August 6th, 1945, only 13 days later.[7]
Portions of Iran’s “nuclear archive,” which Israel seized in January 2018, clearly show Iran’s weaponization projects running in parallel with HEU projects under the “Amad Plan” — Iran’s code name for its crash nuclear weapons program between the 1999 and 2003. The Amad Plan aimed to produced five nuclear weapons by early 2004, including four deliverable warheads for the Shahab-3 missile, and another one for testing underground.[8] On April 30th, 2018, Prime Minister Benjamin Netanyahu presented Iranian documents showing Iran’s intention to build five 10- kiloton, ballistic missile-deliverable nuclear warheads.[9]
In 2003, Iran halted work on all aspects of its weapon program except the production of fissile materials. Iran’s nuclear archive reveals that, by this time, Iran had already made substantial progress on almost all other aspects of nuclear weaponization, including weapon design (see Appendix B), neutron initiator (see Appendix C), detonation wave focusing system, (see Appendix D), “cold” testing (see Appendix E), casting and machining (see Appendix F), and integration of warheads and reentry vehicles.[10]
Even if some of the major non-nuclear components were not completed during the Amad Plan, Iran has probably made significant progress on those unfinished projects in the last 20 years. As discussed in the following sections, China’s case demonstrates that non-nuclear weapon components tasks can be completed within one to two years. In fact, after the closure of the Amad Plan in 2003, other Iranian organizations continued to work on nuclear weapons programs with a smaller, more dispersed effort. As David Albright and Sarah Burkhard concluded, “the evidence suggests that Iran not only maintained the capability to produce nuclear weapons, but actively worked on efforts to advance that capability in case Iran’s leaders made a decision to build them.”[11]
Although it is unclear how much effort Iran has put into its weaponization programs since 2003, Iran likely sped up its weaponization efforts after the JCPOA failure in 2018. There were two whole years between the dissolution of the JCPOA and the murder of Iran’s top nuclear weapons program leader, Mohsen Fakhrizadeh, who led the program from 1998 until his death in November 2020. It’s possible Iran made significant progress during that two-year period.
Since 2022, Iranian officials have spoken openly about nuclear bomb prospects. This is a departure from a fatwa issued in 2003 by Iran’s Supreme Leader Ayatollah Ali Khamenei, which banned the possession of nuclear weapons. In July 2022, Kamal Kharrazi, an adviser to Supreme Leader Khamenei, stated that, “in a few days we are able to enrich uranium up to 60 percent and we can easily produce 90 percent enriched uranium. … Iran has the technical means to produce a nuclear bomb but there has been no decision by Iran to build one.”[12] Recently, as Iran inches closer to a HEU production “breakout,” discussions about nuclear weapons inside Iran are even louder. In February 2024, Ali-Akbar Salehi, the former chief of Iran’s Atomic Energy Organization, claimed that Iran already had “all the pieces” necessary for a bomb.[13] In April 2024, Javad Karimi Ghodousi, a member of the Iranian parliament’s National Security Commission, declared that if the supreme leader “issues permission, [Iran] would be a week away from testing [its] first [nuclear bomb].” [14]
Indeed, if all other non-nuclear components are ready, the time between acquiring enough HEU to assembling a working bomb can be as short as a few weeks. This timeline is clearly demonstrated with China’s first bomb case and the case of America’s Little Boy bomb. The most time-consuming aspect of the bomb-building process is metal melting and casting. Iran has already started laying the groundwork for this project. Iran started preparatory work on converting HEU fuel into a bomb core during the Amad Plan. According to IAEA reports, Iran started uranium metal converting work at the Fuel Fabrication Plant in Esfahan in 2021.[15] While Iran plans to use these metals to fuel its research reactor, the experience gained from such activities would surely help an Iranian weapon program. (For more information on Chinese and Iranian uranium metal components production, see Appendix F.)
Prior to signing the JCPOA in 2015, the U.S. government assessed Tehran had not mastered the necessary technologies to build a nuclear weapon. In July 2024, however, the U.S. Office of the Director of National Intelligence (ODNI) determined that Iran had “undertaken activities that better position it to produce a nuclear device, if it chooses to do so.”[16] This new ODNI assessment suggests Iran has significantly advanced its nuclear program over the last several years. In a press conference on July 31st, 2024, Sen. Lindsey Graham warned, “… I believe it is a certainty that if we do not change course, Iran will in the coming weeks or months possess a nuclear weapon.”[17]
While there’s no evidence that Iran has made up its mind to build a bomb, the weakening of its deterrence against Israel’s attacks, as shown recently by the damage inflicted on its ally, Hamas, and militia, Hezbollah, may motivate Tehran to pursue a nuclear deterrent.[18] If Iran makes such a decision while facing the pressure of Israeli or American strikes on its nuclear facilities, Tehran would be able to make its bombs quickly and secretly.
To read the full paper, click here.
Footnotes