Iran’s possible responses to the assassination of a prominent nuclear scientist go well beyond boosting uranium enrichment and expelling weapons inspectors, two provisions of a law passed by Iran’s parliament that alarmed nonproliferation experts last week. Equally worrisome are new facilities the law requires, which could enable Iran to make plutonium and fashion uranium into bomb components.
The legislation had been in the works for months, but parliament fast-tracked it after the 27 November killing of Mohsen Fakhrizadeh, director of a Revolutionary Guard research unit who had previously led a secret nuclear weapons program shuttered in 2003, according to the International Atomic Energy Agency (IAEA). Iran’s powerful Guardian Council last week approved the law. The potential limits on IAEA monitoring are of particular concern, says a European diplomat involved in negotiations with Iran. “IAEA would go blind in many areas of Iran’s nuclear establishment.”
Posing a fresh proliferation risk are the new facilities the bill mandates: a lab for working with uranium in metal form—a vital skill if Iran were to make nuclear weapons—and a heavy water reactor that could accumulate plutonium in its spent fuel. “If either was to proceed, that would stand out as a major proliferation concern,” says Richard Johnson, senior director for fuel cycle and verification at the nonprofit Nuclear Threat Initiative.
Iranian President Hassan Rouhani’s administration opposed the legislation. However, Foreign Minister Mohammad Javad Zarif told an international forum last week, “We will implement it. We have no other choice.” But Zarif noted the law is reversible. “The remedy is very easy,” he said: Iran would shelve the law if the United States returns to the 2015 nuclear deal, formally called the Joint Comprehensive Plan of Action (JCPOA), which restrained Iran’s nuclear program in return for relief from economic sanctions. The Trump administration pulled out of the JCPOA in 2018; President-elect Joe Biden has pledged to rejoin it.
The JCPOA, proponents say, lengthened the time Iran would need to accumulate enough fissile material for a bomb, from several weeks to at least 1 year. A key provision is a cap on uranium enrichment at 3.67% of the fissile isotope uranium-235 (U-235), which is a level sufficient for civilian nuclear reactors. One year after the U.S. withdrawal from the JCPOA, and after Europe’s failure to deliver promised economic relief, Iran began to breach the pact, including increasing enrichment to 4.5%. A hike to 20%—which last week’s law requires—is a big step toward weapons-grade uranium, which is generally defined as greater than 90% U-235.
A heavy water reactor would pose another headache. Before the JCPOA, Iran was building a 40-megawatt heavy water reactor in Arak to produce radioisotopes for medicine. As originally designed, the reactor would have accumulated one or two bombs’ worth of plutonium each year in its spent fuel. The JCPOA required that the facility, not yet complete, be redesigned as a 20-megawatt reactor that largely eliminates plutonium production. But the redesign stalled after the U.S. Department of State in May canceled sanction waivers permitting import of necessary equipment and technology. The new law orders the Atomic Energy Organization of Iran (AEOI) to complete the 40-megawatt reactor—apparently the configuration originally planned at Arak—and design a second 40-megawatt heavy water reactor; a timetable for completion of both projects is due in early January 2021.
The law also mandates that AEOI inaugurate a “metallic uranium factory” in Isfahan within 5 months. Iran had agreed under the JCPOA to a 15-year moratorium on uranium and plutonium metallurgy.
Any provocation from the West could spur the Iranian government to implement the law even faster. “Many things could go wrong in the next several weeks,” the European diplomat says. And a U.S. return to the pact would not be instantaneous. “We can’t just snap our fingers and say, ‘We’re back in,’” Johnson says. The Biden administration would have to rescind sanctions that run contrary to the JCPOA, while Iran would have return to compliance by mothballing advanced centrifuges, for example, and steeply reducing a growing stockpile of enriched uranium.