资源环境科技发展态势分析平台

Ratcheting up its maximum pressure campaign on Iran, the U.S. State Department will no longer waive sanctions against parties redesigning an Iranian heavy water reactor to sharply curtail its generation of plutonium, which can be used to build nuclear weapons.

The 27 May decision is “tremendously concerning,” says Jeffrey Lewis, director of the East Asia Nonproliferation Project at the Middlebury Institute of International Studies at Monterey. “Heavy water reactors are a substantial proliferation concern.”

Under the 2015 nuclear deal, formally called the Joint Comprehensive Plan of Action (JCPOA), the United States and other Western powers agreed to relax sanctions on Iran if it dismantled large pieces its nuclear program and thereby eliminated pathways for quickly building nuclear weapons. In May 2018, the Trump administration withdrew from the agreement, arguing it didn’t go far enough. Other signatories sought to salvage the JCPOA, but flagging efforts prompted Iran, among other steps, to ratchet up uranium enrichment and take other steps it has characterized as reversible.

Even as the agreement unraveled, the United States renewed waivers that permit other parties to cooperate with Iran on civilian nuclear activities without running afoul of U.S. economic and legal sanctions. But Secretary of State Mike Pompeo now says waivers for three projects—the conversion of the Arak heavy water reactor, the provision of enriched uranium fuel for the Tehran Research Reactor, and the removal of spent and scrap reactor fuel from the Tehran reactor—will end on 27 July. A single waiver will remain in place, for now: international cooperation to ensure the safety of Iran’s Bushehr Nuclear Power Plant, and Russia’s provision of fuel for the reactor.

Nonproliferation experts are especially surprised at the decision to pull the rug out from the effort to redesign the Arak IR-40 heavy water reactor. As originally designed, the reactor would burn natural uranium, which would generate enough plutonium in its spent fuel to produce one or two bombs per year. Early on in JCPOA negotiations, the focus was on dismantling Iran’s uranium enrichment facilities, and when the outline for a deal was announced in Geneva, “The French were really upset because it didn’t include [limits on] the plutonium production at Arak,” Lewis says. That set alarm bells ringing in Israel. “They didn’t want to see a plutonium reactor in their backyard,” says Richard Johnson, senior director for fuel cycle and verification at the nonprofit Nuclear Threat Initiative.

In the end, Iran agreed to convert Arak to run on low-enriched fuel, which would produce only traces of plutonium. As a first step, in January 2016, workers removed the IR-40’s calandria—the vessel holding the reactor core—and filled it with concrete. A China-U.S. working group set about designing a new reactor. “We didn’t want the IR-40 to sit around empty,” says Johnson, who was the lead U.S. representative to the working group. “We were trying to build a new design into that old framework.”

The goal was to complete the conversion within 5 or 6 years. “The Iranians were eager to do this even faster,” Johnson says. But negotiations between Iran and China, which would take the lead on building the new reactor, took longer than expected, and construction work has not yet begun. “I cannot stress enough how bizarre it is to me that we demanded that the Iranians convert the reactor—and now we insist they must not convert it,” Lewis says.

Ultimately, politics trumped nonproliferation. “The arguments against maintaining any vestiges from the JCPOA have won the day,” says Naysan Rafati, senior analyst on Iran at the International Crisis Group. With the U.S. presidential election coming up in November, observers don’t expect Iran to move quickly to scrap its commitment to a proliferation-resistant design for Arak. However, “We can’t count on the Iranians to always be the reasonable party,” Lewis says. “At some point, a critical mass in the Iranian leadership will lose patience.”