The flag of the International Atomic Energy Agency flies in front of its headquarters in Vienna, Austria, May 28, 2015.
Heinz-Peter Bader / Reuters

Although the opponents of the 2015 Iranian nuclear deal often speak of Tehran in hyperbolic terms—as a "murderous regime" and as an exporter of “death and destruction”—their main criticism of the agreement is more mundane. It revolves around clauses known as the “sunset provisions,” which stipulate when the various restrictions imposed on Iran’s nuclear program expire and which critics say provide Iran with a patient pathway to acquiring nuclear weapons.

On September 19, Israeli Prime Minister Benjamin Netanyahu, one of the staunchest critics of the deal, which is known officially as the Joint Comprehensive Plan of Action (JCPOA), rebuked it yet again at a meeting of the United Nations General Assembly. “In a few years, [nuclear] restrictions will be automatically removed,” he said, “not by a change in Iran’s behavior, not by a lessening of its terror or its aggression—they’ll just be removed by a mere change in the calendar.” U.S. Secretary of State Rex Tillerson, although not known as the most hawkish on this issue in Donald Trump’s White House, echoed the same view later that day, saying, “The [deal’s] most glaring flaw is the sunset provision…We all know that this is merely a kick-the-can-down-the-road agreement.”

What Netanyahu, Tillerson, and other critics take issue with is not just that these expiration dates arrive too soon, but that there are expiration dates at all. Some of the deal’s prohibitions, such as on the number of Iran’s first-generation centrifuges and on the research and development of more advanced ones, are set to end in 2025, but Iran’s total enrichment capacity (less than a third of what it was prior to the deal) will remain where it is now until 2028, thanks to limits on Iran’s ability to enhance and deploy advanced centrifuges.

Other key limitations last even longer. Until 2030, the level of enrichment is restricted to 3.67 percent—far below the 90 percent needed for weapons-grade uranium. The path to a plutonium weapon is also blocked by the 15-year ban on constructing a new heavy-water reactor and on reprocessing spent fuel. 

One of the most important restrictions, the 300 kg cap on Iran’s low-enriched uranium stockpile, is in place until 2030. Iran would need 1,400 to 2,800 kg of low-enriched uranium for one nuclear weapon. This barrier renders weaponization virtually impossible until 2030.

But as the deal’s detractors point out, what then? 

The reality is that these fears are overblown. Some prohibitions continue past 2030. For instance, continuous surveillance of centrifuge production sites lasts until 2035, while the monitoring of Iran’s uranium mines and mills goes on until 2040. During that time, if and when Iran jacks up its centrifuge production or starts moving suspect amounts of uranium, the international community will know. 

Undermining the Iran nuclear deal out of fear of its sunset provisions will only achieve one thing: it will bring that sunset far closer, without a realistic and achievable alternative to prevent a nuclear-armed Iran.

Other provisions will be in place in perpetuity. For instance, Tehran is and will forever be required to notify the agency when it decides to build a nuclear facility. In contrast, under its previous safeguard agreement with the International Atomic Energy Agency (IAEA), it was only obligated to alert the international community six months before the introduction of nuclear material into the country. This was the loophole that enabled Iran to construct several undeclared nuclear facilities, which were eventually discovered in 2002 and 2009. 

Assuming the other parties to the deal reciprocate by holding up their end of the bargain, Iran will ratify in 2023 the IAEA’s Additional Protocol, which allows short-notice inspections of undeclared facilities in Iran and which it is now voluntarily implementing. To date, no country on earth has developed nuclear weapons under the watchful eyes of the IAEA’s inspectors who are empowered by the access that the Additional Protocol affords them. And of course, under the Non-Proliferation Treaty (NPT), Iran is forever prohibited from developing nuclear weapons. Of the four recent nuclear-weapon states, three (India, Israel, and Pakistan) never signed the NPT; North Korea withdrew before moving toward nuclear weapons. 

Although it is true that Iran could begin enriching uranium beyond the current 3.67 percent threshold in 2023 and will have more advanced centrifuges that will shorten the time needed to produce enough material for a nuclear weapon, without the JCPOA, Iran could start that process tomorrow. That is why scuttling the deal because of its sunset provisions is akin to committing suicide out of fear of death. 

Even a better agreement will have to contain a sunset provision. All arms control deals do. The U.S. nuclear negotiating team’s opening salvo, during the lengthy talks that led to the JCPOA, was a 20-year-long sunset for nuclear constraints and an extra ten years for intrusive inspections. Iranians wanted only two years. Months of negotiations led to a compromise and the timeline explained above. Even if the time frame were extended to 20 years, it would still be a sunset. 

The reason Iran is treated as an exception to the rule among NPT signatories—the rest of whom are legally allowed to enrich uranium and reprocess plutonium—is its past transgressions in developing nuclear facilities without informing the IAEA and conducting research on the development of nuclear weapons. The JCPOA was premised on the logic that Iran should be subjected to years of intrusive, unprecedented inspections, through which the IAEA would gain confidence in the peaceful nature of its nuclear activities. Indeed, because of the nuclear deal, there is now more comprehensive, round-the-clock remote monitoring of Iran’s nuclear sites and its one nuclear reactor than in Japan, which has 48 reactors and the largest nuclear power complex of any non-nuclear-weapons state.

Years down the road, however, when the IAEA gains confidence that there are no undeclared nuclear activities and materials in Iran, it will be unreasonable not to treat Iran like any other NPT member state in good standing. This means that the unprecedented verification measures would end, but rigorous inspections would continue in perpetuity.

If the Trump administration cannot accept this, then its real problem is not with the provisions of the deal or Iran’s compliance with them. It is, rather, either with the NPT itself or with the nature of the Iranian political system. If so, no deal would be satisfactory, unless it entails Tehran’s total capitulation to U.S. demands or a regime change. Neither appears in the cards.

Undermining the existing nuclear deal with Iran in the hope of achieving an illusory one that contains permanent restrictions will do nothing to address critics’ alleged concerns over the JCPOA’s sunset provisions because Tehran would never accept such terms. If the United States wants longer and stronger constraints, it would be better off trying to do something that at least has a chance of succeeding—for example, marshaling international support for a plan to apply the agreement’s limitations on uranium enrichment and plutonium separation either regionally or internationally for a long period of time. Washington could also encourage joint ventures for uranium enrichment and other nuclear fuel cycle activities involving other countries that would provide added assurance that Tehran’s nuclear program remains civilian. Finally, the United States must live up to its obligations to the deal today in order to make any potential follow-on agreements possible tomorrow.

Undermining the Iran nuclear deal out of fear of its sunset provisions will only achieve one thing: it will bring that sunset far closer, without a realistic and achievable alternative to prevent a nuclear-armed Iran.

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