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SECTION 1: Background and Status of Iran’s Nuclear Program
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The agreement reached between Iran and the P5+1 (China, France, Germany, Russia, the United Kingdom, and the United States) on November 24, 2013, was a significant breakthrough after a decade of negotiations to resolve international concerns about Tehran’s nuclear program.

Prior to this historic agreement, Tehran had been steadily improving its capability to produce fissile material for nuclear weapons. Serious questions about Iran’s past activities related to developing nuclear weapons also remained unanswered.

Although the U.S. intelligence community assesses that Iran abandoned a coordinated nuclear weapons program in 2003, the 2007 National Intelligence Estimate (NIE) on Iran and more-recent intelligence community testimony assessed that Iran has developed a range of technologies, including uranium enrichment, nuclear warhead mechanics, and delivery systems, that would give it the option to launch a nuclear weapons development effort in a relatively short time frame “if it so chooses.”[1]

Such an effort is not the same as a crash program designed to construct a nuclear weapon as soon as possible, which would require that Iran eject inspectors and try to produce weapons-grade material at its declared facilities or perhaps at undeclared facilities before such an effort could be detected and disrupted.

Instead, Tehran appeared to be taking a more deliberate approach, building up as much of its technological base as possible for what is ostensibly a peaceful nuclear energy program while reserving the option to make a political decision to build and deploy nuclear weapons.

As Director of National Intelligence James R. Clapper explained in his 2012 testimony, “We judge Iran’s nuclear decision making is guided by a cost-benefit approach, which offers the international community opportunities to influence Tehran.”[2]

Iran’s Nuclear Ambitions and Capabilities

Iran’s interest in pursuing an ambitious nuclear power program preceded the 1979 revolution. The United States provided a kick-start to Iran’s nuclear program by signing a nuclear cooperation agreement under President Dwight Eisenhower’s Atoms for Peace Program in 1957 and subsequently provided the five-megawatt-thermal (MWt) Tehran Research Reactor. The shah’s government later announced plans for building more than 20 nuclear power reactors for generating electricity.[3]

Beginning with the first serious discussions with Tehran in the 1970s about helping to construct nuclear power reactors, the U.S. government sought to impose safeguards beyond those required by the nuclear Nonproliferation Treaty (NPT). For his part, the shah pushed hard for domestic development of the full nuclear fuel cycle, in particular the ability to reprocess spent fuel.[4] Although Iran claims today that Washington accepted a robust nuclear power program in Iran under the shah, the United States insisted at the time that Iran not possess a reprocessing capability due to fears it would be used to produce plutonium for nuclear weapons.[5]

After a brief interregnum following the 1979 revolution, the Iranian government resumed its pursuit of the previous regime’s nuclear aspirations, albeit slowly, as Ayatollah Ruhollah Khomeini initially opposed nuclear development for theological reasons. Following Khomeini’s death in 1989, the new supreme leader, Ayatollah Ali Khamenei, expanded Iran’s undeclared nuclear activities.[6] The nuclear capabilities that Iran has been pursuing can be used for a peaceful nuclear energy program and nuclear weapons development, although some of the capabilities on which Iran has focused strongly suggest an intention to have the option to build weapons.

Steps to Building Nuclear Weapons

The most recent U.S. Intelligence Community assessment of Iran’s nuclear weapons potential, as expressed by Director of National Intelligence James Clapper in testimony before Congress in January 2012, is that: Tehran has made technical progress in a number of areas—including uranium enrichment, nuclear reactors, and ballistic missiles—from which it could draw if it decided to build missile-deliverable nuclear weapons. These technical advancements strengthen our assessment that Iran has the scientific, technical, and industrial capacity to eventually produce nuclear weapons.

There are two routes for Iran (or any state) to obtain sufficient fissile material to make nuclear weapons—using highly enriched uranium or plutonium. The following major scientific, technical, and industrial steps are required to build a uranium or plutonium weapon.

Mining or Importation of Uranium Ore

Iran is believed to have large reserves of uranium and two working mines.

Milling of Uranium

Concentrating uranium from ore, i.e., increasing uranium oxide content to 65-85 percent to produce “yellow cake.”

Processing (Conversion)

Converting yellow cake, a solid, into uranium hexafluoride, a gas.


Increasing the relative abundance of the uranium-235 isotope in the uranium hexafluoride

  • to light-water power-reactor grade (3.5 percent)
  • to research-reactor grade (20 percent)
  • to weapons grade (90+ percent)

The IAEA estimates that 25 kg of weapons grade uranium is sufficient to produce one nuclear device.


A nuclear “heavy water” reactor fueled by natural uranium will produce plutonium as a byproduct of reactor operatons. The plutonium must be separated from the spent fuel and the highly radioactive fission product contained in the fuel.

Spent Fuel Reprocessing

A separate reprocessing facility is needed to separate out the plutonium before it can be used in nuclear weapons.

The IAEA estimates that 8 kg of weapons-grade plutonium is sufficient to produce one nuclear device.


Converting weapons-grade uranium hexafluoride to uranium dioxide powder and into metallic forms for use in the fissile core of a nuclear device, or fabricating plutonium weapons components from reprocessed fuel.

Weapons Design and Assembly

Designing and assembling the other non-nuclear components in and around the fissile material core to make a device capable of forming the “physics package” of a warhead, suitable for use as part of a combat-ready weapons system.

Nuclear Explosive Testing

Detonating the nuclear device as proof of concept. Typically, multiple nuclear test explosions are necessary to perfect warhead designs, particularly smaller, lighter, more efficient designs.

Weapons Integration With a Delivery System

Adapting the warhead for placement into a bomb or the nose cone of a delivery vehicle.

Missile Testing With Inert Warhead

Performing flight tests with an inert warhead to confirm the performance of the non-nuclear functions of the warhead, such as safing, arming, and fusing, which are necessary in order to achieve higher levels of confidence and reliability.

Iran’s interest in developing a nuclear weapons capability is directly aligned with the central priority of its leadership: the survivability of its regime. The Islamic republic’s revolutionary government has seen itself under threat since it came to power in 1979 because of Tehran’s adversarial relationship with the United States and from the bitter eight-year war with Iraq, which invaded Iran in 1980.

Although Iran’s former primary adversary in Baghdad has been replaced by a friendlier government, the presence of U.S. forces in Afghanistan and Iraq likely heightened Tehran’s concerns about the external threat posed by the United States. Tehran’s national security aims are grounded in deterring threats to the regime.

According to a 2010 Pentagon report on Iran’s military power, “Iran’s nuclear program and its willingness to keep open the possibility of developing nuclear weapons is a central part of its deterrent strategy.”[7] Subsequent reports found that Iran “is developing a range of technical capabilities that could be applied to the production of nuclear weapons if the decision is made to do so.”[8]

Iran’s nuclear ambitions also are rooted in the country’s goal of exerting influence throughout the region. Tehran’s military power is not proportionate to its economic power, however, and its conventional military capabilities are limited by lack of training and modern weaponry. Iranian military modernization also has been constrained since the days of the Iran-Iraq war because of limited access to foreign weapons and parts.

Consequently, although Iran has been active in building a domestic arms industry, it still retains U.S.-built weapons from the time of the shah and lower-quality, Russian- and Chinese-built systems acquired in more recent years. Iran has vigorously pursued the development of ballistic missiles, many of which are capable of delivering nuclear weapons in the region.

Any decision by Iran’s leadership to pursue nuclear weapons development would need to overcome significant political and technical hurdles. Iran has long said that its nuclear program is exclusively for peaceful purposes. Additionally, there is religious opposition to the development of weapons of mass destruction. Khamenei has called nuclear weapons a “grave sin,” claiming that Iran “has never pursued and will never pursue” them.[9]

Iran’s apparent work on developing a nuclear warhead, at least prior to 2004, undermines Khamenei’s declarations; Iran would need to find some way to explain the reversal of its stated policy to Iranian domestic audiences and the international community.

Major countries and rising powers, such as China, Russia, India, and Brazil, which have been reluctant to apply heavier pressure on Iran so long as it is not obviously pursuing weapons development, would not be able to maintain close relations with Tehran in the event of an open decision by Iran to build nuclear weapons. Iran would suffer even greater political, economic, and very likely military consequences of any such decision.

Today, the most relevant aspects of Iran’s nuclear program for a nuclear weapons option are its uranium-enrichment-related facilities, its heavy-water reactor activities, and the work it has carried out on warhead development.

These and other activities must be addressed in a comprehensive deal in a way that increases the time it would require Iran to amass fissile material for nuclear weapons and in a way that reduces the time it would take to detect and disrupt any such efforts. Over time, the agreement must help increase confidence from the international community that Iran is engaged in an exclusively peaceful nuclear program.

Uranium Enrichment

For more than a decade, Iran’s uranium-enrichment program has been the focus of international concern about Iran’s nuclear aspirations because it provides Iran with the ability to produce one form of fissile material for nuclear weapons: weapons-grade highly enriched uranium (HEU).

The uranium pathway is the most likely route that Iran would use to produce fissile material for nuclear weapons, if the decision was made to pursue them. Iran enriches uranium using a machine called the gas centrifuge, which spins at very high speeds to increase the concentration, or percentage, of the fissionable isotope uranium-235.

Centrifuges are organized in groups called cascades, which generally contain either 164 or 174 machines and produce uranium enriched to different levels. Uranium enriched to less than 5 percent U-235 is typically used to fuel nuclear power plants. Research reactors, such as the Tehran Research Reactor, often run on uranium enriched to 20 percent. Uranium enriched to less than 20 percent is referred to as low-enriched uranium (LEU). Nuclear weapons require HEU, which typically has greater than 90 percent U-235.

Beginning in the mid-1980s, Iran acquired gas centrifuge technology through the nuclear smuggling network led by former Pakistani nuclear official Abdul Qadeer Khan, who provided similar assistance to Libya and North Korea. The centrifuge model that Iran is using to enrich uranium, the IR-1, is based on a Pakistani design, the P-1. The P-1 design was originally smuggled by the Khan network from the European enrichment consortium URENCO in the 1970s.

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Iran currently enriches uranium at two sites, Natanz and Fordow. Iran has manufactured more than 20,000 centrifuges domestically for these facilities, but is unlikely to be able to produce indigenously all of the materials, such as high-quality carbon fiber and maraging steel, necessary to expand its nuclear program. Tehran continues to rely on illicit networks to bypass international sanctions prohibiting the purchase of these materials. This dependency on foreign suppliers has slowed Iran’s production of centrifuges.

Despite the supply constraints, prior to the November 24, 2013, interim agreement, Iran’s centrifuge capacity was gradually increasing as it continued to install more IR-1 machines at both facilities and develop advanced models for Natanz.

The Natanz plant is Iran’s primary uranium-enrichment facility. An Iranian opposition group, the National Council of Resistance of Iran, revealed in August 2002 that Iran was building the facility. In February 2003, Iran officially acknowledged the existence of Natanz and allowed the International Atomic Energy Agency (IAEA) to visit the facility. At that time, Iran had about 100 centrifuges installed in a pilot cascade.

The Natanz site comprises an industrial-scale enrichment facility, the Fuel Enrichment Plant, which is intended to eventually house about 50,000 centrifuges, and the Pilot Fuel Enrichment Plant. The Pilot Fuel Enrichment Plant is a research and development facility where Iran is testing more-advanced models of centrifuges, including the IR-2M, IR-4, IR-5, IR-6, and IR-6S, to replace the crash-prone IR-1 models. Progress on the advanced machines has been slow. It is unclear which model Iran may choose to deploy, when it would be capable of doing so in large numbers, and how their efficiency measures against the IR-1. In December 2013, Iran announced it would begin testing a new model, the IR-8, which it claimed to be 15 times more efficient than the IR-1. Yet, the IAEA reported in May 2014 that this centrifuge had not been tested.

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Prior to the November 24 Joint Plan of Action, Iran had installed 15,420 IR-1 centrifuges at the Fuel Enrichment Plant, of which approximately 9,200 are operational in 54 cascades. The IR-1 machines are currently enriching uranium to 3.5 percent.

In January 2013, Iran informed the IAEA that it planned to install IR-2M machines in production-scale cascades at the Natanz Fuel Enrichment Plant. Prior to the November 24 agreement, Iran had installed 1,008 advanced IR-2M centrifuges there. These centrifuges are not yet enriching uranium.

Experts assess that, when operational, the centrifuges will be three to five times more efficient than the IR-1 centrifuges. Based on the design information provided to the IAEA, Iran wants to install approximately 3,000 IR-2M centrifuges in this area of the facility. According to the Atomic Energy Organization of Iran, these centrifuges would produce uranium enriched to 3.5 percent.

Prior to the November 2013 interim agreement, Iran had produced about 11,100 kilograms of 3.5 percent-enriched uranium, an amount sufficient for several nuclear weapons if enriched further to weapons grade and then fabricated into the weapons’ metallic cores. About 3,500 kilograms was further enriched to 20 percent. This left about 7,600 kilograms of 3.5 percent-enriched uranium in the stockpile in November 2013. As of May 2014, the IAEA reported that the stockpile of uranium enriched to 3.5 percent was 8,474 kilograms.

In February 2010, Iran began producing uranium enriched to 20 percent in two cascades of IR-1 centrifuges at the Natanz Pilot Fuel Enrichment Plant. In January 2012, Iran also began enriching uranium to 20 percent at its Fordow plant, using 696 IR-1 centrifuges in four cascades. Enrichment to a level of 20 percent was halted under the November 2013 Joint Plan of Action, and the cascades at each facility now produce uranium enriched to 3.5 percent.

The Fordow facility is located inside a mountain bunker and was built in secrecy, but in September 2009, France, the UK, and the United States publicly revealed its existence. Iran is believed to have informed the IAEA about the plant’s existence only after discovering that Western intelligence agencies had learned of it.

An additional 11 cascades containing approximately 1,900 IR-1 centrifuges are installed at Fordow, but are not operating. An additional cascade remains incomplete. The facility now contains almost its full design capacity of nearly 3,000 machines in 16 cascades.

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In total, as of January 2014, Iran has produced 447 kilograms of 20 percent-enriched uranium. Dating back to 2012, however, Iran has withdrawn approximately 303 kilograms of the 20 percent-enriched uranium hexafluoride gas for conversion into uranium oxide, a solid, at the Esfahan Fuel Plate Fabrication Plant. The uranium oxide is 20 percent-enriched material in the form of a powder used to produce fuel plates for the Tehran Research Reactor.

In January 2014, when the Joint Plan of Action began to take effect, the IAEA reported that Iran had a stockpile of about 209 kilograms of 20 percent-enriched uranium material in gas form. This is not enough for a single weapon if further enriched to weapons grade. Some 240 to 250 kilograms of 20 percent-enriched material would be required to produce enough weapons-grade uranium required for a single nuclear weapon. By May 2014, the IAEA reported that as a result of dilution and conversion required by the Joint Plan of Action, Iran had decreased its stock of uranium hexafluoride to 38.4 kilograms.[11]

Iran could reconvert the uranium oxide to uranium hexafluoride, but this process would take several months. Under the current safeguards regime, it is highly unlikely that Tehran could avoid IAEA inspectors detecting the reconversion. Also, material would be lost in the conversion process.

Iran was ostensibly enriching uranium to 20 percent to provide fuel for the Tehran Research Reactor, which produces medical isotopes, and for similar research reactors Iran claims it will build in the future.[12] Although enriching uranium to 20 percent is not necessarily indicative of an intention to make a nuclear weapon, stockpiling uranium at this level is worrisome because if Iran attempted to produce weapons-grade uranium, it could do so much faster using 20 percent-enriched uranium than by starting with 3.5 percent-enriched material. Enriching uranium to 20 percent constitutes about 90 percent of the work needed to enrich uranium to weapons-grade levels.

Moreover, the rationale behind Iran’s production of 20 percent-enriched uranium is dubious, particularly as experts assess that current stockpiles “exceed any realistic assessment of [Iran’s] need.”[13] Tehran does not likely have the technical capacity to build additional research reactors that would use 20 percent-enriched uranium fuel.

One important objective for the P5+1 negotiators will be to cap Iran’s uranium enrichment at 5 percent and limit the size of its enriched uranium stockpile in order to reduce the proliferation risks posed by ongoing production of 20 percent material and large stockpiles of enriched uranium.

The type of centrifuge Iran would use to produce weapons-grade uranium is a key factor in determining how much time it would take for Iran to produce enough weapons-grade material for a nuclear weapon, should it decide to do so. Estimates for the time it would take Iran to bolster the enrichment level of its LEU stockpile from 3.5 percent to weapons-grade range from four to 12 months using the commercial-scale Natanz enrichment plant. The longer time frame, believed to be the assessment of the U.S. government, assumes that Iran would need to reconfigure its centrifuges at Natanz in order to carry out the additional enrichment, while some nongovernmental experts suggest that Iran could close off valves as a shortcut to reconfiguring the plant, leading to a much shorter time frame.[14]

Given the unreliability of the IR-1 machine, some U.S. officials and experts have questioned whether Iran would decide to rely on it to enrich uranium to weapons-grade levels. Robert Einhorn, Department of State special advisor for nonproliferation and arms control issues, told an Arms Control Association gathering in March 2011 that “it would make no sense” for Iran to leave the NPT and produce material for nuclear weapons “with a machine that produces material so inefficiently,” referring to the IR-1.

When the IR-2M centrifuges are operational, the time frame could be reduced even further. These machines are estimated to be three to five times more efficient than the IR-1 centrifuges. Yet, it remains unlikely that Iran could do this without alerting IAEA inspectors, who now have daily access to the Natanz and Fordow sites.

Understanding Breakout Calculations

As the U.S. intelligence community has consistently noted since 2007, Iran has the scientific, technical, and industrial capacity to produce nuclear weapons if it chooses to do so. The U.S. intelligence community has also assessed that if Iran were make a decision to build nuclear weapons, it is more likely that it would seek to do so by means of undeclared, secret facilities, a scenario sometimes called a “sneak-out.” The realistic goal for a final deal in the ongoing negotiations is not to make breakout impossible but to make it a more difficult and unattractive policy option for Iran.

Seeking to identify adequate constraints on Iran’s nuclear program has prompted all manner of intricate calculations of the length of time it would take Iran to get a nuclear weapon. These calculations start with the time required for producing enough fissile material enriched to 90 percent in gaseous form for one bomb, but charting the path to accumulating sufficient fissile material falls short of providing a full understanding of what Iran would require to build nuclear weapons.

Although the production of fissile material is arguably the most resource intensive and difficult step toward building nuclear weapons, there are several additional technical hurdles, including designing and constructing an explosive device and integrating it into a delivery system (most likely a ballistic missile) so it would reliably detonate.

Moreover, these technical criteria constitute an important but incomplete lens through which breakout must be viewed. Real-world timelines must also take into account a broad range of legal and political factors inside and outside Iran. The success or failure of a breakout attempt would depend on the quality and scope of the international inspection regime, the ability of the international community to respond effectively to disrupt the breakout, and the number of weapons Iran would judge to be a credible deterrent.

In most discussions of the subject, it is assumed that Iran would require a minimum of approximately two to three months to produce the fissile material required for one nuclear weapon if it used its existing stockpiles of 3.5 percent-enriched uranium and its 10,200 fully operating IR-1 centrifuges. Two months is a longer period than the timeline estimated prior to last year’s Joint Plan of Action, but far less than the one-year often cited as a goal for any comprehensive agreement.

Former U.S. officials have suggested that the Iranians will need to accept drastic reductions in their inventory of some 20,000 existing centrifuges capable of enriching uranium, for example, to 3,000-4,000 IR-1 operating centrifuges. This would certainly be consistent with the limited “practical needs” of Iran’s nuclear power program for the next several years and push the time it would take to accumulate enough material for one bomb to more than a year.

However, the out-years become more complicated with Iran’s insistence on retaining the right to fuel all future reactors and to develop and install more-efficient centrifuges. Future designs could be even more efficient, dramatically reducing the value of limits on numbers.

Once and if Iran can accumulate a sufficient quantity of uranium hexafluoride for a bomb or several bombs without such an effort being detected and disrupted, it would need to convert the material into powder form, fabricate the metallic core of the weapon from the powder, assemble other weapons components that had been previously developed or acquired on an independent track, and integrate the weapons package into a delivery vehicle.

This process could be more easily hidden, but it would require several months or longer.

David Albright of the Institute for Science and International Security argued in 2012 that Iran had not mastered the technology to weaponize weapons-grade uranium. He concluded that

“[r]egardless of the extent of its past or on-going nuclear weaponization activities…Iran would have to overcome new technological hurdles before it could manufacture a nuclear weapon successfully.”[15]

States developing nuclear weapons typically conduct multiple, large-scale nuclear test explosions to perfect their warhead designs, particularly the smaller, lighter, and more efficient designs needed for missiles.

With existing U.S. national means of intelligence and the International Monitoring System established to verify compliance with the Comprehensive Test Ban Treaty, any Iranian test would very likely be detected. If Iran were to try to “sneak out” to build nuclear weapons, Tehran would have to accept a lower confidence level concerning its warhead design or risk detection.

Iran is very unlikely to break out of the nuclear Nonproliferation Treaty to acquire only one nuclear weapon. Even if Iran were willing to tolerate the large uncertainties deriving from an untested nuclear weapons design, a single weapon would add additional uncertainties regarding missile performance and the ability of the warhead to penetrate the sophisticated missile defenses deployed in the region. Tehran would be staking everything on the perfect performance of one untested system. If it chose to increase the odds of success by planning to build multiple weapons, however, it would increase the need for fissile material, thus lengthening the breakout timelines and increasing the chances of international detection and blocking actions.

Heavy-Water Reactor Project

Another potential path to the construction of nuclear weapons that Iran could pursue is plutonium production using the heavy-water reactor it has been constructing at Arak. This reactor, which Iran claims is intended to produce medical isotopes, is poorly suited for that function but well suited for production of weapons-grade plutonium.

Iran began construction of this reactor, known as the IR-40, in 2004. Construction has been beset by delays, due in part to proliferation-related sanctions, which have prevented Iran from obtaining some of the materials required.

Despite the delays, Iran made noticeable progress on the reactor in 2013 prior to the conclusion of the November 24 Joint Plan of Action. This included installing the upper containment vessel and the reactor vessel and testing prototype uranium fuel assemblies for the reactor in the Tehran Research Reactor. Iran also began producing fuel rods made of natural uranium for the reactor and completed 10 before halting production as part of the November 24 agreement. The reactor will require about 150 fuel rods to operate as intended from the original design.

Prior to the November 24 Joint Plan of Action, it was difficult to determine key reactor design features and a timeline for reactor operations, given Iran’s failure to provide the IAEA with updated design information. Although Iran has provided the agency with that information, in February and March 2014, that information is not public. Yet, if the 40-MWt Arak reactor becomes operational under its original design, experts assess that it could potentially produce about eight kilograms of plutonium per year, enough for about two weapons.[16]

In order to use the plutonium from the reactor, Iran would need a reprocessing facility to separate the plutonium from the reactor’s spent fuel. In 2004, Iran revised its declaration to the IAEA regarding the Arak site and eliminated plans for constructing a reprocessing facility. Iran currently is not known to be working on such a capability, although Tehran admitted to the IAEA in 2003 that it had carried out reprocessing experiments during 1988-1993 without informing the agency.[17]

Ensuring that Iran modifies the design of the reactor to minimize the output of weapons-grade plutonium or converts the facility to a light-water reactor, which is less useful as a source of plutonium, will be important in preventing Iran from producing material for nuclear weapons.

IAEA Safeguards

For nearly 20 years, Iran pursued much of its sensitive nuclear work in secret without informing the IAEA of its activities. It was not until Iran’s facilities at Natanz and Arak were publicly revealed in the fall of 2002 that the agency was able to begin carrying out a thorough accounting of work Iran performed on uranium enrichment and other programs with possible weapons purposes.

Since 2003, many key Iranian facilities have been under IAEA safeguards, with inspections being carried out every few weeks. Most importantly, Iran’s Natanz and Fordow enrichment sites and the conversion plant at Isfahan, which provides the feed material for enrichment, are currently being monitored. Tehran would not be able to move its enriched uranium or uranium hexafluoride feedstock or enrich either material to weapons grade without being discovered. From 2004 until early 2006, Iran voluntarily agreed to implement an additional protocol to its IAEA safeguards agreement.

Yet, prior to the November 2013 interim agreement, Iran kept many activities out of the inspections process. For example, Iran’s centrifuge manufacturing and development work was not safeguarded after 2006, when Iran stopped implementation of its additional protocol. This was preceded by the IAEA finding Iran in noncompliance with its safeguards agreement in September 2005 and the agency’s decision to refer Iran to the UN Security Council in February 2006.

In 2007, Iran stopped sharing early access and design information for its nuclear facilities with the IAEA, as it is obligated to do under the so-called modified Code 3.1 of its safeguards agreement. Although Iran announced it would revert to the original arrangement, the agency said the modified arrangement cannot be unilaterally altered and that Iran was still required to provide the notifications required by Code 3.1.[18]

International Atomic Energy Agency Verification Measures

Safeguards Agreement

Safeguards are activities that the International Atomic Energy Agency (IAEA) undertakes to verify that a state is living up to its international commitments not to use nuclear programs for nuclear-weapons purposes. State parties to the nuclear Non-Proliferation Treaty are obligated to have a safeguards agreement in place. Safeguard activities undertaken by the agency are based on a state’s declaration of its nuclear materials and nuclear-related activities. Verification measures include on-site inspections, monitoring and evaluation.

Status of Iran’s Safeguards Agreement: Iran’s safeguards agreement entered into force in 1974. It grants the IAEA access to nuclear sites, including Iran’s uranium enrichment sites at Natanz and Fordow, the fuel fabrication plant at Esfahan, the Arak heavy water reactor, and the Tehran Research Reactor, for monitoring and verification purposes.

Modified Code 3.1 of the Subsidiary Arrangements to a Safeguards Agreement

Modified Code 3.1 requires countries to submit design information for new nuclear facilities to the IAEA as soon as the decision is made to construct, or authorize construction, of the facility.

Status of Iran’s Code 3.1 Agreement: In 2003, Iran accepted modified Code 3.1 but reneged unilaterally in March 2007. The IAEA maintains that subsidiary arrangements, including 3.1, cannot be altered unilaterally. There also is no mechanism in the safeguards agreement to suspend implementation of Code 3.1. Therefore, the IAEA maintains that it remains in force, and Iran is not following through with its obligations under Code 3.1 to provide the agency with updated design information for new and existing nuclear facilities.

Implications of Implementing Code 3.1 in Iran: If Iran implements Code 3.1, the IAEA will receive information about any plans Tehran has to expand its nuclear program earlier than it would under the existing safeguards agreement. Iran would also be obligated to share any design changes to existing nuclear facilities. This would be particularly useful in the case of the Arak heavy water reactor because Iran has not responded to the IAEA’s request to provide updated design information.

Additional Protocol

The Additional Protocol is a legal document granting the IAEA inspection authority beyond what is permitted by a safeguards agreement. Additional Protocols are voluntary agreements negotiated on a state-by-state basis with the IAEA. A principal aim is to enable the IAEA inspectorate to provide assurance that there are no undeclared activities and all declared nuclear activities are for peaceful purposes. Under the Additional Protocol, the IAEA is granted expanded rights of access to information and sites. States must provide information about, and IAEA inspector access to, all parts of a State’s nuclear fuel cycle - including uranium mines, fuel fabrication and enrichment plants, and nuclear waste sites - as well as to any other location with nuclear material. Additional Protocols typically include provisions granting multiple entry visas to inspectors, access to research and development activities, information on the manufacture and export of sensitive nuclear related technologies and allow for environmental samples.

Status of Iran’s Additional Protocol: Iran negotiated an Additional Protocol with the IAEA and signed the agreement in 2003. Between 2003 and 2006 Iran voluntarily implemented the Additional Protocol, but never ratified the document. In 2006, Iran announced that it would no longer implement the provisions of the agreement.

Implications of Implementing the Additional Protocol in Iran: With the Additional Protocol in place, the IAEA will be able to visit all of the facilities associated with Iran’s nuclear activities, including sites that it does not currently have access to, such as the uranium mines, Iran’s centrifuge production facilities, and its heavy water production plant. The Additional Protocol also substantially expands the IAEA’s ability to check for clandestine, undeclared, nuclear facilities by providing the agency with authority to visit any facility, declared or not, to investigate questions about or inconsistencies in a state’s nuclear declarations.

The IAEA will also be able to visit any site on very short notice. These monitoring and verification measures will give the agency a more complete picture of Iran’s nuclear activities and allow for early detection of deviations from peaceful activities. Early notification would give the international community time to respond to any dash Iran might make toward nuclear weapons.

As a result, the agency did not have regular access to the heavy-water reactor under construction at Arak, and Iran refused to share plans regarding the construction of any additional nuclear facilities. Tehran also refused IAEA requests to install real-time camera monitoring at its enrichment facilities, a measure that would provide the earliest indication of any Iranian move to begin producing weapons-grade material.

Until 2013, Iranian officials argued that their actions were justified because the IAEA and the UN Security Council were trying to deprive Iran of the inherent rights to which all NPT members are entitled. In fact, Iran is reneging on the terms of the safeguards agreement it concluded with the IAEA, one of its core NPT responsibilities on which its rights to nuclear technology is conditioned. The agency is fulfilling its responsibility by exercising due diligence in monitoring Iran’s program so that it can determine whether the program encompasses weapons-related activities.

Warhead Development Program

Although much of Iran’s nuclear program consists of dual-use technology that can be dedicated to civil nuclear energy and nuclear weapons use, Tehran is widely believed to have been engaged in a series of activities that can result in development of a nuclear warhead. U.S. intelligence estimates have long referred to these activities as evidence of an Iranian nuclear weapons program.

In November 2011, the IAEA released information in an annex to its quarterly report that detailed Iran’s suspected warhead work based on intelligence it received from the United States and several other countries, as well as its own investigation.[19] According to the report, Iran was engaged in an effort prior to the end of 2003 that spanned the full range of nuclear weapons development, from acquiring the raw nuclear material to working on a weapon that could eventually be delivered via a missile.

This judgment is consistent with the 2007 NIE on Iran, which assessed “with high confidence that until fall 2003, Iranian military entities were working under government direction to develop nuclear weapons” and that the program was halted in the fall of 2003. It assessed “with moderate confidence that Tehran had not restarted its nuclear weapons program.”

According to the November 2011 IAEA report, however, some information from IAEA member states suggests that some activities that would be “highly” relevant to a nuclear weapons program have resumed since 2004. Subsequent IAEA reports indicate that the agency received further information about periodic activities related to weapons development.

The series of projects that made up what the IAEA in its November 2011 report called “the AMAD Plan,” appears to have been overseen by senior Iranian figures who were engaged in working-level correspondence consistent with a coordinated program.[20] Among the key components of this program were the following:

  • Fissile material production. As documented in previous IAEA reports, Iran maintained an undeclared effort to produce uranium tetrafluoride, also known as Green Salt and a precursor for the uranium used in the enrichment process. The affiliation between this project and other projects directly related to warhead development suggests that Iran’s nuclear weapons program included fissile material production and warhead development. Although the report does not detail a uranium-enrichment effort as part of the AMAD Plan, the secret nature of the Natanz enrichment plant prior to 2002 suggests that it was originally intended to produce HEU for weapons.

  • High-explosives testing. Iran’s experiments involving exploding bridge wire detonators and the simultaneous firing of explosives around a hemispherical shape point to work on nuclear warhead design. The agency says that this type of high-explosives testing matches an existing nuclear weapons design based on information provided by nuclear-weapon states. Iran admits to carrying out such work, but claims it was for conventional military and civilian purposes and disputes some of the technical details.
  • Warhead design verification. Iran carried out experiments using high explosives to test the validity of its warhead design and engaged in preparatory work to carry out a full-scale underground nuclear test explosion.
  • Shahab-3 re-entry vehicle. Documentation reviewed by the IAEA has suggested that as late as 2003, Iran sought to adapt the payload section of a Shahab-3 missile for accommodating a nuclear warhead. Confronted with some of the studies, Iran admitted to the IAEA that such work would constitute nuclear weapons development, but Tehran denies carrying out the research.

Iran has denied pursuing a warhead-development program and claims that the information on which the IAEA assessment is based is a fabrication. Until this year, Tehran has not cooperated with IAEA efforts over the past several years to verify Iran’s claims comprehensively, adding to suspicions about the role of Iran’s nuclear intentions. Iran has provided some information in the past related to specific claims, but any optimal resolution to the Iran nuclear issue would need to include a full accounting of Iran’s past activities and assurances that any warhead-related activities that occurred or are still occurring have been halted.

In February 2012, Iran and the IAEA began negotiating a framework agreement to resolve the agency’s outstanding concerns about Iran’s possible weapons-related activities. In a document outlying an approach for addressing the unresolved issues, the IAEA grouped its concerns into three areas. Two concerned the clarity and completeness of Iran’s initial declaration to the IAEA, and the third addressed the activities that could be related to the possible military dimensions of Iran’s nuclear program.

Iranian and IAEA officials met 10 times between February 2012 and June 2013, but failed to reach an agreement on the scope and sequence of the agency’s investigation.

These meetings resumed after Rouhani’s inauguration as president of Iran in August 2013. On November 11, 2013, Iran and the IAEA concluded a framework agreement for moving forward to resolve the outstanding concerns. Under the terms of the framework, Iran and the IAEA agreed to resolve all outstanding issues in a step-by-step manner. The first set of actions included six steps for Iran to take within the first three months. At the conclusion of the three months, Iran and the IAEA met again, in February, and agreed on the next set of actions, which Iran was to complete by May 15. This set of seven actions included the first issue concerning the possible military dimensions of Iran’s nuclear program. Iran provided the IAEA with information on exploding bridge wire detonators ahead of the May 15 deadline and is working with the IAEA on follow-up questions stemming from its original report.

On May 21, 2014, Iran and the IAEA announced a set of five more actions, to be completed by August 25. These actions included an additional two issues concerning the possible military dimensions of Iran’s nuclear program: initiation of high explosives and modeling and calculations related to neutron transport and their alleged application to compressed materials. Both of these activities relate to development of a nuclear weapon.

Iran-IAEA Framework for Cooperation

Under the Joint Statement on a Framework for Cooperation, signed November 11, 2013, Iran and the International Atomic Energy Agency (IAEA) committed to resolve the agency’s concerns through a step-by-step process to address all outstanding issues. An annex to the framework laid out the first six actions that Iran pledged to take within three months. On February 9, 2014, Iran and the IAEA announced an additional seven actions that Iran would take by May 15, 2014. A May 20, 2014, meeting resulted in an agreement on an additional five actions to be taken by August 25, 2014.

Iranian actions to be completed by February 11, 2014

  • Provide mutually agreed relevant information and managed access to the Gchine mine in Bandar Abbas.
  • Provide mutually agreed relevant information and managed access to the Heavy Water Production Plant.
  • Provide information on all new research reactors.
  • Provide information with regard to the identification of 16 sites designated for the construction of nuclear power plants.
  • Provide clarification of the announcement made by Iran regarding additional enrichment facilities.
  • Provide further clarification of the announcement made by Iran with respect to laser enrichment technology.

Iranian actions to be completed by May 15, 2014

  • Provide mutually agreed relevant information and managed access to the Saghand mine in Yazd.
  • Provide mutually agreed relevant information and managed access to the Ardakan concentration plant.
  • Submit an updated Design Information Questionnaire for the IR-40 reactor (heavy-water reactor at Arak).
  • Take steps to agree with the IAEA on the conclusion of a Safeguards Approach for the IR-40 reactor.
  • Provide mutually agreed relevant information and arrange for a technical visit to Lashkar Ab’ad Laser Centre.
  • Provide information on source material that has not reached the composition and purity suitable for fuel fabrication or for being isotopically enriched, including imports of such material and on Iran’s extraction of uranium from phosphates.
  • Provide information and explanations for the IAEA to assess Iran’s stated need or application for the development of exploding bridge wire detonators.

Iranian actions to be completed by August 25, 2014

  • Exchange information with the IAEA with respect to the allegations related to the initiation of high explosives, including the conduct of large-scale high-explosives experimentation in Iran.
  • Provide mutually agreed relevant information and explanations related to studies made and papers published in Iran in relation to neutron transport and associated modeling and calculations and their alleged application to compressed materials.
  • Provide mutually agreed information and arrange a technical visit to a centrifuge research and development center.
  • Provide mutually agreed information and managed access to centrifuge assembly workshops, centrifuge rotor production workshops, and storage facilities.
  • Conclude the safeguards approach for the IR-40 reactor.

Iran’s Nuclear Weapons Options

If Iran decided to try to build nuclear weapons, it could choose among three basic paths.

  1. Enrich safeguarded LEU to weapons-grade uranium at existing facilities (shortest time frame).
  2. Use a parallel, clandestine nuclear program with a full series of nuclear facilities built in secret (longest time frame).
  3. Divert safeguarded material to a secret facility and enrich to weapons grade (moderate time frame).

Most estimates of the time necessary for Iran to produce a nuclear weapon are based on the use of the Natanz enrichment plant to produce HEU. Assessments range from about two months to one year using IR-1 centrifuges. This discrepancy is based on a number of factors, including the need for Iran to reconfigure the facility for higher-level enrichment and the efficiency of its centrifuges.

Such an approach would carry serious risks for Tehran because its facilities and nuclear material are under IAEA safeguards and any move in the near future to begin enrichment to weapons grade would be discovered almost immediately after the process began.

Efforts by Iran to enrich uranium to weapons grade at Natanz might even provoke an attack on Natanz and Fordow and possibly other nuclear sites by the United States or Israel to disrupt the process. It is highly unlikely that Iran would decide to take such a step unless it could significantly reduce the time frame to produce weapons-grade uranium and avoid detection and disruption. Efforts to reduce that time frame include operating thousands of advanced centrifuges and stockpiling a sufficient amount of reactor-grade enriched uranium needed to produce fissile material for several weapons. Continuous monitoring and a freeze on centrifuge installation under the November 24 agreement make this route even less likely.

The Fordow facility also could be used to carry out enrichment to weapons grade. Because Fordow only has a capacity of about 3,000 centrifuges, however, Iran’s options for a rapid breakout at Fordow are more limited. Iran would need to install advanced centrifuges to enrich to weapons grade quickly. As with the Natanz plant, if the time frame for enrichment was too long, Iran would risk the facility being destroyed or at least rendered inoperable before it could complete the process.

Because of these vulnerabilities, if Iran was to try to enrich uranium to weapons grade, it might seek to use covert facilities in some form. The 2007 NIE assessed with moderate confidence that “Iran would probably use covert facilities—rather than its declared nuclear sites—for the production” of HEU for a weapon.

A clandestine, parallel nuclear program would require that Iran construct a series of additional nuclear facilities along the uranium-enrichment path that mirrors its existing facilities. Because Iran’s declared nuclear material is monitored under IAEA safeguards, Iran would need an entirely separate stream of material, beginning with uranium ore. Iran would need parallel facilities for the entire process required to build a bomb, all the way to weaponizing the enriched uranium.

Iran’s uranium-mining and -milling operations to produce yellowcake do not currently fall under safeguards, although such activities could be detected through intelligence means. Also, Iran would need to construct another conversion plant to produce uranium hexafluoride, secretly manufacture large numbers of centrifuges, build an enrichment plant or plants to produce weapons-grade uranium, and construct a fabrication plant to manufacture the material into metal cores. Producing weapons-grade uranium using such a covert series of facilities appears to have been Iran’s original intent prior to the exposure of its nuclear facilities in 2002.

Using such a path, Iran could potentially develop nuclear weapons without the international community’s knowledge as long as all duplicate facilities, related manufacturing processes, and nuclear material remained hidden. In the past, Iran’s two major enrichment facilities have been detected by foreign intelligence well before they became operational.

A clandestine program would require more time and far more resources for investment in duplicate facilities. Iran is already believed to be resource strained by sanctions, and an extended period of time would increase the risk that clandestine facilities would be uncovered. With more-intensive international inspections expected to be part of a comprehensive nuclear agreement between the P5+1 and Iran, it is unlikely that Iran would be able to pursue this path.

Iran could develop nuclear weapons through diversion to covert sites, which is an amalgam of the first two approaches. This approach might entail the construction of a secret uranium-enrichment plant where Iran would further enrich its stockpile of 3.5 percent-enriched uranium to HEU. Tehran would likely need to construct another facility where that HEU would be fashioned into metallic cores for use in weapons to avoid using its declared fuel-manufacturing plant at Esfahan. Such an approach would avoid the need to completely duplicate many aspects of Iran’s nuclear program while carrying out the final stages of weapons development in locations Tehran believed to be safe from pre-emptive attack. This path is less likely, however, with the increased monitoring put in place under the November 2013 Joint Plan of Action. Nevertheless, absent a comprehensive deal or continued increased monitoring, this remains a concern.

Iran announced in 2009 that it planned to build 10 additional uranium-enrichment plants, which is a goal likely beyond Iran’s resources, but a decision to build any additional plants without revealing their location suggested that Iran wanted to maintain locations where it could enrich in secret. In 2011, Iranian officials said that plans to construct any additional plants would be postponed for a couple of years. As part of its November 11, 2013, agreement with the IAEA, Iran has provided the agency with information about its plans for future enrichment sites, but these details are not public. Construction cannot begin during the implementation period of the Joint Plan of Action due to provisions in the text that prohibit moving forward on further enrichment facilities. U.S. officials have reportedly expressed confidence that there is no secret uranium-enrichment site at present and attempts to build additional covert facilities would likely be detected.[21]

Under the provisions of the interim agreement, any breakout scenario becomes less likely. With a reduced stockpile of 20 percent-enriched uranium, Iran would need more time to produce significant quantities of fissile material. Moreover, the Natanz and Fordow sites are inspected on a daily basis, and the IAEA has access to Iran’s centrifuge production plant and storage facilities. Major construction on the Arak heavy-water reactor has been halted. Any attempt to break out using known enrichment facilities would be detected within days, and the increased information about Iran’s centrifuge production and supplies makes it more likely that the agency would detect any diversion to covert facilities.

Iran’s Nuclear Delivery Path

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Iran has a determined ballistic missile development program and would likely make such missiles its delivery vehicle of choice if it decided to build nuclear weapons. Indeed, Iran is suspected to have carried out R&D on mounting a nuclear warhead on a missile and detonating it at an appropriate height.[22] Ballistic missiles offer a preferred delivery path compared to Iran’s aging air force, which remains predominately based on 1970s-era, U.S.-supplied aircraft and would be very vulnerable to the air defenses of target states.

Although Iran is believed to have the largest and most diverse missile arsenal in the region, official U.S. assessments say that Iran’s ballistic missile program has been focused on increasing the sophistication of its short- and medium-range ballistic missiles.[23] With a range of up to 3,000 kilometers, missiles in these categories are capable of striking targets as far as Israel and Turkey.

Iran’s currently operational medium-range ballistic missile systems are derived from 1950s-era Soviet Scud short-range ballistic missile technology, which Iran received from North Korea. The liquid-fueled Shahab-3, Iran’s principal medium-range ballistic missile, is essentially identical to the North Korean Nodong missile. The most capable ballistic missile in Iran’s confirmed operational inventory is the Ghadr-1, which is an enhanced version of the Shahab-3 and is able to carry a 750-kilogram warhead at least 1,600 kilometers and possibly up to 2,000 kilometers.

Iran claims to have deployed the two-stage, solid-fueled Sejjil-2 medium-range ballistic missile, with a range of 2,000 kilometers, but the United States has not confirmed that this system is operational.

A key aspect of Iranian efforts to increase the sophistication of its missile program is the development of solid-fuel missile technology. Solid-fueled missiles hold some advantages over Tehran’s predominately liquid-fueled missile arsenal, including shorter launch times, greater mobility, and easier handling and storage.

If Iran developed a nuclear warhead for threatening Israel, the Sejjil-2 missile would be the most likely delivery platform. Its range would permit it to be fired at Israel from any part of Iran. A September 2013 military parade in Tehran included 12 Sejjil-2 missiles. The system was first flight-tested successfully in May 2009 and last tested in February 2011.

In addition to enhancing its medium-range ballistic missile capabilities, Iran has been gradually improving its technical capacity to develop and produce longer-range ballistic missiles. Iran’s satellite launch program and its successful use of space-launch vehicles is central to this effort. The ability to put a satellite in space does not guarantee an ability to accurately target and deliver a warhead at long ranges, but there is sufficient overlap in propulsion, staging, and other important component technologies used by space-launch vehicles to make them a useful test bed for developing long-range missile systems. Nonetheless, Iran appears to have a genuine interest in developing space-launch capabilities beyond their military applications.

Iran placed a satellite in orbit on several occasions, in February 2009, June 2010, June 2011, and February 2012. All four launches used a two-stage Safir space-launch vehicle, and in the February 2012 launch, a modified Shahab-3 ballistic missile was identified by experts as the first stage. The Safir itself is not suitable as a military system because of its limited carrying capacity, and Iran is unlikely to convert it into a military missile. Iran showed a mockup of a larger space-launch vehicle called the Simorgh in 2010, but it has yet to launch this new system.

Because Iran has not flight-tested a long-range military system or a space-launch vehicle capable of being converted to such a system, an intercontinental ballistic missile capable of targeting the United States is unlikely to be available before 2020.

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