This is a history of Iran's effort to acquire technology that could be used to build a nuclear weapon. The emphasis is on Iran's technical achievements rather than its motives, and the essay relies primarily on reports produced by the International Atomic Energy Agency (IAEA).
International interest in Iran was heightened dramatically in the summer of 2002, when the existence of two nuclear sites was revealed by an exiled Iranian resistance group. Within a year, the world realized that Iran had built or was building everything needed to produce enriched uranium, which could fuel nuclear weapons as well as nuclear reactors. The sites included a uranium mine at Saghand, a yellow cake production plant near Ardakan, a pilot uranium enrichment plant at Natanz, and a commercial-scale enrichment facility on the same site. In addition, Iran was continuing work on a 1,000 megawatt nuclear reactor at Bushehr and was building a heavy water production plant at Arak, next to which Iran planned to build a 40 megawatt heavy water reactor. Beginning in March 2003, following revelations that Iran had concealed nuclear work from the IAEA, the Agency has been investigating Iran's nuclear history.
Iran has long argued that its nuclear program is benign, legal and authorized by its membership as a non-nuclear weapon state in the nuclear Non-Proliferation Treaty (NPT), which guarantees its members the right "to develop…nuclear energy for peaceful purposes." However, the United States believes that Iran has no need for nuclear energy and that its civilian energy program serves only to camouflage a nuclear weapon effort. In light of Iran's oil and gas reserves, the United States assesses that it would cost Iran much more to produce a kilowatt of electricity from uranium than from petroleum. In June 2003, U.S. President George W. Bush staked out the U.S. position by saying that the United States and its allies "will not tolerate the construction of a nuclear weapon" in Iran.
EARLY NUCLEAR EFFORTS
Under the Shah, Iran launched a series of ambitious nuclear projects that relied on assistance from the United States and Europe. According to Akbar Etemad, the President of the Atomic Energy Organization of Iran (AEOI) from 1974 through 1978, Iran was already carrying out nuclear research and education at the University of Tehran when the NPT entered into force on March 5, 1970. The work centered on a five megawatt research reactor supplied by the United States, which began operation in 1967.
By the mid-1970s, according to Etemad, Iran had launched an extensive nuclear energy program. In 1974, the Shah set the goal of producing roughly 23,000 megawatts of electrical power from a series of nuclear power stations within twenty years. A host of contracts between Iran and nuclear suppliers in Europe and the United States followed: Iran struck a deal with Kraftwerk Union (KWU, a Siemens subsidiary) of then-West Germany to build two 1,200 megawatt reactors at Bushehr and negotiated with the French company Framatome for two additional 900 megawatt reactors. In 1974, Iran reportedly invested $1 billion in a French uranium enrichment plant owned by Eurodif, a European consortium. Etemad also described Iran's indigenous work on the nuclear fuel cycle in the 1970s, including plans for a new nuclear research center at Isfahan and the exploration of uranium mining and ore processing.
The 1979 Iranian revolution halted this work for a number of years. The war
with Iraq, which began in 1980, consumed resources and damaged Iran's
existing nuclear infrastructure. The two power reactors under construction
at Bushehr were bombed several times, after which Siemens abandoned the project.
During Akbar Hashemi Rafsanjani's presidency, beginning in the late 1980s, Iran's nuclear program revived. By the early 1990s, as Iran recovered from the war with Iraq, its nuclear program was once again moving forward, based on assistance from Russia, China and Pakistan. With China, Iran signed two nuclear cooperation protocols, in 1985 and again in 1990. And in 1995, Iran concluded a protocol of cooperation with Russia to complete the construction of the reactor at Bushehr and possibly supply a uranium enrichment plant. Some of the items originally contemplated in these deals, like the enrichment plant, were never delivered due to pressure from the United States. Others, like Bushehr, served as a screen behind which Iran obtained sensitive equipment that would not be sold on its own because of its bomb-making potential. Throughout the 1990s, entities in Russia and China continued to help Iran, despite occasional pledges from their governments to curtail nuclear assistance. During this period, Iran is also believed to have received uranium enrichment technology through the black market network run by Pakistani scientist A. Q. Khan.
The deals—official and illicit—struck by Iran in the 1990s allowed it to make important progress in its indigenous nuclear effort. By 2003, when the scope of its nuclear program became clear, Iran had already mastered the technology needed to make enriched uranium, one of the materials that can be used to fuel a nuclear weapon. Because many of its nuclear experiments were conducted in violation of its inspection agreement with the IAEA, Iran was forced to provide new information on this work and to explain its purpose. Iran's explanations, along with the results of the IAEA's inspections, were published in a series of Agency reports beginning in June 2003.
SEEKING NUCLEAR FUEL
Iran's pursuit of nuclear expertise has taken it down both of the paths to nuclear weapon fuel, which consists of either enriched uranium or plutonium. These materials are "fissile" because they are unstable and fission, or split, when struck by neutrons. Both can fuel a nuclear bomb or be used as fuel in a nuclear power reactor. However, producing nuclear fuel, regardless of its ultimate use, is a difficult task.
The Uranium Path
The difficulty in producing a significant amount of uranium 235—the fissile form of uranium needed to fuel a nuclear weapon—is that natural uranium contains only a small amount (.7%) of this isotope. Generating a substantial amount of U-235 requires a series of steps that begins at the mine and ends with the production of enriched uranium fuel. Iran has sought to master each step in this process.
Mining and milling
Before uranium can be refined to fuel a reactor or a bomb, it must be mined. This is the first step in what is referred to as the "front end" of the nuclear fuel cycle. On February 9th, 2003, Iranian President Mohammad Khatami declared that his government intended to extract uranium from a mine at Saghand, in the province of Yazd. The mine is a key part of Iran's plan to produce nuclear fuel indigenously. According to Dr. Ghannadi-Maragh, the Vice President of Iran's Atomic Energy Organization, the mine site consists of two deposits, with a combined reserve of 1,550,000 tons of uranium ore and an average grade of 553 parts per million.
Once mined, uranium ore must be processed into a uranium concentrate called yellowcake. In February 2003, Iranian authorities admitted to producing yellowcake at a milling plant near the city of Yazd. The AEOI had approved the construction of a yellowcake production plant in 1994 and contracted with an Iranian company to build the plant in 1999. The plant is expected to yield about 50 tons of yellowcake per year.
China is believed to have been the source of the Saghand mining technology. Iran has admitted that Chinese experts participated in detailed exploration work for the mine. Experts from China's Beijing Research Institute of Uranium Geology have conducted scientific exchanges with Iranian nuclear scientists and have explored in Iran in the past. In addition, the National Council of Resistance in Iran (NCRI), an exiled Iranian opposition group, claims to have seen Chinese experts at the Saghand site.
Once mined and concentrated into yellowcake, the uranium must be converted to a gas. This gaseous form of uranium, called uranium hexafluoride (UF6), serves as the feedstock for centrifuges, which then enrich uranium to a form suitable for either reactor fuel or nuclear weapons. In 2000, the Iranian government informed the IAEA that a plant for uranium conversion was being constructed at Esfahan (Isfahan). In a speech to the IAEA in May 2003, Gholamreza Aghazadeh, head of the AEOI, said that the conversion facility, which is located at the Esfahan (Isfahan) Nuclear Technology Center (ENTC), would be used to convert yellowcake into UF6.
According to Iran, the conversion plant is intended to have a number of process lines for transforming uranium compounds; production of uranium dioxide (UO2) and uranium metal, along with UF6, are planned. The planned process lines include: uranium ore concentrate into UF6 (yielding 200 t annually of UF6 ); low enriched UF6 into UO2 (yielding 30 t annually of UO2 enriched to 5% U-235); depleted UF6 into uranium tetrafluoride (UF4) (yielding 170 t annually of depleted UF4); low enriched UF6 into low enriched uranium metal (yielding 30 kg annually of uranium metal enriched to 19.7% U-235); and depleted UF4 into depleted uranium metal (yielding 50 t annually of depleted uranium metal).
China is widely acknowledged to be the source of information for the conversion plant. As part of a 1997 agreement with the United States to prevent new cooperation and to halt all existing projects with Iran in the nuclear field, China pledged to cancel a project to help Iran build a conversion plant. Despite this promise, however, China appears to have provided Iran with a blueprint for the plant. Iran admits that the conversion plant is based on a design provided by a foreign supplier in the mid-1990s. China is also believed to have given Iran design information and test reports for equipment.
In addition, China supplied uranium compounds in 1991, which Iran did not declare to the IAEA and which allowed Iran to conduct laboratory tests of the processes that will be used in the conversion plant. These compounds included 1.9 kg of UF6, 402 kg of UF4 and about 400 kg of natural UO2.
After uranium is mined and converted into a gaseous form, the U-235 isotope must be separated from the more abundant U-238 isotope in a process called enrichment. But because these two uranium isotopes are identical chemically, they cannot be readily separated by a simple chemical reaction. They must be parted by exploiting the slight difference in their weights. Uranium enriched to between three and five percent U-235 is typically used to fuel power reactors of the type Iran is constructing at Bushehr; uranium enriched to over 90% U-235 can be used to fuel nuclear weapons.
There are a number of different ways to enrich uranium. Iran has focused on two: gas centrifuge and laser isotopic separation.
Centrifuge separation works by passing UF6 through high-speed rotational machines called centrifuges. The different weights of the uranium isotopes cause them to separate, with the heavier U-238 being thrown to the outside of the centrifuge and the lighter U-235 staying nearer the inside. Centrifuges require several repetitions with the enriched product to reach the desired level of concentration; more repetitions are required to obtain a higher concentration of U-235, which is necessary to produce weapon-grade fuel.
Iran's centrifuge program was launched in 1985 at facilities controlled by the AEOI in Tehran. Around 1987, Iran received a centrifuge design through what the IAEA has termed a "foreign intermediary." During this first phase of Iran's centrifuge effort, Iran also obtained about 2,000 components from abroad. According to a February 2004 Malaysian police report, Iran received two containers of centrifuge parts, worth $3 million, through the Khan network. This transfer allegedly took place between 1994 and 1995.
In 1997, Iran moved its centrifuge development effort to the Kalaye Electric Company in Tehran. According to Iranian authorities, from 1997 through 2002, Kalaye was used to test and assemble centrifuges for uranium enrichment. In October 2003, after initial denials, Iran admitted that it had used 1.9 kg of UF6, allegedly imported from China in 1991, to test centrifuges at Kalaye. This work took place between 1998 and 2002 and, according to Iranian officials, achieved an enrichment level of 1.2% U-235. The IAEA first visited parts of Kalaye in March 2003 and Agency inspectors were allowed to take environmental samples at the site during a follow-up visit in August 2003. During this visit, inspectors noted that "considerable modification" had been made to the facility since their visit in March.
Beginning in 2002, Iran's centrifuge enrichment program was moved to Natanz, the location chosen for a 1,000 centrifuge pilot plant and a commercial-scale facility expected to house over 50,000 centrifuges. According to Iran, the Natanz site will produce nuclear fuel for power plants using uranium enriched from three to five percent U-235.
The Natanz site was revealed publicly in August 2002 by the NCRI and first visited by the IAEA in February 2003. In his report to the IAEA Board of Governors in March 2003, IAEA Director General Mohamed ElBaradei stated that the site included a pilot plant that was "nearly ready for operation, and a much larger enrichment facility still under construction."
Iran first used UF6 to test a centrifuge at the pilot plant in June 2003, and in August 2003 tested a ten-machine cascade using UF6. Enrichment work at the pilot plant was suspended beginning in November 2003, following an agreement between Iran and Britain, France and Germany. However, Iran continued to manufacture centrifuge parts and assemble centrifuges at a number of workshops.
The machines at Natanz are of an early European design, similar to the P-1 centrifuge that has been under the control of the Khan Research Laboratories (KRL) in Pakistan, and which was stolen from Western Europe's Urenco program during the1970s and 1980s. According to a paper presented by France at a Nuclear Suppliers Group meeting in May 2003, Iran is believed to have improved on the Pakistani design and now has "a model effective enough to consider enrichment on an industrial scale."
In addition to the P-1 centrifuge, Iran has a program to develop the more advanced P-2 model. The P-2 uses a maraging steel rotor with bellows and is similar to another early European centrifuge design. Iran received a design for the P-2 in 1994 from what the IAEA termed "foreign sources." The IAEA has concluded that Iran received the same drawings for the P-2 as Libya, which received the design, along with P-2 components, through the Khan network. According to Iran, mechanical testing of the P-2 rotors began in 2002, using carbon composite rotors manufactured domestically rather than rotors made with maraging steel, which Iran was unable to produce. The AEOI contracted with a private company based in Tehran to produce the rotors and to conduct the tests, allegedly without using nuclear material. Iran has procured magnets useful in the P-2 from Asian suppliers and has sought to acquire about 4,000 magnets suitable for the P-2 through a European intermediary.
- Laser Isotopic Separation
Because isotopes of different masses absorb different wavelengths of light, uranium isotopes can be separated by lasers precisely tuned to excite or ionize only the U-235. The U-235 is then separated out using a chemical reaction or magnetic forces that attract the excited atoms and leave behind the neutral ones. Iran has pursued two types of laser enrichment technology: the first, atomic vapor laser isotope separation (AVLIS), has achieved the greatest success; the second, molecular laser isotope separation (MLIS), appears not to have progressed as far.
Iran's laser enrichment program began before the 1979 revolution and relied on assistance from at least four foreign sources. In 1975, Iran contracted with a foreign supplier for a laboratory to study uranium metal. The laboratory, which was established at the Tehran Nuclear Research Center (TNRC), contained two mass spectrometers. In the late 1970s, Iran contracted with a second supplier for help with the study of MLIS technology.
Then, in 1991, Iran ordered a Laser Spectroscopy Laboratory (LSL) and a Comprehensive Separation Laboratory (CSL) from a third supplier. Iran received 50 kg of natural uranium metal from the same supplier in 1993. Both laboratories were originally set up at the TNRC, where, between 1999 and 2000, eight kilograms of uranium metal were used in AVLIS enrichment experiments. The labs were then relocated to Lashkar Ab'ad in October 2002, where further AVLIS enrichment experiments were carried out using 22 kg of the uranium metal. Iran had previously established a pilot plant for laser enrichment at Lashkar Ab'ad. According to Iranian laboratory reports supplied to the IAEA, the average level of enrichment in these experiments was between eight and nine percent, and occasionally as high as 15%. This is above the level of three percent Iran had originally claimed. The IAEA has estimated that Iran's AVLIS installation at Lashkar Ab'ad had the capacity to produce one gram of uranium per hour, but could not operate continuously.
Iran contracted with a fourth supplier in the late 1990s for information and equipment related to laser enrichment but secured only some of the equipment it had requested, which was delivered to Lashkar Ab'ad. This equipment was suitable for use in AVLIS experiments.
After conducting this laboratory-scale work, and before informing the IAEA
of it, Iran dismantled the relevant equipment and moved it to a storage facility
The Plutonium Path
Iran has also sought the ability to produce plutonium, a second fissile material that can be used to fuel nuclear weapons. But because plutonium exists naturally only in trace amounts, it must be manufactured in a nuclear reactor. This is done by bombarding U-238 reactor fuel with slow neutrons. When the U-238 captures a neutron, the U-239 isotope is produced, which decays into plutonium 239.
Tehran Research Reactor (TRR)
In the late 1960s, the United States supplied the TNRC with a five megawatt research reactor, hot cells and 93% enriched uranium reactor fuel. The United States stopped the fuel supply after the revolution. In the late 1980s, Argentina reportedly helped Iran reconfigure the reactor's core and later provided about 115 kg of uranium enriched to 20% U-235. This fuel was delivered in 1992.
In October 2003, Iran acknowledged that between 1988 and 1992 it had irradiated depleted uranium dioxide targets (UO2) in the reactor and then conducted plutonium separation experiments in hot cells in a nearby building. According to Iran, seven kilograms of UO2 were irradiated, three kilograms of which were processed into separated plutonium. The separated plutonium was presented to inspectors from the IAEA in November 2003 at the Jabr Ibn Hayan Laboratories, located at the TNRC. Iran estimated that it had produced 200 micrograms. However, the inspectors concluded that Iran understated the amount of plutonium and that the age of the plutonium was less than the 12-16 years Iran declared.
Light-water reactor at Bushehr
Russia is supplying Iran a 1,000 megawatt pressurized light-water reactor, which is under construction at the Iranian port of Bushehr. Russia took over the project in 1995, after West Germany halted its construction of the plant following the revolution. The plant is capable of contributing about four percent of Iran's total electricity output to the national power grid. The facility is also capable of providing Iran with enough weapon-grade plutonium to construct approximately 35 nuclear weapons annually. This assessment is based on an estimate of the plutonium output from a typical 1,000 megawatt pressurized light-water power reactor.
To use the plutonium from Bushehr in a nuclear weapon, however, Iran would have to construct a plant to extract plutonium from the spent reactor fuel. Iran would also have to keep the spent fuel. Russia appears to have an agreement with Iran to provide low-enriched uranium fuel through the first decade of the Bushehr plant's operation, and Russia has made delivery of the first core-load of fuel contingent on Iran's agreement to return the spent fuel to Russia. In a June 2003 interview, Russian Atomic Energy Minister Alexander Rumyantsev stated that Russia will not provide any fresh fuel to Iran until such an agreement is signed.
Nevertheless, Iran has made a number of purchasing attempts that indicate it seeks a capacity to reprocess and manipulate spent fuel. According to the May 2003 French NSG paper, Iran has sought to acquire high density radiation shielding windows for hot cells and 28 remote manipulators from the French nuclear industry. Such equipment is designed for the extraction of plutonium from spent reactor fuel.
Heavy water technology
Iran has also sought to master heavy water technology. At a site in the Khondab area near Arak, which is approximately 150 miles southwest of Tehran, Iran plans to develop a heavy water production plant and a heavy water research reactor. The existence of the heavy water production plant was first revealed by the NCRI in August 2002 and verified by commercial satellite imagery in December 2002. Iran has informed the IAEA that the facility will produce about 16 tons of heavy water annually. However, according to the French NSG paper, the plant will have the capacity to produce 100 tons of heavy water annually. In December 2003, Iranian Vice President Gholareza Aghazadeh said that some parts of the plant were operational and that the project had made "80% progress in general and 90% in equipment and installation."
On May 5, 2003, Iran also announced plans to build a 40 megawatt thermal heavy water research reactor, called the Iran Nuclear Research Reactor (IR-40), at the same site. Construction of the reactor was expected to begin in June 2004. The reactor will be fueled by natural UO2 and will use heavy water as both a coolant and a moderator. The natural UO2 will be produced at a conversion facility in Esfahan (Isfahan) and made into fuel assemblies at a fuel manufacturing plant, also in Esfahan (Isfahan). Iran has admitted that it received some foreign assistance for the design of the reactor; the United States suspects that Russia provided the help.
According to Iranian authorities, the IR-40 will be used for research and development and for the production of radioisotopes for medical and industrial use. However, most states that have built this type of reactor, which is widely considered larger than necessary for research, have used it to produce bombs. The well-known precedents are Israel's Dimona reactor, supplied by France and Norway, and India's Cirus reactor, supplied jointly by Canada and the United States.
Every country trying to develop a nuclear weapon has faced two challenges. First came the need to produce a critical mass of fissile material—uranium 235 or plutonium—the metals needed to fuel a first-generation bomb. The second challenge was to produce a device that could cause the uranium or plutonium to explode in a nuclear chain reaction. This second process is called weaponization.
There have been no explicit reports that Iran has worked on weaponization. However, a number of activities and experiments Iran has undertaken, when coupled with its concealment efforts and its firm commitment to mastering the production of fissile material, suggest that Iran could be trying to make a nuclear device.
In September 2003, the IAEA discovered that Iran had produced polonium-210, a radioisotope with a half-life of 138 days. Iran conducted Po-210 production experiments in the Tehran Research Reactor (TRR) between 1989 and 1993 by irradiating bismuth metal. One of the best-known uses for Po-210 is as a neutron initiator in nuclear weapons. It also has civilian applications, such as in nuclear batteries. However, the IAEA considers the applications of Po-210-based nuclear batteries to be limited. Iran has said that the experiments were part of a study on neutron sources, but has been unable to provide documentation supporting this purported intent.
There have also been reports that Iran has sought deuterium gas from Russia. According to an intelligence report citing Russian sources that was circulated at the IAEA in July 2004, Iranian middlemen negotiated with companies in Russia to purchase deuterium gas after failing to produce it domestically. Deuterium gas is used, in conjunction with tritium, to boost the yield of fission bombs. Deuterium and tritium are hydrogen isotopes that release neutrons and energy when they fuse together in thermonuclear explosions.
In addition, the French intelligence services have reported that Iran has sought items useful for nuclear tests and simulation, including documentation on flash radiography equipment and pulse generators. Iran has also tried to purchase machines that can be used to fashion shapes of uranium or plutonium metal, such as isostatic presses and vacuum furnaces. And according to a May 2003 media report, a Swede of Iranian origin arranged the purchase of 44 high-voltage switches for Iran from Behlke Electronic GmbH, a German company. The switches, which were reportedly seized by German customs agents, could be used to trigger nuclear weapons.
Beyond its procurement efforts, the way in which Iran has organized and delegated its nuclear work to entities related to the defense ministry could suggest a military purpose. According to the IAEA, seven of the 13 workshops dedicated to the domestic production of centrifuge components are located on sites controlled by the ministry of defense.
Finally, if Iran received the same package of nuclear goods from the Khan network as did Libya—an eventuality that is widely suspected—then it could have received the same Chinese-origin bomb design. China is believed to have supplied Pakistan with a tested nuclear bomb design in the early 1980s. It is reportedly this design that the Khan network resold to Libya, along with documents in Chinese containing detailed instructions on how to manufacture parts for and assemble an implosion-type device.
Under the NPT, Iran must allow the IAEA to inspect its nuclear-related material so that the Agency can verify its peaceful use. This includes what the NPT calls all "source or special fissionable material" and all facilities where such materials are being used, processed or produced anywhere on its territory or anywhere under its control. Iran must also tell the IAEA about changes to its nuclear material inventory and submit inventory change reports when necessary. Finally, Iran is required to provide updated design information on its nuclear facilities and information on facilities where nuclear material is held or stored.
In a report to the IAEA Board of Governors in June 2003, following four months of Agency inspections in Iran, IAEA Director General Mohamed ElBaradei concluded that Iran "has failed to meet its obligations under its Safeguards Agreement with respect to the reporting of nuclear material, the subsequent processing and use of that material and the declaration of facilities where the material was stored and processed." Since then, the IAEA has documented a number of instances in which Iran violated its safeguards agreement by failing to report:
- The import of nearly 2,000 kg of uranium compounds (1,000 kg of UF6, 400 kg of UF4 and 400 kg of UO2) in 1991, allegedly from China;
- The processing of 1.9 kg of UF6 (imported in 1991) in centrifuges at the Kalaye Electric Company, which produced 1.2% enriched uranium;
- The conversion of 9.43 kg of the UF4 imported in 1991 into UF6 in a laboratory at the TNRC;
- The production of uranium metal in a laboratory at the TNRC in the 1990s using 376.6 kg of UF4 imported in 1991;
- The production of 2.5 kg of UF4 using UO2 imported in 1991;
- The irradiation of several grams of UO2 in the TRR and its subsequent processing in a laboratory at the TNRC;
- The irradiation of 3 kg of depleted UO2 targets in the TRR and subsequent plutonium separation experiments carried out in hot cells at the TNRC, in which about 200 micrograms of plutonium were produced;
- The import of 50 kg of natural uranium metal in 1993;
- The processing of 30 kg of the uranium metal imported in 1993 in two series of AVLIS enrichment experiments: first between 1999 and 2000 at the TNRC using 8 kg of uranium, and second at Lashkar Ab'ad between October 2002 and February 2003 using 22 kg of uranium metal;
- Pilot-scale laser enrichment operations at the TNRC and Lashkar Ab'ad using imported equipment and failing to provide design information on these sites;
- The transfer of nuclear equipment and material used in laser experiments to a waste storage facility at Karaj, and failing to provide design information on this new site;
- The use of uranium compounds imported in 1977 and exempted from inspection (U3O8 and depleted UO2) and yellowcake imported in 1982 in experiments at two laboratories at the Esfahan (Isfahan) Nuclear Technology Center;
- The use of depleted UO2, which Iran had originally declared as material lost during experiments, to produce UF4 in a laboratory at the TNRC;
- Research and development work on a more advanced centrifuge, known as the P-2, which should have been disclosed to the IAEA in Iran's October 2003 full nuclear report to the Agency. This omission violated Iran's obligations under the IAEA's Additional Protocol, which Iran had agreed to honor, pending ratification in the Iranian parliament.