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When negotiations began in 2003 between Iran and three European powers over its nuclear work, Tehran was struggling to assemble 164 uranium-enrichment centrifuges. The current round of negotiations that concluded successfully in Vienna on July 14, 2015, saw Iran in possession of more than 18,000 centrifuges. Even then, a nuclear-armed Iran was neither imminent nor inevitable.
Although a number of additional matters delayed the achievement of a deal at the eleventh hour, four key issues were at the core of international concerns over Tehran's nuclear activities:
Concern 1: Uranium enrichment
Iran's enrichment process is based on using centrifugal force to purify the active isotope in natural uranium. Depending on the level of purity to which it is enriched, the resulting fissile material could fuel nuclear reactors, be used medically or serve as bomb material. Iran has two main enrichment facilities and refines uranium to two levels. Less than 5 percent is used for reactors to create electricity, and 20 percent used in research reactors to produce medical isotopes.
The country has one nuclear power plant in Bushehr and one research reactor in Tehran. Given that fuel for Bushehr is provided by Russia and that Iran has already enriched enough fuel for the Tehran research reactor, many suspect that Iran's enrichment activities may not have exclusively innocent goals. The absence of a viable economic rationale for domestic enrichment — and the scarcity of uranium in Iran — exacerbates suspicions.
But Iranian leaders contend that eventual expansion of the country's peaceful nuclear program necessitates indigenous nuclear fuel production. If Iran were denied access to nuclear fuel on which it was dependent, it would lose at least $200 million per year for each idled reactor. Iran's enrichment activities are monitored by the International Atomic Energy Agency (IAEA), which also safeguards all the nuclear material in the country.
Iran's main enrichment facility is in Natanz and houses about 15,000 centrifuges. The majority of centrifuges Iran has installed there are the so-called first generation IR-1s. These are based on a 1970s design and are prone to regular mechanical breakdowns. Consequently, Iran has been working on developing more advanced centrifuges.
According to the most recent report from the IAEA, Iran had 1,008 IR-2m centrifuges installed by Aug. 28, 2013, and planned to install another 2,000 in the next few months. These machines are not yet enriching uranium but are estimated to be at least three times as efficient. Iran's second enrichment facility, Fordow, is under a mountain near the holy city of Qom and is believed to be impervious to an Israeli airstrike. Iran has installed nearly 3,000 IR-1 machines there but is currently operating only one-third of them.
Concern 2: Fissile material stockpile
Accumulation of enriched uranium in Iranian facilities is another source of concern, as such material could more rapidly be further refined to reach weapons grade (above 80 percent). As of Aug. 28, 2013, Iran had 6,774 kilograms of 3.5 percent and 185 kilograms of 20 percent enriched uranium.
With further enrichment — if Iran expelled inspectors — that stockpile could be turned into material for five nuclear weapons in six months to a year. Iran's accumulation of uranium enriched to 20 percent is particularly worrisome, as that level of enrichment reduces by more than 90 percent the time it would take to turn natural uranium into bomb material.
Tehran, however, has thus far kept the size of its 20 percent stockpile below the red line set last year by Israel's Prime Minister Benjamin Netanyahu, which is about 250 kilograms (enough for one bomb if re-enriched). It has done this by oxidizing enriched uranium and converting it into fuel rods for reactors, a process that renders weaponization far more difficult.
Concern 3: Heavy-water reactor
Iran is constructing a heavy-water research reactor in the city of Arak. The reactor uses natural uranium as fuel; once operational, it will produce about 9 kilograms of plutonium every year, which is sufficient for 1 1/2 bombs. This can open a second path — followed by most nuclear proliferators — to nuclear weapons.
Separating plutonium from a reactor's spent fuel rods, however, requires a reprocessing facility that Iran neither currently has nor has demonstrated any intention of building. But this might not matter to Israel, which twice before has attacked suspected reactors in countries in the region — in Iraq in 1981 and in Syria in 2007 — before their completion, since striking an operational reactor would result in an environmental catastrophe.
Concern 4: Past activities
Iran's uranium enrichment program was born in secret through the acquisition of technical drawings, manufacturing instructions and samples of components for centrifuges from the father of Pakistan’s atomic bomb and infamous proliferator, AQ Khan.
Iran's construction of undeclared nuclear enrichment and heavy-water facilities was exposed in 2002 by an exiled opposition group, triggering an international crisis.
Nine years later, the IAEA detailed charges that before 2003, Tehran experimented with technologies critical for the development of nuclear warheads, warning that some such research work may be ongoing.
While the Nuclear Non-Proliferation Treaty entitles Iran to enrich and stockpile uranium and construct a heavy-water reactor for civilian purposes, at issue is whether Tehran is in compliance with all its responsibilities under Article II of the treaty, which requires signatory nations to refrain from seeking or receiving any assistance in the manufacture of nuclear weapons or other nuclear explosive devices.
Six U.N. Security Council resolutions have demanded that Iran suspend these activities until international confidence is restored in the purely peaceful nature of its program, and a decade of negotiations between Iran and Western powers has thus far failed to resolve the nuclear standoff.
So how close is Iran to being able to build nuclear weapons — assuming that is its intention?
Guessing Iran's timeline for attaining nuclear weapon status has been a popular pastime of analysts, pundits and politicians for almost two decades. But most of these estimates are based on misplaced alarmism, for three main reasons:
Reason 1: International inspections
No state has built nuclear weapons while under scrutiny of in-country IAEA inspectors. In fact, of the five countries that developed nuclear weapons in the past four decades, four (Pakistan, India, South Africa and Israel) were not signatories of the Nuclear Non-Proliferation Treaty and therefore were never under IAEA inspection, and North Korea expelled the inspectors before testing its nuclear device.
IAEA inspectors visit Iran's nuclear facilities almost weekly. And time favors the inspectors. Alarmist warnings about Iran reaching breakout capability — the ability to process low-enriched uranium into weapons grade fissile material — omits the simple fact that if Iran decided to produce weapons-grade uranium, it would have to reconfigure its centrifuge cascades.
That process usually takes one to two weeks and would undoubtedly be detected by the IAEA. It is extremely unlikely that Iran could even buy time by delaying the inspectors' visit through pretexts, given that such action is likely to prompt international opprobrium and even serve as a casus belli.
Iran can’t begin producing bomb material without tripping a wire that would give the other nations several weeks to react before it could create fissile material for a single bomb, and turning such material into a deliverable warhead would take would take at least a year.
Reason 2: The cost-benefit rationale
A country reaches the military nuclear threshold when it has the capacity to manufacture one or more nuclear weapons within weeks. But it defies strategic logic for a country to accept risks of a military confrontation with more powerful adversaries simply in order to develop a single crude nuclear device.
To acquire real nuclear deterrence, Iran would need a deployable nuclear arsenal, not just enough material for one bomb. It would need to test a nuclear device and marry it with an appropriate delivery vehicle. And it is nearly impossible that Iran could reach such a capability in less than a year without being detected and stopped by the U.S. or Israel.
All previous Iranian efforts to conceal nuclear activities were exposed in their nascent stages. Likewise, it is useful to remember than given the United States' significant standing capabilities in the region, it would take less than 24 hours for the U.S. to launch military strikes in response to any such undertaking.
To acquire real nuclear deterrence, Iran would need a deployable nuclear arsenal, not just enough material for one bomb.
Reason 3: The lack of a political decision
Iranian leaders have pledged to never make nuclear weapons, which they consider a violation of Islam. But more important, according to James Clapper, the United States' director of national intelligence, Iran’s leaders have not yet decided to build nuclear weapons. The U.S. and Israeli intelligence communities are reasonably confident of their ability to detect such a decision.
In contrast to lack of evidence of any political decision by Iran to cross the nuclear Rubicon, the Iranian government has provided plenty of evidence that it wants a nuclear deal. Besides verbal declarations by its leadership, a number of Iranian decisions in managing nuclear work have been read as signaling a desire to avoid provoking confrontation. For example, Tehran has converted approximately 60 percent of its 20 percent enriched uranium stockpile to uranium oxide, which is less prone to proliferation, as its further enrichment requires weeks of chemical processing detectable by the IAEA.
Tehran could double its enrichment at Fordow by turning on nearly 2,000 centrifuges that it has installed at the facility but are not yet operating. The same applies to the IR-2m machines. Iran has also delayed the previously announced completion date (the first quarter of 2014) of the Arak reactor.
Analysts see these moves as signs that Tehran is preparing bargaining chips to negotiate relief from the Western sanctions that have debilitated its economy. As Clapper said, "Iran's nuclear decision-making is guided by a cost-benefit approach, which offers the international community opportunities to influence Tehran."
With 17 declared nuclear facilities and nearly five decades in the making, Iran's nuclear program is quite extensive. It has also been expensive, given the cost of harsh sanctions that the program has incurred. Yet it has become a point of national pride because Iran has developed indigenous nuclear know-how.
That fact alone means that Iran’s nuclear program cannot be wished away or bombed away. U.S. military and intelligence chiefs have made clear that the only sustainable solution is one in which Tehran chooses to refrain from building nuclear weapons, under an accord that thickens the barrier between civilian and military nuclear activity in Iran. Such an accord would limit the scale and scope of Iran's nuclear work, enhance the IAEA's monitoring capabilities and allow Iran to rejoin the international community.
Ali Vaez is the senior Iran analyst at the International Crisis Group, having previously headed the Iran project of the Federation of American Scientists in Washington, D.C., focusing on Iran’s nuclear and missile programs.