Negotiating with the North: Doubting Its Enrichment Claims

Following its May 2009 nuclear test and the subsequent condemnation of the U.N. Security Council, North Korea revealed that it was developing uranium enrichment technology and that its work had entered the experimental phase. 1 North Korea described the program in a September letter to the Security Council, saying “experimental uranium enrichment has been successfully conducted to enter into the completion phase.” 2 Though vague about the program's scope and contents, these statements were the first time that Pyongyang publicly disclosed its pursuit of an enrichment program.

The North's clandestine procurement of uranium enrichment technology has played a central role in U.S.-North Korean relations during the past decade. In 2002, then-U.S. Assistant Secretary of State James Kelly confronted senior North Korean officials with evidence that Pyongyang was attempting to procure centrifugerelated materials and equipment, triggering a second nuclear crisis on the Korean Peninsula. This revelation led to the dissolution of the 1994 Agreed Framework between Washington and Pyongyang, which had defused the first North Korean nuclear crisis. The enrichment issue has eluded negotiators ever since.

Lost in the uncertainty surrounding the North's uranium enrichment program has been a clear understanding of Pyongyang's motivation for developing it. Back in the mid- to late 1990s, North Korea might have had reason to develop such a program. The terms of the Agreed Framework, if it had been successfully implemented, would have closed down the North's reprocessing-based weapons program; as such, it may have been tempted to clandestinely develop an alternative route to a nuclear weapon. And it was around this time that the North Koreans are thought to have acquired technologies and know-how from the illicit A. Q. Khan nuclear network–although some believe that this procurement occurred much earlier.

The Agreed Framework's dissolution is likely to have altered the North's motivations. By the time International Atomic Energy Agency (IAEA) inspectors returned to North Korea in the summer of 2007, after a hiatus of more than four years, Pyongyang contended that it had performed two rounds of reprocessing (one in 2003 and one in 2005), using spent fuel irradiated in the 5-megawatt-electric reactor located at the Yongbyon nuclear complex. In its June 2008 classified declaration to the other governments participating in the Six-Party Talks (the United States, South Korea, Japan, China, and Russia), Pyongyang reportedly revealed that its reprocessing efforts yielded approximately 30.8 kilograms of plutonium–all but 2 kilograms of which it fashioned into nuclear weapons. (The North claimed that the 2 kilograms were used in its October 2006 nuclear test.) The precise amount of plutonium that Pyongyang declared was never publicly disclosed. 3

After the Six-Party agreement that brought IAEA inspectors back into North Korea collapsed in April 2009, the North decided to restart its reprocessing. Last November, North Korea asserted that it had “successfully completed the reprocessing of 8,000 spent fuel rods” that were discharged in accordance with the October 2007 Six-Party agreement and that “noticeable successes have been made in turning the extracted weapon-grade plutonium for the purpose of bolstering up the nuclear deterrent.” 4

The precise status of the North's uranium enrichment throughout this period is unknown. But from a historical and technical standpoint, there is good reason to believe that Pyongyang's pursuit of an enrichment capability is part of a larger pattern of deception. Despite the North's claim to have a successful experimental enrichment program, the program may turn out to be, at best, pilot scale, or at worst, a ruse. Rather than attempting to build a production enrichment program, Pyongyang may have embellished its nuclear capabilities to inflate the threat it poses and to add one more negotiating card for future deals.

A technical viewpoint. Nuclear aspirants have two general routes to produce fissile materials for a nuclear weapon: uranium enrichment or plutonium reprocessing. A basic nuclear device, whether it is a gun-type design or an implosion-type design, requires considerably more highly enriched uranium (HEU) than it does plutonium. The IAEA defines 8 kilograms of plutonium and 25 kilograms of HEU as “significant” quantities, meaning that approximately that amount of nuclear material is needed to make a nuclear weapon, though this estimate seems conservative in light of advanced bomb-making technology. 5 In “perfected” bombs only about 4 kilograms of plutonium are needed, compared to the 60 kilograms of HEU needed for gun-type bombs. 6

Despite the North's claim to have a successful experimental enrichment program, the program may turn out to be, at best, pilot scale or, at worst, a ruse. Rather than attempting to build a production enrichment program, Pyongyang may have embellished its nuclear capabilities to inflate the threat it poses and to add one more negotiating card for future deals.

Even if an aspiring nuclear weapon state were to use HEU in an implosion-type device–the route taken by China for its first nuclear test in 1964–the amount of HEU needed is still greater than the requisite amount of plutonium, were a comparable design used. The London-based International Institute for Strategic Studies has assessed that North Korean weapons are based on a first-generation implosion design, the logical choice for states in the initial stage of nuclear weapon development. Therefore, Pyongyang would need 5-8 kilograms of weapon-grade plutonium or 20-25 kilograms of weapon-grade HEU for each implosion device. These estimates roughly correspond to the amounts of fissile material used by the nine current nuclear weapon states in their early designs. 7

The amount of HEU needed for an implosion-type bomb could be further reduced by employing sophisticated engineering techniques. One cannot rule out the possibility that North Korea could improve its weapons technology in order to produce low-kiloton devices that require less HEU, yet it is highly unlikely that Pyongyang could achieve the level of U.S. design sophistication within such a short time period. Additionally, North Korea has maintained a successful reprocessing program for more than two decades and has churned out many kilograms of weapon-grade plutonium. The combination of the North's experience separating plutonium and the need for less plutonium than HEU to build a rudimentary weapon provides little incentive for Pyongyang to seriously invest in enrichment.

Another likely technical disadvantage in North Korea's pursuit of a uranium enrichment capability is that the larger missile pay-load resulting from a rudimentary HEU nuclear weapon would limit its range. In general terms, a plutonium bomb would offer Pyongyang a better chance of making a warhead small and light enough to be loaded onto its nascent long-range missile force. The April 2009 test-launch of a Taepodong-2 rocket demonstrated the North's progress toward a long-range missile capability: The three-stage vehicle's second stage successfully separated. Yet, its last stage failed to push the rocket's payload into orbit. Following the test, Pyongyang reiterated its goal of taking additional “self-defensive” steps, including additional test-firings of intercontinental ballistic missiles (ICBMs). 8 The overriding motivation behind Pyongyang's development of ICBMs is to threaten the United States with nuclear weapons. And the North understands that smaller, lighter plutonium-based devices present the best opportunity to do so.

In short, the most efficient and cost-effective use of North Korean security resources would be for Pyongyang to invest in its existing reprocessing program. The North can support additional plutonium production for use in nuclear weapons, above and beyond the material it obtained from the recent reprocessing of 8,000 spent fuel rods. For instance, it could reconfigure and reload the inventory of fresh fuel stored in Yongbyon. Currently, Yongbyon contains 2,400 fuel rods configured for the complex's 5-megawatt-electric reactor and an additional 12,400 fuel rods that are presently configured for the site's nonfunctional 50-megawatt-electric reactor that could be easily converted into fuel for the smaller reactor. It also could restart construction of its 50- and 200-megawatt-electric plutonium-producing reactors, whose construction was suspended as part of the Agreed Framework. And it could excavate and mill more natural uranium to make additional fuel for its bomb-making complex.

Yongbyon's facilities are outdated and aging, but they are workable. In April 2009, North Korea rescinded the agreement it signed to disable the site's 5-megawatt-electric reactor, reprocessing facility, and fuel fabrication facility. If the 5-megawatt-electric reactor were refueled and a cooling system were reestablished, either through the rebuilding of a cooling tower or an underground system, the reactor could be made operable. After all, the reactor, which began operating in 1986, is relatively young compared to other plutonium-producing reactors such as India's CIRUS reactor or Israel's Dimona reactor, which began operating in 1960 and 1964, respectively. The North's reprocessing facility seems to be already up and running, and the fuel fabrication facility can be refurbished.

There is a possibility that North Korea already has a pilot-scale enrichment facility consisting of dozens or hundreds of early-generation centrifuges. Yet as demonstrated above, the relative advantages of plutonium over HEU suggest that it would have been impractical for Pyongyang to dedicate substantial resources to its centrifuge program. In addition, mastering centrifuge development and operation typically requires the overseas procurement of key machine parts, such as high-strength aluminum, maraging steel, rotors, frequency inverters, and balancing machines, to name a few. Acquiring these parts would have been challenging for North Korea, considering international nuclear export controls and U.N. Security Council Resolutions 1718 and 1874, which ban the transaction of these sensitive nuclear items to the North.

Historical viewpoint. While North Korea might have little reason to make major investments in an enrichment program, it is worth analyzing the technical decisions of other nuclear weapon states to fully appreciate the trajectory of the North's nuclear weapons program. During the Cold War, the five nuclear weapon states recognized by the Nuclear Non-Proliferation Treaty (NPT) explored and mastered either simultaneously, or sequentially, uranium enrichment and plutonium reprocessing technologies in order to produce fissile materials for their nuclear weapons. In contrast, the careful technology choices of the three de facto nuclear powers (Israel, India, and Pakistan) demonstrate that if a choice has to be made, the plutonium reprocessing route is superior, as plutonium is a more efficient fissile material for bombs on a weight-for-weight basis than HEU, and it is generally considered cheaper to produce fissile material through a reactor and a reprocessing plant than by building an enrichment facility. To this day, India and Israel seem content with their reprocessing programs, and evidence is scant that either is willing to siphon precious resources to pursue the costly and complicated uranium enrichment route, except for the limited scope of enrichment-related activities that could bolster weapon yield or support naval use.

The overriding motivation behind Pyongyang's development of ICBMs is to threaten the United States with nuclear weapons. And the North understands that smaller, lighter plutonium-based devices present the best opportunity to do so.

India launched its nuclear energy development program shortly after it became independent in 1947. From the outset, New Delhi considered using plutonium to power future nuclear reactors because the country had limited uranium deposits. Canada and the United States both contributed resources and expertise to what became known as the CIRUS reactor. This proliferation-prone reactor produces spent fuel containing weapon-grade plutonium after a relatively short time. When CIRUS came online in 1960, India had already begun constructing a reprocessing facility at the same site, Trombay, with U.S. assistance. In 1964, shortly after the plant's completion, Indian scientists successfully extracted the first batch of plutonium from fuel rods irradiated at CIRUS.

New Delhi decided to develop nuclear weapons using CIRUS-derived plutonium after its 1962 war with China and Beijing's 1964 nuclear test. The Indian nuclear weapons program proceeded largely unnoticed, until India detonated one nuclear device in 1974. 9 It is estimated that New Delhi continues to produce plutonium at a combined rate of about 30 kilograms annually from both CIRUS and a 100-megawatt Dhruva heavy water reactor that was added to the weapons program in 1985, and that its stockpile of weapon-grade plutonium stands at 680 kilograms. 10

India decided to build pilot-scale centrifuge enrichment plants in Trombay and Mysore in 1985 and 1990, respectively, and the plants are believed to be operating with no more than several hundred centrifuges combined. New Delhi's possible motives for maintaining a small enrichment program include: producing fissile materials for use in thermonuclear bombs, fueling its nuclear submarines with low-enriched uranium enriched, and matching Pakistan's centrifuge technology for psychological purposes. It is worth noting the tangential nature of these potential motives, as India's reprocessing program has already provided an effective, reliable foundation for New Delhi's nuclear forces. 11

Like India, Israel also decided to use reprocessing technology, rather than enrichment technology, to develop nuclear weapons. Israel contemplated acquiring a nuclear weapon capability as soon as it was established in 1946. In the late 1950s, France provided Israel with a 26-megawatt plutonium production reactor, the necessary natural uranium fuel and heavy water, and an underground reprocessing plant, all built near the town of Dimona in the Negev Desert. The reprocessing plant started operating in 1964, and by the time the Six-Day War was fought in 1967, Israel was thought to have two nuclear bombs. 12

According to the International Panel on Fissile Materials, Israel possesses approximately 600 kilograms of plutonium, sufficient material for between 100 and 150 weapons. 13 The Nuclear Threat Initiative suggests that Israel's nuclear weapon inventory is less than 100 and that its stockpiled plutonium could be used to assemble more weapons if necessary. There is little credible public information on Israel's uranium enrichment capability. Yet there is no convincing reason to believe that Israel has heavily invested in an industrial-scale enrichment program. At best, Israel has a pilot-scale enrichment facility, similar to India's.

Pakistan, on the other hand, pursued uranium enrichment initially to build its first-generation weapons and then plutonium reprocessing for subsequent generations of weapons. Islamabad's nuclear weapons program first began in 1974 when France agreed to supply it with a reprocessing facility. In the aftermath of the Indian nuclear test, however, the United States pressured France to drop the contract. Determined to build nuclear weapons, Islamabad capitalized on the expertise that A. Q. Khan brought back to Pakistan after working with the URENCO enrichment consortium in the 1970s. By 1981, under Khan's guidance, Pakistan had set up about 1,000 centrifuges in the Kahuta Research Laboratory near Islamabad. In 1982, Pakistan allegedly obtained an implosion-type bomb design and 50 tons of weapon-grade HEU from China, and by 1985, Islamabad had its first atomic bomb. 14

Pakistan has an estimated stockpile of between 70 and 90 nuclear weapons and is thought to have produced approximately 2 tons of HEU and 90 kilograms of weapon-grade plutonium as of early 2008. Like other nuclear weapon states, Pakistan has been improving its weapon designs, transitioning from its early HEU-based weapons to plutonium-based designs. Evidence suggests that the plutonium in use in Pakistan's arsenal is derived from fuel burned in Pakistan's 40-50 megawatt heavy water-moderated plutonium production reactor in Khushab, which was completed in 1998, and the pilot reprocessing plant in operation near Rawalpindi.

The countries negotiating with the North should be careful not to play into Pyongyang's hands on the matter–i.e., buying the North Korean government off with aid or political compromises in exchange for concessions on a uranium enrichment program that is either incredibly nascent or a complete fabrication.

Islamabad is building two additional heavy water reactors at the Khushab site and a second reprocessing plant in Rawalpindi. Work may also have resumed on a partially built separation plant that dates back to the 1970s. 15 “The types of facilities under construction,” Robert Norris and Hans Kristensen wrote in the Bulletin's September/October 2009 Nuclear Notebook, “suggest that Pakistan has decided to supplement and perhaps replace its heavy uranium-based weapons with smaller, lighter plutonium-based designs that could be delivered further by ballistic missiles.” 16

Final thoughts. North Korea has said that it “will only possess [a] nuclear deterrent to such an extent as to deter military attack and its threat against our country,” a stance reminiscent of the minimum credible deterrence doctrine of other nuclear powers. 17 Regardless of how many bombs will be enough to accomplish this goal, Pyongyang is likely to continue its saber rattling. Having reprocessed the last group of spent fuel from the 5-megawatt-electric Yongbyon reactor, the North Koreans could conduct additional nuclear tests, which could allow them to improve their bomb designs or test-launch additional long-range missiles.

One plausible rationale that would explain North Korean development of a full-scale enrichment capability is that the North intends to use the capability as leverage in negotiations with the United States and other countries. But so far, Pyongyang has been able to extort benefits from its negotiating partners without the enrichment program being on the table. As part of the September 2005 Joint Statement and subsequent Six-Party agreements, North Korea committed to abandoning all of its nuclear weapons and existing nuclear programs, returning to the NPT, and again accepting IAEA safeguards; in return, the United States promised a full package of security and economic benefits that Pyongyang has craved for decades, including a nonaggression commitment, the normalization of bilateral relations, economic cooperation, energy assistance, and support for creating a new security architecture in Northeast Asia. Moreover, Washington has already removed North Korea from its list of state sponsors of terrorism and stopped applying the Trading with the Enemy Act against it, both of which have been high on Pyongyang's agenda. So what more could North Korea extort from the international community in exchange for action on a clandestine enrichment program?

Whatever the state of the North Korean uranium enrichment program, it should be subjected to IAEA safeguards and international verification in the hopes of ending the secretive program once and for all. For instance, besides preventing the sale of sensitive nuclear items to the North as required by U.N. Security Council Resolutions 1718 and 1874, the Nuclear Suppliers Group (NSG) could take additional steps to constrain the North Korean nuclear program. In particular, the NSG should consider drawing up a watch list of uranium exploration equipment that may be useful to North Korea. Pyongyang has vast uranium deposits–an estimated 26 million metric tons–and its long-term nuclear strategy is predicated on the continued supply of natural uranium. Denying Pyongyang advanced exploration tools and stopping uranium sales would be sensible precautionary measures.

That said, the countries negotiating with the North should be careful not to play into Pyongyang's hands on the matter–i.e., buying the North Korean government off with aid or political compromises in exchange for concessions on a uranium enrichment program that is either incredibly nascent or a complete fabrication. After all, history and technological savvy dictate that such a program would be both counterproductive and inefficient for Pyongyang.