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North Korea’s Nuclear Enrichment: Capabilities and Consequences

22 June 2011


North Korea’s pursuit of uranium enrichment should not, and has not, come as a surprise. The pre-eminence of Juche, the political thesis of Kim Il Sung, stresses independence from great powers, a strong military posture, and reliance on national resources. Faced with an impoverished economy, political isolation from the world, and rich uranium deposits, nuclear power—both civilian as well as military—fulfills all three purposes.

History and hindsight have shown a consistency in North Korea’s efforts to develop its own nuclear capability. One of the first steps North Korea took was to assemble a strong national cadre of nuclear technicians and scientists. In 1955, North Korea established its Atomic Energy Research Institute. In 1959, it signed an agreement with the Soviet Union to train North Korean personnel in nuclear related disciplines. The Soviets also helped the North Koreans establish a nuclear research center and built a 2 MW IRT nuclear research reactor at Yongbyon, which began operation in 1969.

Throughout the 1970s, North Korea continued to develop its nuclear capabilities, pursuing a dual track approach that was consistent with the idea of nuclear self-reliance. While engaging in discussions to obtain Light Water Reactors (LWRs) from the Soviet Union, North Korea proceeded with parallel studies on graphite moderated gas cooled reactors, using publicly available information based on the Magnox reactor design.[1] North Korea also carried out plutonium separation experiments at its Isotope Production Laboratory (IPL), and successfully separated plutonium in the same decade. The North Koreans worked on the design of a reprocessing plant for which, the chemical process was modeled after the Eurochemic plant.[2] When negotiations to acquire four LWRs from the Soviet Union failed, North Korea had already embarked on its indigenous nuclear program. Throughout the 1980s, North Korea constructed a 5MWe reactor, fuel fabrication plant, and a reprocessing plant at Yongbyon, with no known documented external help and with minimal foreign equipment procured. When the joint statement on the Denuclearization of the Korean Peninsula was concluded in December 1991, all three facilities had been fully operational for a number of years, with two additional (50 MWe and 200 MWe) graphite moderated gas cooled reactors under construction.

The Enrichment Route

North Korea’s closed society and isolationist position has made it immensely difficult to accurately gauge its nuclear activities. Pyongyang has gone to great lengths to hide much of its nuclear program, including its enrichment route. Nevertheless, there have been indications, including procurement related evidence, that point in the direction that North Korea has been actively pursuing enrichment since the mid-1990s, with likely exploratory attempts made up to a decade earlier. 

It is clear that North Korea received a key boost in its uranium enrichment capability from Pakistan through the A.Q. Khan network. Deliveries of P-1 and P-2 centrifuges, special oils, and other equipment from Pakistan to North Korea in the late 1990s were acknowledged by former Pakistani President General P. Musharraf in his memoirs, “In the Line of Fire.” President Musharraf also wrote that, separately, North Korean engineers were provided training at A.Q. Khan’s Research Laboratories in Kahuta under the auspices of a government-to-government deal on missile technology that had been established in 1994. In all likelihood, North Korea also received the blue prints for centrifuges and other related process equipment from the Khan network during that period of time.

In the late 1980s, North Korea acquired vacuum equipment from a German company. While such equipment was primarily meant for North Korea’s fuel fabrication plant then under construction, some of the vacuum pumps could have been used for enrichment experiments. But additional attempts made in 2002 to again acquire vacuum technology after the completion of the fuel fabrication plant strongly pointed to its use for enrichment purposes. Evidence of North Korea’s procurement activities in the late 1990s to the early 2000s showed its objective to achieve industrial or semi-industrial scale enrichment capacity, based on a more efficient Pakistani P-2 centrifuge design. In 1997, an attempt was made to acquire large amounts of maraging steel suitable for manufacturing centrifuges. In 2002/2003, North Korea successfully procured large quantities of high strength aluminum from Russia and the United Kingdom, another requirement in making centrifuges. A simple tally of the amounts and types of equipment and material sought by North Korea suggests plans to develop a 5000-centrifuge strong enrichment capacity. This appears consistent with a separate earlier enrichment offer A. Q. Khan had made to Libya.

For North Korea to have embarked on procuring equipment and materials meant for a (semi)industrial scale enrichment facility,[3] it is highly likely that the known Uranium Enrichment Workshop (UEW) at Yongbyon, which in reality approximates a full sized facility, is not the only one that exists. More workshops would have been needed to serve as test beds for pilot cascades of P-1 and P-2 centrifuges prior to (semi)industrial scale enrichment operations. While we have signs of North Korea’s enrichment goals, the final picture remains unclear given that the actual amount of items procured remains unknown. This problem is compounded by the fact that the North Koreans have and are continuing to source nuclear material and equipment from several parties. Moreover, there remains a high degree of uncertainty concerning the level of North Korea’s enrichment technology development. 

Enrichment Capabilities

In April 2009, after expelling IAEA inspectors, North Korea publicly announced for the first time that it was proceeding with its own enrichment program. To reinforce its intentions, North Korea followed up with a letter to the UN Security Council on September 3 to confirm that it was embarking on an enrichment phase. In November 2010, the North Koreans unveiled to Siegfried Hecker, a pre-eminent nuclear expert and former director of the Los Alamos Nuclear Laboratory, an enrichment facility in Yongbyon with 2000 centrifuge machines similar to the P-2 version, built with maraging steel rotors.[4] The scale, level of sophistication, and brazenness for the North Koreans to have built a (until then) secret enrichment facility at the same site of a previously IAEA-monitored building, caught international attention. The plant is proof of North Korea’s steady pursuit to include uranium enrichment as part of its domestic nuclear fuel cycle.

What does this mean in terms of North Korea’s enrichment production capacity?

2000 centrifuges when operating at full capacity are sufficient to annually produce 1.8 tons of low enriched uranium (LEU) or at 3.5% U-235. This projected output is consistent with the needs of a small LWR currently under construction that was also shown to Dr. Hecker. North Korea may however face some material and quality limitations that would restrict enrichment output.[5] On the other hand, such an enrichment plant can also easily be used for military purposes. There are two options to proceed with to make high enriched uranium (HEU): reconfigure the current 2000 centrifuge installation or add 800 new centrifuges for that purpose. An additional 800 centrifuges would be able to convert annually 1.8 tons of LEU to 40 kgs of HEU, an amount sufficient for the country to generate the necessary fissile material needed for one or two new nuclear bombs. Currently, North Korea is estimated to have between 25-40 kg of plutonium stocks, an earlier ingredient it had used to build and test its first bomb in 2006. Should North Korea use its current 2000-strong centrifuge capacity on an uninterrupted basis to produce 1.8 tons LEU annually, and have additional 800 centrifuges to enriched LEU further to HEU, we can expect its HEU stocks to exceed its current plutonium stockpile after three years.

Feed material in the form of uranium hexafluoride (UF6) is needed in sufficient quantities to power 2000 centrifuges. While no UF6 fabrication plants have been found in North Korea, its existence at undisclosed sites(s) has been traced as far as back in year 2000, when subsequent investigations revealed that North Korea had shipped UF6 to Libya. What this also means is that North Korea’s UF6 production was conducted in violation of the Agreed Framework and Comprehensive Safeguards Agreement that were in force during at that time. 

Implications and Consequences

On March 22, 2011, North Korea’s official news agency, KCNA, portrayed Libya’s decision to give up its nuclear weapons as a mistake that opened the country to NATO intervention following its domestic Arab Spring uprising. Such conclusions drawn by North Korea make an already difficult case to engage North Korea to give up its nuclear weapon deterrence that much harder. At the same time, the alternative of disengagement will in all likelihood bring about greater problems.   

In engaging North Korea, several key hurdles have to be tackled. First, North Korea shows a poor proliferation record. It was the suspected supply source of UF6 to Libya via the A.Q. Khan network. There is also mounting evidence that North Korea was involved in the construction of a secret nuclear reactor at Dair Alzour in Syria that was subsequently destroyed in 2007. It is plausible that North Korean personnel assisted Syria in building the reactor. There are also allegations of North Korean assistance provided to Myanmar’s emerging nuclear activities, which makes the point of proliferation of North Korean human expertise and know-how an added concern.

Second, North Korea has demonstrated its capability and intent to further develop the full range of its nuclear arsenal including: missiles, precision machining, working with high strength raw materials, and boosting uranium enrichment. Third, with North Korea publicly embarking on uranium enrichment, the prospect of achieving a denuclearized Korean Peninsula has dimmed even further. In contrast to the 1991 Joint Statement that denounced enrichment and reprocessing on the Korean Peninsula, North Korea has now reinterpreted the ban to cover only enrichment and reprocessing for military purposes, but not the right to enrich for civilian purposes.

What can be done?

We need to continue to step up international efforts at tightening export controls and nonproliferation efforts, making it more difficult for North Korea to obtain as well as proliferate in nuclear material and technology. We also need to do better in negotiating a comprehensive inspection and verification scheme when the Six Party Process addresses the verification phase. The Agreed Framework had limited the IAEA verification activities to Yongbyon, which gave North Korea the possibility to develop its enrichment and related capabilities elsewhere. That may have proven to be the best compromise at that time. But the consequences have been telling. Given the current nuclear situation in North Korea, a different approach would be needed if we want to progress substantially and significantly on properly safeguarding North Korea’s nuclear program. A full disclosure of the country’s historical and current nuclear activities will be necessary under any new agreement negotiated, alongside robust inspection rights for the IAEA. Avenues must also be sought to restrict and reduce North Korea’s sprint to build up on its nuclear arsenal. Added political will from all involved in the Six Party Talks will be needed to resolve the wider security and stability issue in Northeast Asia.

Engaging North Korea will continue to demand patience, while the possibilities for progress remain uncertain and uneven. But with much at stake, we have no choice but to get the end game right.

[1] Magnox reactors were designed in the United Kingdom originally to produce plutonium for nuclear weapons. The first such graphite moderated gas cooled reactor was built in the mid-1950s to Calder Hall in the UK. Design features of the reactor were subsequently declassified.

[2] Eurochemic was a research plant dedicated to the reprocessing of spent nuclear fuel. It was owned by thirteen countries which shared and widely published technologies developed. The plant, located in Dessel, Belgium, operated from 1966 to 1974.

[3] (Semi)industrial plants are used to demonstrate that the process is working properly to produce enriched  uranium before proceeding with a full scale expensive investment. At this stage one can still do adjustments to the process. In chemical the industry, this is often called to a pilot plant. (Semi)industrial plants have customarily about 1000 centrifuges when the full size enrichment plants can have tens of thousands of centrifuges.

[4] S. Hecker, Redefining Denuclearization in North Korea, The Bulletin of Atomic Scientists, December 20, 2010.

[5] North Korean engineers indicated to Dr. Hecker that the capacity of the centrifuges they had built was 4 kgSWU/year.(Separative Work Unit, SWU, is a measure of work expended during enrichment process). The performance of the North Korean centrifuge appears to be lower than 5 kgSWU/year which is often attributed to the Pakistani P-2 centrifuge.

Credit for photo of young North Korean girl: T.M. All rights reserved, used with permission.