5 MW(e) Graphite-Moderated Reactor at Yongbyon

5 MW(e) Graphite-Moderated Reactor at Yongbyon (Courtesy: Keith Luse, United States Senate)

North Korea Nuclear Update

 May 2016

By Jonathan McLaughlin


North Korea continues to aggressively develop its nuclear and ballistic missile capabilities. Since the start of 2016, it has conducted its fourth nuclear weapons test, tested two ballistic missile engines, a long-range rocket, and a submarine launched ballistic missile (SLBM). These acts have been accompanied by a series of belligerent statements by Pyongyang. More provocations may be on the way. In March, North Korean state media warned that another nuclear test would be conducted soon.

The heart of North Korea’s nuclear program is the Yongbyon Nuclear Research Center. Pyongyang is producing both plutonium and highly enriched uranium (HEU) at Yongbyon, and continues to expand operations there. Such progress has taken place despite an international sanctions regime designed to deny Pyongyang access to the funding and equipment it needs to sustain its nuclear program. North Korea has managed to circumvent sanctions through a series of procurement networks as well as lax enforcement by some countries.

2016 Test

North Korea conducted its fourth nuclear weapons test in January 2016, claiming that it tested a thermonuclear (hydrogen) bomb. Earlier nuclear tests were conducted in February 2013, May 2009, and October 2006. Estimates of the yield of the 2016 test range from 6-10 kilotons. The U.S. National Intelligence Director reported to Congress shortly after that test that the low-yield “is not consistent with a successful test” of a hydrogen bomb. However, another U.S. official familiar with the evidence told CNN that the device was likely to have contained components associated with a hydrogen bomb.

North Korea’s first two tests were believed to have been of plutonium-based devices. The fuel used in the two most recent tests is not known.

Stockpile and Capabilities

Assessments of the current size of Pyongyang’s arsenal of nuclear warheads vary considerably, from as few as six to as many over 20 warheads. The disparities among these estimates are due in large part to differences regarding the assumed amount of fissile material used per weapon. In any case, North Korea has likely had a stockpile of nuclear warheads for some time. In 2004, U.S. intelligence agencies reportedly assessed that it had anywhere from “’possibly two’ to at least eight” nuclear warheads.

Stockholm International Peace Research Institute (SIPRI) estimates that North Korea has six to eight nuclear warheads, assuming five kilograms (kg) of plutonium per warhead. A Chinese nuclear expert associated with the China Institute of International Studies reportedly indicated that North Korea may have as many as 20 warheads. The analyst further claimed that Pyongyang has the capacity to double its arsenal within a year’s time. The Institute for Science and International Security (ISIS) estimates that Pyongyang has 10 to 16 warheads, assuming three to four kg of plutonium per warhead and 15-25 kg of weapons grade HEU per warhead. The Nonproliferation Policy Education Center (NPEC) assesses that the number could be anywhere from four to over 20 warheads, assuming eight kg of plutonium per warhead and 25 kg of weapons grade HEU per warhead.

As with North Korea’s arsenal of nuclear warheads, estimates of the size its stockpile of fissile material vary, reflecting a high degree of uncertainty. The International Panel on Fissile Materials (IPFM) estimates that Pyongyang has produced approximately 30 kg of separated plutonium as of the end of 2014, and assesses that the enrichment facility at Yongbyon is capable of producing HEU. ISIS estimates that North Korea has produced approximately 30-34 kg of separated plutonium and anywhere from 100-240 kg of weapons-grade HEU. Dr. Siegfried S. Hecker, former director of Los Alamos National Laboratory, estimated in October 2013 that North Korea has produced approximately 24-42 kg of plutonium. He has also assessed that the enrichment plant (prior to its expansion) could produce up to 40 kg of HEU per year, if the cascades were reconfigured.

North Korean leader King Jong Un announced in March 2016 that his country has successfully developed a miniaturized nuclear warhead capable of being mounted on a ballistic missile. In March North Korean state media also released images of Kim inspecting what is believed to be a mock-up of a miniaturized nuclear warhead. Washington is skeptical of Pyongyang’s miniaturization claims. Still, the head of North American Aerospace Defense Command (NORAD) recently informed Congress that “it’s the prudent decision on my part to assume that [North Korea] has the capability to…miniaturize a nuclear weapon and put it on an ICBM,” while acknowledging that an attack with such a weapon on the U.S. homeland is not likely to succeed. South Korea reportedly assesses that it will take several years before Pyongyang masters miniaturization technology.

Currently, North Korea’s longest-range deployed ballistic missile is the Nodong. With a maximum range of 1,250-1,300 km (approximately 775-800 miles), the Nodong is capable of reaching all of South Korea and parts of Japan.

Fissile Material Production Facilities


The Yongbyon Nuclear Research Center, located approximately 54 miles (90 km) north of Pyongyang, is North Korea’s main nuclear complex. It houses all of its key (known) facilities, including its plutonium production reactor, reprocessing center, and enrichment plant. Below is a list of its major facilities:

5 MW(e) Experimental Nuclear Power Plant: a graphite-moderated reactor. This reactor, which has been in operation since 1986, is North Korea’s most important nuclear facility, providing it with plutonium.

Radiochemical Laboratory: a reprocessing facility, where plutonium and uranium are extracted from irradiated (spent) nuclear fuel. It has a production capacity of 100-150 tons of heavy metal per year.

Nuclear Fuel Fabrication Plant: used to convert uranium oxide (U3O8 or “yellowcake”) into uranium metal, and has housed uranium dioxide (UO2) powder, fuel rods, and fuel rod cores.

Uranium Enrichment Plant: reportedly contains 2,000 centrifuges in six cascades with an enrichment capacity of 8,000 kg seperative work units (SWU) per year.

Light-water reactor (under construction): reportedly has a capacity of 100 MW(th) (25 to 30 MW(e)).

Nuclear fuel rod storage facility.

Operations have continued at Yongbyon in recent years. In April 2013, North Korea announced that it would restart its 5 MW(e) reactor and uranium enrichment plant. The U.S. Director of National Intelligence assessed in January 2014 that Pyongyang has restarted the reactor, which was shut down in 2007, and is expanding the enrichment facility. In February 2016, he assessed that it could start recovering plutonium from the reactor’s spent fuel “within a matter of weeks to months.” Satellite imagery confirms that North Korea is expanding the uranium enrichment plant, reportedly by adding 2,000 centrifuges, thus doubling its enrichment capacity.

North Korea reprocessed 8,000 spent fuel rods at the Radiochemical Laboratory after expelling international inspectors in 2009. More recently, satellite imagery from March 2016 reportedly detected exhaust plumes emitting from the lab’s steam plant on several occasions, suggesting that operations are underway there, or will be soon.         

In its August 2012 safeguards report, the International Atomic Energy Agency (IAEA) indicated that North Korea had made “significant progress” in the construction of the light water reactor at Yongbyon. The facility was reportedly still under construction as of March 2016.

Yongbyon will remain a reliable source of the plutonium and HEU North Korea needs to expand its nuclear arsenal. The 5 MW(e) reactor is producing recoverable plutonium, the reprocessing facility is functional, and the enrichment facility is online.

Mines and Mills

North Korea has two known uranium mines: Wolbisan and Pyongsan. In addition, it has two known uranium mills: Pakchon Uranium Concentrate Plant and Pyongsan Uranium Concentrate Plant. The IAEA has not visited these sites since 1992, relying on satellite imagery to monitor activity there. Satellite imagery analysis by private experts has concluded that the Pyongsan mill is undergoing “significant refurbishment,” suggesting that North Korea plans to mine and mill a “significant amount” of uranium from the Pyongsan mine and possibly other locations.


North Korea withdrew from the Nuclear Nonproliferation Treaty (NPT) in 2003, and expelled international inspectors from the country in 2009 after the collapse of the six party talks. In response to Pyongyang’s refusal to cease its nuclear and ballistic missile programs, the international community has imposed sanctions. After the first nuclear test in 2006, the U.N. Security Council adopted resolution 1718. Among other measures, the resolution prohibits the import to or export from North Korea of battle tanks, heavy artillery, combat aircraft systems, warships, items applicable to its nuclear or ballistic missile programs, and luxury goods. After each subsequent test, the Security Council adopted additional sanctions, further restricting North Korea’s access to sensitive or restricted materials and technology, and to the global economy.

The latest (and most stringent) measures were adopted by the Security Council in March 2016 in response to the January 2016 test. Resolution 2270 requires the inspection of all cargo going to or coming from North Korea or being shipped by a North Korean national, and imposes other prohibitions on North Korean vessels and aircraft.

The Security Council resolutions also impose measures, including an asset freeze, transaction prohibition, and travel ban, against designated organizations and individuals connected to Pyongyang’s nuclear and ballistic missile programs. To date, 28 individuals and 32 organizations have been designated by the Security Council.

These measures have targeted some of the main entities in charge of North Korea’s nuclear program. For example, the Ministry of Atomic Energy Industry (aka General Bureau of Atomic Energy)*, which was designated in 2009, oversees North Korea’s nuclear program, including activities at Yongbyon. In 2013, it was put in charge of modernizing the country’s atomic energy industry. It is currently in charge of the day-to-day operations of the nuclear weapons program and oversees a number of nuclear-related organizations and research centers. Another entity, the Munitions Industry Department (MID), which was designated in 2016, oversees North Korea’s weapons production and R&D programs. MID planned and prepared the January 2016 nuclear warhead test. According to a 2010 UN Panel of Experts on North Korea report, it has also been involved in overseeing operations at Yongbyon.

The Security Council has also designated producers of machinery and components for the nuclear program. One such entity is Korea Ryonha Machinery Joint Venture Corporation, which was targeted in 2013. Ryonha is North Korea’s primary producer of computer numerically controlled (CNC) machines, including multi-axis CNC machines, which are important for the production of nuclear weapons. Pyongyang has been clear about the role that CNC technology plays in developing its arsenal. Another production entity designated by the Security Council is Korea Hyoksin Trading Corporation. Hyoksin, which was targeted in 2009, is involved in the development of unconventional weapons. It produces electronics and instruments for measuring and testing.

Other entities supporting North Korea’s nuclear program have not been designated. One example is Kim Chaek University of Technology. This institute produces concentrated nitric acid (CNA)- resistant low-carbon stainless steel, which is used in plutonium extraction equipment and spent fuel storage vessels. The University has also trained personnel at Yongbyon.

A number of governments, including the United States, Japan, and the European Union, have gone beyond the U.N. measures, imposing autonomous sanctions that restrict trade with Pyongyang, and freeze the assets of dozens more individuals and entities. Combined, these autonomous measures and the Security Council resolutions severely restrict North Korea’s access to foreign goods and currency.

However, these measures have failed to change Pyongyang’s behavior or sufficiently hinder its activities abroad, a situation highlighted by the U.N. Panel of Experts. The Panel periodically evaluates the efficacy of the sanctions regime. In its latest report from February 2016, it indicates that, despite the strength of existing measures, Pyongyang has still managed to effectively evade sanctions, trade in restricted items, and access the international banking system.

Sanctions Evasion and Illicit Procurement

Korea Tangun Trading Corporation oversees Pyongyang’s unconventional weapons-related procurement efforts, including the procurement of restricted materials. Tangun is a subsidiary of the Second Academy of Natural Sciences and was designated by the Security Council in 2009.

North Korea uses shell companies all over the world in these efforts to procure sensitive material for its nuclear program and other programs of concern. This evasion technique is regularly employed by North Korea’s shipping sector. In 2014, Pyongyang’s Ocean Maritime Management Company (OMM) was designated by the Security Council for its role in an illicit shipment of weapons from Cuba to North Korea. Prior to its designation, OMM was one of North Korea’s largest shipping companies. Since then, it has transferred control of its fleet to an elaborate network of front companies scattered around the world, and has also renamed most of its vessels in an attempt to circumvent international sanctions.

North Korea is also believed to use embedded agents in foreign companies and diplomatic personnel to trade in prohibited items. In addition, North Korean state trading companies based in China are reportedly an important channel for Pyongyang to smuggle sensitive equipment and materials. These companies are believed to operate in partnership with private Chinese companies, with many of the larger ventures operating inside of China. In recent years, a number of Taiwanese companies have also exported sensitive equipment to North Korea, including CNC machine tools, a horizontal machining center, advanced industrial computers, and stainless steel tubes.

The Chinese government’s weak enforcement of U.N. sanctions has allowed North Korea’s procurement networks to operate. According to a recent New York Times report, many of the new restrictions against North Korea, including the requirement to inspect all of its cargo, are largely ignored in the Chinese border city of Dandong, through which approximately half of China’s trade with North Korea flows. The report adds that North Korean procurement officials operate freely in the city.

North Korean banks play an important role in the evasion of sanctions, processing payments for illegal transactions and blacklisted end users. One such institution is Daedong Credit Bank, which was designated by the Security Council in 2016. Daedong held over $25 million in Macau-based Banco Delta Asia for financing North Korea’s nuclear weapons program, illicitly gained through narcotics sales and counterfeiting. Another institution is the Korea Kwangsong Banking Corporation, which was also designated by the Security Council in 2016. Kwangson has provided financial services to U.N.-sanctioned entities connected to North Korea’s unconventional weapons programs. And Pyongyang’s Foreign Trade Bank has been used to facilitate transactions on behalf of entities linked to North Korea’s proliferation network. In response to such activities, Resolution 2270 severely restricts the ability of North Korea’s banks to operate abroad. How effective these restrictions are remains to be seen.  

Proliferation to Other Countries

North Korea’s most well-known nuclear client is Syria. Until 2007, Pyongyang was helping Damascus build the Al Kibar nuclear reactor, a covert facility in Dair Alzour, which was to be used for producing plutonium. This assistance came to a halt in September of that year, when Israeli fighters destroyed the facility. Unconfirmed reports indicate that North Korea also supplied Syria with 45 tons yellowcake for Al Kibar, enough for 89 to 130 kilograms of weapons grade HEU upon further processing and enrichment. Despite the destruction of Al Kibar, Pyongyang’s nuclear assistance to Damascus may persist. Its involvement in nuclear activities in other countries is not clear.


The steady progress North Korea is making in its nuclear program is a testament to the determination of its government and the success of its illicit procurement networks. The latest round of U.N. sanctions has the potential to significantly disrupt the latter. This potential can only be realized if the sanctions are strictly enforced by U.N. member states, especially China.


* The MAEI and GBAE are sanctioned as separate entities by the UN Security Council and the US Treasury Department. Here they are treated as the same entity, per the recommendation of the UN Panel of Experts in its 2015 report.