Pyongyang's defiant behavior vis-à-vis Washington in pressing on with their ballistic missile tests presents a significant challenge to the Trump administration. For the time being, the regime headed by Kim Jong-un has not gone any further with their nuclear tests, possibly in order to avoid 'pushing their luck.' At the same time, North Korea continues to advance the plutonium option, which is vital to the development of their nuclear weapons, while at the same time investing massive efforts in their uranium enrichment project.
Over the last year, there has been an aggregation of indicators to the effect that North Korea had renewed its effort to produce plutonium for nuclear weapons. These indications were based on satellite imagery, including thermal images by satellites fitted with infrared sensors and capable of spotting heat-emitting installations. The images were interpreted by the experts of the 38 North website, who specialize in North Korea, of the Johns Hopkins School of Advanced International Studies.
In June 2016, IAEA estimated that Pyongyang is preparing to reactivate the plutonium-producing reactor at the Yongbyon Nuclear Scientific Research Center, about 90 kilometers to the north of Pyongyang, whose operation had been suspended since late 2015. Indeed, between October 2016 and January 2017, satellite images provided evidence to support that estimate: over the course of December 2016, the channel of the Taeryong River, used to supply water to the cooling cisterns of the reactor, was re-dredged and cleared of ice; on December 29, 2016 the images indicated that no snow had remained on the roofs of the reactor and its auxiliary buildings, owing to the high temperatures inside those buildings, contrary to the snow piled on the roofs of other nearby buildings – evidence of the preparations for the reactivation of the reactor; on January 22, 2017, a plume of water (probably hot water) was spotted over the reactor's cooling water outlet, a fact that probably indicated that the reactor was already in operation.
However, thermal images taken between September 2016 and June 2017 indicated that during said period, the plutonium reactor had been operated intermittently at a low level, or that it was not active at all. Regarding the "radiochemical laboratory", admittedly, in mid-2016 the "radiochemical laboratory" conducted a campaign where only a part of the spent fuel used in the reactor was reprocessed, but in the months of October and November 2016, heavy traffic of railroad flatcars was observed in the vicinity of the reactor, contrary to the light traffic observed during the previous months of 2016 and in 2015, and contrary to the fact that in December 2016, no more flatcar traffic was observed in the same area. This was an important finding – some of the 14-meter long flatcars carried huge casks, the likes of which had only been observed in the vicinity of the Yongbyon Nuclear Center in the year 2000, when spent nuclear fuel from the reactor had been removed and transferred to the "radiochemical laboratory" so as to separate the plutonium. Apparently, the explanation is to be found in the thermal images of September 2016 through June 2017: they suggest the possibility that the "radiochemical laboratory" had been active during that time, conducting at least two campaigns of reprocessing batches of spent fuel and extracting the plutonium it contained.
The Basis for Success – the Naivety of the West
1962 may be defined as the year when Pyongyang's nuclear program was set in motion as an outcome of the "All-Fortressization" doctrine adopted by the North-Korean regime. Although the USSR rejected Pyongyang's request for nuclear weapons, it assisted the North Koreans in the development of a "peaceful nuclear energy program". The Yongbyon Nuclear Center was established in the context of that program. It included a small, 2 megawatt research reactor (a light water model using uranium enriched to 10%), which is not suitable for the production of nuclear weapon-grade plutonium. The Center also included a radioisotope laboratory designed to produce radioisotopes for civil applications with 7 hot cells. The USSR provided reactors of this type to its allies, like Egypt and Iraq. The Yongbyon reactor was inaugurated in 1965. In 1974, its output was increased to 4 megawatt, and in the early 1980 it underwent another modernization process that included fueling with uranium enriched to 80%, and its output was increased to 8 megawatt. The program intended to produce plutonium as fissile material for nuclear weapons was launched in the 1970s. During a visit by Hans Blix, the Director General of IAEA in May 1992, North Korea admitted that its scientists had conducted, back in 1975, experiments in the separation of plutonium by radiating small amounts of natural uranium in the research reactor and extracting minute, laboratory scale amounts of plutonium from the irradiated uranium inside the hot cells of the radioisotope laboratory. The naivety of the West in the 1950s and 1960s helped North Korea in the development of its military nuclear program. Back in the 1950s, Britain developed the Magnox gas-cooled, gas-graphite decelerated reactor. The first reactor of this type, Calder Hall, was inaugurated in 1956. Originally designed to generate electrical power, it was also ideal for the production of plutonium for the British nuclear weapons. However, pursuant to the "Atoms for Peace" speech delivered by US President Eisenhower on December 8, 1953, the British Government lifted the security classification of the design and technical specifications of the Magnox reactor and they were publicized in open scientific publications. Consequently, in early 1980, North Korea started building (independently) a 25 megawatt (5 megawatt electrical) Magnox type (gas-graphite) plutonium-producing reactor at the Yongbyon center. This reactor was activated for the first time in 1986. North Korea had no trouble producing the nuclear fuel for this reactor, which included 8,000 uranium-aluminum alloy cast rods wrapped in magnesium-aluminum alloy. Moreover, in the early 1960s, Britain sold to Japan a Magnox type reactor for Japan's first nuclear power station, Tokai. Admittedly, prevailing estimates maintain that the North Korean scientists built their plutonium-producing reactor on the basis of the Magnox reactor blueprints published by the British, but it is possible that the open-source information, in itself, was not sufficiently detailed to actually implement. Accordingly, there are those who believe that in fact, North Korea obtained the detailed blueprints of the reactor of the Tokai power station through secret agents that it had planted within the Japanese nuclear community. US intelligence spotted the plutonium reactor in Yongbyon for the first time in 1982, through satellite imagery.
But the naivety of the West played into the hands of the North Koreans once again. In 1989, the Americans realized, from satellite imagery, that adjacent to the plutonium reactor the North Koreans were erecting a large, narrow building which, according to its characteristics, could be a 'hot lab' capable of separating plutonium on a large scale. As it turned out, this laboratory, which came to be known as the "radiochemical laboratory", was fairly similar to the Eurochemic irradiated nuclear fuel reprocessing facility located close to the town of Mol in Belgium, in terms of its structural characteristics and the separation technology processes used therein, like the decladding of the fuel rods and the bituminization of the liquid radioactive waste.
A Path of Deceit
Since its military nuclear program had been exposed, North Korea has repeatedly encountered crisis situations vis-à-vis the West, headed by the USA, and vis-à-vis IAEA. Pyongyang joined the NPT (Non-Proliferation Treaty) on December 12, 1985, owing to its interest in international aid that would provide some relief to their economic distress and owing to the pressure exerted by the USSR. The Comprehensive Safeguards Agreement between Pyongyang and IAEA was concluded only on January 30, 1992, and on April 9 of that year, Pyongyang ratified the NPT. At the same time, all along the way, the North Koreans misled and deceived IAEA.
In the summer of 1992, IAEA realized that the amount of plutonium actually separated in the "radiochemical laboratory" far exceeded the amount declared. During the visit by IAEA inspectors to Yongbyon in May 1992, they collected samples from the "radiochemical laboratory" and from the radioactive waste storage facility, which were subsequently tested at the IAEA laboratory in Seibersdorf, Austria and in other laboratories in Europe and the USA. The tests showed that the concentrations of the various radioisotopes in the samples had significantly exceeded the values expected according to Pyongyang's declaration. Based on these findings, IAEA estimated that in the years 1989 through 1991, the "radiochemical laboratory" had separated plutonium from spent irradiated nuclear fuel. Additionally, images provided by US satellites pointed to the locations of two additional radioactive waste storage facilities near the "radiochemical laboratory," which the authorities in Pyongyang had attempted to conceal.
The demands made by IAEA in late 1992 and in 1993 to allow their inspectors to visit those facilities and collect samples were turned down, on the pretext that the facilities were located inside a military zone. At this point, the relations between North Korea and IAEA began to deteriorate, and owing to Pyongyang's refusal to resolve the issue of the gap between its declaration regarding the amount of plutonium produced in the "radiochemical laboratory" and the findings of IAEA, the IAEA Board of Governors decided that North Korea must enable IAEA to conduct special inspections at the suspected facilities. The deadline set for compliance was March 25, 1993. In response, the North Koreans announced, on March 12, their withdrawal from NPT. They soon realized the severity of the consequences of their hasty move, however, and in early June, before their withdrawal had become effective, they backed down.
1994 was a year of upheavals. In April, Pyongyang announced that they had stopped the operation of the plutonium reactor in order to refuel the core with fresh nuclear fuel. The American intelligence community, on the other hand, believed that the discharging and refueling process of the reactor in 1994 had been preceded by a previous discharging and refueling process in 1989, which was not reported to IAEA. Les Aspin, US Secretary of Defense at the time, said as much on December 7, 1993.
This assumption is consistent with the estimates of IAEA that in the years 1989-1991, the "radiochemical laboratory" had carried out plutonium separation operations. The amount of military-grade plutonium produced at the reactor in line with the scenario according to which the reactor had been discharged and refueled in 1989 as well, should be higher than the amount in line with the scenario according to which the process was carried out for the first time in 1994. Eventually, through the mediation of former US President Jimmy Carter, North Korea pledged, in August, to freeze the military nuclear program and dismantle the plutonium production infrastructure it had erected as an "agreed framework" signed jointly with the USA.
In exchange, North Korea should have received assistance for the development of its energy economy, including the establishment of two large LWR (Light Water Reactor) type electricity generation reactors, as well as the supply of 500,000 metric tons of heavy fuel oil per year for heating and generation of electrical power until the first LWR type reactor has become operational. For this purpose, KEDO (the Korean Peninsula Energy Development Organization) was established in 1995. Indeed, once North Korea finalized the agreed framework with the USA in 1994, Pyongyang deactivated the plutonium reactor and the "radiochemical laboratory." However, much uncertainty still remained regarding the amount of plutonium produced at the plutonium reactor in the years 1986-1994 and subsequently separated in the "radiochemical laboratory." But the North Korean zigzagging continued. That was not the conclusion of North Korea's activity in the plutonium path: pursuant to their final withdrawal from the NPT in 2003, they reactivated the plutonium reactor and the "radiochemical laboratory."
According to an estimate made in late 2007 – the time when the reactor was deactivated once again, as a confidence-building move vis-à-vis the USA – the amount of plutonium North Korea had produced, considering the uncertainty of the data, came to 40 to 50 kilograms of military-grade plutonium. This amount is sufficient in order to build 6 to 8 nuclear weapons, assuming the plutonium reactor produced, during each one of the years while it was active, about 6 kilograms of plutonium, the amount required in order to build one nuclear weapon, and that all of the plutonium had been extracted from the spent irradiated fuel in the "radiochemical laboratory."
Between October 31 and November 4, 2006, a delegation of American scientists from Stanford University visited the Yongbyon Nuclear Scientific Research Center in North Korea. The delegation included Professor Siegfried Hecker, formerly the Head of the Los Alamos National Laboratory, the US nuclear center where, during World War II, the first American atomic bomb had been developed. Professor Hecker had devoted his career to the development of US nuclear weapons. Between 2004 and 2015, Professor Hecker visited North Korea seven times. During his visits in 2004, 2006, 2008 and 2010 he was invited to visit the Yongbyon Nuclear Center, in an unofficial capacity.
Pyongyang used Professor Hecker as a conduit for conveying information to Washington regarding the status of their nuclear program, while the US government officials regarded this as a convenient arrangement for extracting inside information from within the fortified walls of North Korea. During the visit of the American delegation in 2006, they were accompanied by the Director of the Yongbyon Center, Dr. Ri Hong-Sop. When Dr. Ri presented the 25 MW reactor and the "radiochemical laboratory" to the visiting delegation, he stated with pride that his people had mastered the technology of the plutonium production cycle. According to him, one primary improvement in the plutonium extraction process in the "radiochemical laboratory" involved the replacement of some of the mixer-settler systems in the pulsed columns. Referring to the Yongbyon nuclear fuel production facility, Dr. Ri stated that his people were completing the preparations for the establishment and refurbishment of the facility, and that it was expected to be reactivated in 2007.
Regarding the third reactor (200 MW) erected at Yongbyon and the large reactor (600-800 MW) erected in Taechon, construction was discontinued pursuant to the "agreed framework" of 1994. Admittedly, during Professor Hecker's visit to Yongbyon in 2006, Dr. Ri informed him that a final decision regarding the fate of those two reactors was yet to be made, but in November 2010, Professor Hecker made his fourth visit to the Yongbyon Nuclear Center, at the head of a delegation of 3 scientists from Stanford University. The North Korean liaison to the delegation, a senior technical official, confirmed that pursuant to the agreement with the USA in 1994, the authorities in Pyongyang demolished the two large gas-graphite reactors that were under construction at the time and they "have become ruined concrete structures and iron scrap." According to this official, in place of those reactors, Pyongyang opted for a new beginning, and since July 2010 the North Koreans were independently building an LWR type experimental reactor having an estimated output of 25-30 MW electrical, with the intention of building an LWR reactor based electricity generation infrastructure in the future. The North Korean official added that his country's nuclear program also included the development of the fuel cycle for these reactors, including the uranium enrichment capability required for this purpose. Subsequently, the North Korean hosts even presented the construction site of the experimental LWR reactor to their guests.
In June 2008, as a gesture of its willingness to abandon its military nuclear program, North Korea demolished the most prominent symbol of its plutonium project – the 18-meter high cooling tower of the reactor. In April 2009, however, the pendulum changed direction once again: the failed launching of a satellite into space by North Korea, despite international pressures that had attempted to prevent it from attempting the launch, appeared to the international community as a cover-up for a technology-testing experiment for an Intercontinental Ballistic Missile (ICBM). Accordingly, North Korea was condemned by the UN Security Council, and the sanctions imposed on it were expanded. Pyongyang responded promptly by conducting a nuclear test in May 2009 and by reactivating the "radiochemical laboratory."
North Korea's defiant conduct vis-à-vis the West grew even more extreme owing to the third nuclear test it conducted in February 2013, and the declaration in April of its intention to refurbish the reactor in preparation for the reactivation thereof. Satellite images indicated that the reactor was, indeed, reactivated at that time, but that must have been a sporadic operation, owing to the obsolescence of the infrastructure and the malfunctions encountered in the new cooling system installed therein. Additionally, by December 2013, it became evident that a new nuclear fuel production plant had been erected at Yongbyon – for the plutonium reactor and the experimental LWR reactor that was under construction.
North Korea's Nuclear Weapon Status
Opacity and uncertainty still shroud the amount of nuclear weapons actually available to Pyongyang. According to the estimate of Professor Hecker in late 2016, the amount of fissile material, plutonium or military-grade highly enriched uranium (HEU) Pyongyang was expected to have by the end of 2016 is sufficient for the manufacture of some 20 nuclear weapons. The estimate of David Albright, Head of the esteemed Washington-based Institute for Science & International Security (ISIS) at that time was somewhat different – between 13 and 30 plutonium and HEU weapons, subject to the uncertainty as to whether North Korea currently operates one uranium enrichment facility or two. David Albright also estimated that North Korea was expanding its nuclear weapon arsenal at the rate of 3-5 weapons per year.
North Korea has thus far carried out five nuclear tests. The first was conducted on October 9, 2006, at the Punggye-ri underground testing facility, located in a mountainous area of the Kilju Province in the north-eastern part of the country, where all of the following tests were conducted as well. The West regarded that test as a "fizzle" as the yield of the blast, according to the noise level measured by the seismic station in South Korea, was between 0.5-1.0 kilotons. Conversely, according to Pyongyang, the yield was four kilotons.
On the other hand, the radioactive debris released into the atmosphere pointed to the detonation of a nuclear explosive device with a plutonium core. The second test (May 25, 2009), which also involved a plutonium core, was more successful, with a yield estimated at 2 to 5 kilotons. The prevailing estimate regarding the yield of the third test, conducted on February 12, 2013, was 6 to 9 kilotons. However, the announcement by the news agency of Pyongyang claimed that the test reflected a high degree of sophistication in the development process, as the explosive device was miniaturized. Regarding the type of core of the nuclear device, it is estimated that unlike the previous tests, it had a uranium core – but there is no evidence to support this estimate.
Satellite images from December 2015 spotted the excavation of a new testing tunnel at the Punggye-ri facility – an indication of North Korea's intention to conduct the fourth test, which was actually conducted on January 6, 2016. According to Pyongyang, this test involved a hydrogen (thermonuclear) device, but the international media doubted that. In any case, experts worldwide assume that the test may have been intended to involve a hydrogen device, but that it partially failed. Alternately, there are those who believe that the test was conducted with a nuclear explosive device of uranium or plutonium, boosted with hydrogen material.
However, the possibility that North Korea is developing a thermonuclear weapon capability is supported by a current report by the Washington-based Institute for Science & International Security (ISIS), according to which a lithium-6 production facility had apparently been erected near the town of Hungnam, on the eastern coast of North Korea. This estimate is based on North Korean efforts to acquire equipment and materials in 2012, which were probably unveiled through monitoring of the communication between the North Koreans and their overseas suppliers. Lithium-6 is a stable isotope, naturally occurring with an abundance of 7.5% in the metal lithium. It is separated from lithium-7, the most common isotope, through a chemical enrichment process. It serves as an explosive in thermonuclear weapons, or as a booster of the yield of nuclear bombs.
The fifth and most recent nuclear test by North Korea (September 9, 2016) was the most substantial by far, producing a yield of 20 to 30 kilotons. Admittedly, according to the Japanese newspaper Asahi Shimbun of June 11, North Korea was, at the time, on the verge of a sixth nuclear test, according to "intensive activity" identified at the Punggye-ri facility, but according to the 38 North website, based on satellite imagery, no irregular activity was spotted at the testing facility during that time, although the experts of that website maintained that "as long as the site remains in standby status, a sixth nuclear test could be conducted at any time with minimal advance warning. At this point, renewed nuclear testing is almost entirely dependent on a North Korean leadership decision."
Tranquility has never lasted long in the Korean Peninsula. For now, a question mark hangs over the explosive situation in this region.
Lt. Col. (res.) Dr. Rafael Ofek is an expert in the physics and technology of nuclear power. He had served in the Israeli intelligence community as a senior researcher and analyst.