Third Covert Enrichment Site
The US Defense Intelligence Agency’s 2017 estimate of North Korea’s fissile material stockpile — sufficient for at least 60 weapons and growing at a rate of 12 per year — was based off the assumed total highly enriched uranium output of Kangson and Yongbyon. Since the time of that estimate, The Diplomat reports that US military intelligence has detected the existence of a third covert enrichment site.
There had long been reports that the Democratic People’s Republic of Korea (DPRK, “North Korea”) had been developing a clandestine enrichment capability as part of a nuclear weapons program. An unclassified 2002 U.S. National Intelligence Estimate said that DPRK had done at least research and development for an HEU project, and subsequent unclassified intelligence reports to the U.S. Congress stated that DPRK was constructing a full-scale enrichment facility. In October 2002, North Korea admitted conducting a clandestine program to make highly enriched uranium (HEU) for weapon purposes.
In testimony to the U.S. Senate Armed Services Committee in March 2009, U.S. National Intelligence Director Dennis Blair confirmed that the U.S. intelligence community “continues to assess that North Korea has pursued a uranium enrichment capability in the past,” and added that “some in the intelligence community have increasing concerns that North Korea has an ongoing covert uranium enrichment program.”
Enrichment — “the ratio of the combined weight of the isotopes uranium-233 and uranium-235 to that of the total uranium in question” - is usually stated as a percentage. Although this definition deals with the combined weight of the two fissile uranium isotopes, in practice they are rarely mixed and are normally accounted for separately. The term ‘enrichment’ is also used in relation to an isotope separation process by which the abundance of a specified isotope in an element is increased, such as the production of enriched uranium or heavy water, or of plutonium with an increase in the fissile isotope.
An enrichment plant (or isotope separation plant) is an installation for the separation of isotopes of uranium to increase the abundance of 235U. The main isotope separation processes used in enrichment plants are gas centrifuge or gaseous diffusion processes operating with uranium hexafluoride (UF6).
The nuclear fuel cycle is a system of nuclear installations and activities interconnected by streams of nuclear material. The characteristics of the fuel cycle may vary widely from State to State, from a single reactor supplied from abroad with fuel, to a fully developed system. Such a system may consist of uranium mines and concentration (ore processing) plants, thorium concentration plants, conversion plants, enrichment (isotope separation) plants, fuel fabrication plants, reactors, spent fuel reprocessing plants and associated storage installations.
Remote detection of uranium enrichment is extremely challenging. With careful selection, placement, and maintenance, landscape elements can provide visual screening that protects sensitive operations, gathering areas, and other activities from surveillance with creating concealment for covert activity.
The IAEA, with strong U.S. support, undertook a major strengthening effort in the 1990s, in direct response to discoveries made during IAEA inspections in Iraq following the first Gulf War. These inspections uncovered an ambitious clandestine nuclear weapons program in Iraq, involving a number of undeclared installations. Of particular significance was a covert enrichment facility located adjacent to a declared nuclear facility where the Agency had been applying its safeguards for years. The IAEA had not detected this concealed activity before the war.
The Model Additional Protocol requires states to declare to the IAEA a number of nuclear and nuclear-related items, materials, and activities that, while they could be part of a peaceful nuclear program, would be required for a covert nuclear weapons program. Specifically, the Protocol requires states to report exports of nuclear-related items controlled by the Nuclear Suppliers Group, confirm imports of such items, and report domestic manufacturing of key items. It also requires states to report exports, imports, and stockpiles of raw uranium and thorium that could be used as feed material for a covert nuclear program.
The IAEA is sufficiently concerned that existing detection technologies are not adequate to address detection of covert facilities, and that the IAEA established a division specifically tasked with improving detection technology. The DOE has a similar program tasked with carrying out research and development to improve detection technology, with one effort dedicated to detecting laser enrichment.
Proliferation-prone nuclear facilities would not fail to leave traces that could be detected by the methods of environmental sampling. Uranium enrichment facilities involve thousands of processing units. The plants are physically large, difficult to start up, and difficult to reconfigure (for example, from a declared LEU plant to undeclared HEU production). Uranium stock in such a plant must be converted to UF6 gas for the process and returned to solid metal afterward. The residues are large in quantity and, because they are depleted in U-235, leave a distinctive signature.
Although remote sensing methods offer advantages for monitoring important illicit process activities, remote and stand-off technologies cannot successfully detect all important processes with the sensitivity and certainty that is desired. The main scope of the program is observables, with a primary focus on chemical signatures. A number of key process signatures elude remote or stand-off detection for a variety of reasons (e.g., heavy particulate emissions that do not propagate far enough for detection at stand-off distances, semi-volatile chemicals that do not tend to vaporize and remain in the environment near the source, etc.)
The passive millimetre-wave spectroscopy (PmmWS) technology developed at Argonne National Laboratory (ANL), in the USA, has a number of uses - including covert detection of chemical plumes. PmmWS was developed by Argonne's Nuclear Engineering Division and was primarily created to monitor chemical signatures emitted by processing facilities suspected of unauthorised nuclear activity, such as enrichment or reprocessing, and their use in weapons production. In terms of its advantages over other forms of chemical sensing, previous remote sensing instruments for terrestrial use had lower ranges of detection (from 10-l00m), were susceptible to interference from clouds and other atmospheric phenomena, and cost much more than PmmWS. The Argonne PmmWS is also more selective and can identify a particular molecule instead of just a molecular functional group.
R. Scott Kemp heads the Laboratory for Nuclear Security and Policy at the Massachusetts Institute of Technology, which aims for “peace and security through creative science.” He describes himself as a “policy physicist”. Kemp noted that "Centrifuges also produce electromagnetic emanations, both free-space radiation and artifacts induced on power lines by power supplies. The free-space signal from the centrifuge motors can be estimated by treating the motors as dipole radiators emitting at distinct frequencies in the range of 350–1,500 Hz, overlapping with wideband ultra-low-frequency emissions from geoelectric, magnetospheric, and radio-atmospheric phenomena (Habib 2007). The wavelengths of these signals imply a near-field treatment with intensity decaying as the distance cubed for distances up to a few tens of kilometers."
He also noted that "Power supply noise induced on electrical lines is a well-known phenomenon that factories such as textile plants must address to maintain line-power quality.... the energy consumption of a proliferation-scale centrifuge plant is small enough that it can be easily operated with a diesel or natural-gas backup generator, removing power lines from consideration altogether....
"In sum, there is as yet no obvious signal for long-range detection of a covert centrifuge plant."
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