North Korean state news agency KCNA announced at the end of April that after six nuclear tests, North Korea had met its objectives and would no longer be needing the Punggye-ri nuclear test site.
Dismantlement of the site started almost immediately even earlier than officially announced. OnMay 2 the U.S. intelligence community observed that cabling was removed from the site which is critical for obtaining diagnostic information for analysis of a nuclear test. OnMay 7 my colleagues at the Middlebury Institute of International Studies at Monterey noticed that a heavy truck was present at the South portal that may have removed technical equipment from the test site.
Should the testing program be reinstated, such equipment could undoubtedly be used again. In addition, both my colleagues and researchers at38 North noticed that significant changes at the test site were occurring : site buildings were razed and rail tracks removed.
The spectacle was reminiscent of the cooling tower demolition at the Yongbyon nuclear complex in June 2008 widely heralded by the media but considered to be more skeptical to experts.
It is impossible to verify whether explosions occurred only at the tunnel portals or occurred throughout the tunnel complex
Savvy journalists tried to bring dosimeters to verify the dose at the site, but these were confiscated at the airport leading to suspicion by many on the legitimacy of the destruction of the site.
At the “closure ceremony” journalists were showna map of the location of explosives throughout the tunnels. However, it is impossible to verify whether explosions occurred only at the tunnel portals or occurred throughout the tunnel complex since bona-fide experts were not invited with the right equipment and access.
The lack of transparency raises doubt over whether the closure ceremony is legitimate, or whether it hedges future use of the complex should North Korea deem it necessary.Five states (France, South Africa, Russia/Kazakhstan, United States and United Kingdom) claim to have dismantled their nuclear weapon sites. Only Kazakhstan allowed on-site monitoring by outside observers to verify the closure of the site in collaboration with local experts. We should not be surprised that North Korea takes a cautious approach.
There is much to be revealed about the nuclear weapon design that could be considered sensitive. Efforts must have been by made by North Korea to prevent disclosing sensitive information: undoubtedly why North Korea was concerned about journalists carrying dosimeters and why they did not invite experts – though I would argue that little information related to nuclear weapon design could be learned with a simple dosimeter.
Samples taken from the site could reveal the type of fuel used in the test device, whether it was enhanced with tritium gas (known as boosted devices) or whether it was fusion or fission energy dominated.
It is widely surmised that the last nuclear test had an appreciable fusion energy component based on the fact that the energy released was at least a dozen times more than the energy released by the bombs dropped on Hiroshima and Nagasaki. However, the design of the bomb is unknown.
Hundreds of distinct isotopes are produced when a nuclear device detonates. The relative proportion of these isotopes will be sensitive to the type of fission fuel as well as whether some of the energy released is due to fusion. In addition, neutrons steaming from the nuclear explosive device can react with bomb materials and surrounding rock to produce radioactive isotopes. These isotopes can be detected by taking samples nearby to where the test occurred.
Another tell-tale sign of fusion-based nuclear explosives is the presence of unusual isotopes which are produced when multiple high energy neutrons bombard bomb materials that successively absorb neutrons. Inspectors may even find debris of test objects in the tunnels used to detect the effect of electromagnetic pulse effects or other nuclear weapons effects, or find materials used to gauge the size of the explosion.
Samples taken from the site could reveal the type of fuel used in the test device
Information learned from these on-site inspections along with full disclosure of documentation by North Korea will be critical for getting a complete picture on the extent of the nuclear weapons complex.
A full accounting of the amount of fissile material used in the nuclear tests based on inspections and documentation disclosed to the inspectors will be necessary to verify the total amount of remaining fissile material. The job of the International Atomic Energy Agency then will be to integrate all the information obtained and verify that the production of fissile materials in various facilities meets with their expectations. If a discrepancy is evident, it may be because of the existence of a clandestine facility. Crucial to a full accounting will also be full knowledge of how much fissile material was actually used in the various tests which is sensitive information since it is related to the type of nuclear devices detonated.
All is not lost, even though the tunnels or maybe just the portals have been destroyed, independent experts will still be able to access samples by drilling back into the site. These samples will still reveal relevant information for verifying the North Korean nuclear program.
In areport aired last week on CNN, some United States intelligence officials raised suspicions that the site demolition was not legitimate.
However, there are serious logical flaws in the report. First, the report suggested that the dust cloud produced could be used as a gauge to determine the size of the explosives used in the tunnel complex and the size of the cloud inconsistent with destruction of the entire tunnel.
It is obvious that dust evolution from the portal entrance could only be a measure of the size of explosion at the entrance and is not an indicator of the size of the explosion throughout the tunnel complex.
Furthermore, the report stated that the size of the explosion as measured by seismic sensors was not very high. It is unlikely that the United States has technical resources that have precise enough seismic sensors that can detect small subterranean explosions.
This is especially true since the explosions were likely triggered at different times and locations rather than one large explosion. The United States utilizes a low profile intelligence agency known as theAir Force Technical Applications Center (AFTAC) to monitor nuclear explosions which operate a clandestine seismic network. The closest location for these sensors would be in the Demilitarized Zone: too far away to detect small conventional explosions with any precision.
Independent experts will still be able to access samples by drilling back into the site
China has stations nearby, but it is unlikely that they share data with the United States. Considering that the explosives on the map provided by NK officials to the journalists were set far enough from the location where the nuclear tests were conducted the explosions would not have triggered further collapse of the enormous cavities produced by the previous nuclear test explosions.
This is likely the source of unusual seismic activity after the latest nuclear test that would have been detected by outside observers. In sum, we only know that the tunnel portals have collapsed but this is far from irreversible since we have no data on the size of the explosions throughout the tunnel or whether these occurred.
As pointed out byTariq Rauf, former Head of Verification and Security Policy Coordination at the International Atomic Energy Agency (IAEA), almost all closures of nuclear test sites (except for Kazakhstan) were conducted by the states themselves. North Korea is the only country that can safely and securely dismantle Punggye-ri nuclear test site. This wasechoed by Dr. Siegfried Hecker, former Director of Los Alamos National Laboratory and well known expert on North Korea’s nuclear weapon program.
However, the proper way to do dismantlement and prevent access in the interest of public safety and nonproliferation is to stem the entrance of the tunnels with reinforced concrete making it more laborious to enter the site, as was done at the Kazakhstan Semipalatinsk nuclear test site. This has not been done yet in the case of Punggye-ri.
It is critical to realize that a team of international experts are always on call if requested by a member state to verify that a seismic event was actually a nuclear explosion.
These are experts from the preparatory commission of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) that monitor the globe 24/7. The CTBTO operates the International Monitoring System with a network of hundreds of seismic sensors and experts who have been trained in how to conduct on-site inspections of nuclear test sites. They would be ideal independent experts to verify to the international community if the test site was successfully dismantled.
While many media outlets reported that the statement implies that North Korea would send international inspectors to the closure ceremony which regrettably did not happen. There is room in an alternative interpretation of that statement to imply that inspectors could still be sent.
North Korea, experts are still waiting (yours truly tried to go but alas was not successful) and will go ina weeks’ notice if requested.
Edited by Oliver Hotham
Featured image: KCNA
North Korean state news agency KCNA announced at the end of April that after six nuclear tests, North Korea had met its objectives and would no longer be needing the Punggye-ri nuclear test site.Dismantlement of the site started almost immediately even earlier than officially announced. On May 2 the U.S. intelligence community observed that cabling was removed from the site which is critical
Dr. Ferenc Dalnoki-Veress is Scientist-in-Residence at the James Martin Center for Nonproliferation Studies and holds an MSc and PhD in high energy physics from Carleton University, Canada, specializing in ultra-low radioactivity background detectors and has professional experience in the field of astroparticle physics, primarily neutrino physics.