Howard Hall, UT-ORNL Governor’s Chair for Global Nuclear Security and director of the Institute for Nuclear Security, poses with model train that is used in his research to develop a means of detecting the location of a moving source of radiation.
Professor Howard Hall is an expert in nuclear security, with recognition from the US Department of Homeland Security and the National Science Foundation. He serves as the director of UT’s Institute for Nuclear Security.
He has delivered talks and held seminars around the world on nuclear proliferation, security, and detection, and has worked extensively with Oak Ridge National Laboratory (ORNL) and the Lawrence Livermore National Laboratory.
Hall, the joint UT-ORNL Governor’s Chair for Global Nuclear Security, addressed some of the topics being raised in light of the recent summit between the United States and North Korea.
What is the first step for a country when it de-nuclearizes?
Hall: The key will be what the term denuclearize means in the context of the agreement. If expressed broadly, it would presumably include elimination of existing nuclear weapons, demilitarization of delivery systems, elimination of programs and facilities that enable the development of both weapons and delivery systems—research labs, test sites, enrichment and reprocessing facilities—and redirecting human expertise to other purposes.
I doubt the agreement will be that broad, because some, if not many, of the capabilities that underlie a national nuclear weapons program are dual use. For example, a radiochemistry capability can help you analyze special nuclear material or post-detonation materials to diagnose weapons performance but also can help produce medical isotopes and therapeutic agents. So step one is defining an end goal along with confidence-building measures along the way.
If we presume that denuclearization encompasses elimination of weapons but retention of peaceful uses of nuclear technology, the first step is a declaration of what facilities are which. Then there will have to be a monitorable and verifiable plan to dismantle or disable them.
Is there a way to tell how the process is going without actually visiting the sites?
Hall: In some cases, overhead imagery might allow confirmation, but I think this is unlikely in North Korea. I think observers with boots on the ground will be necessary and critical to the credibility of any denuclearization process.
How can you monitor or tell whether they resume production at a later date?
Hall: Continued access and site visits. North Korea will have to become quite a bit more open, especially if the deal permits them to retain peaceful use applications—which can potentially include enrichment.
What happens to the materials that the country has already produced?
Hall: They need to be secured, demilitarized, and properly disposed of. The pathway for these processes are not necessarily simple—who will do it? How will it be done? Where will the demilitarized materials go? The United States’ mixed oxide fuel plant effort is a good case study in how hard it can be in an open and litigious society like ours. North Korea has fewer internal obstacles to the will of the government, so it should be faster.
Ultimate disposition could include deep geologic disposal in North Korea, conversion to civilian fuels and use, transfer to a third party, or some variant of all. The US-Russia Megatons to Megawatts program, in which we bought Russian weapons-grade materials that the Russians downblended to reactor fuel, could be a great precedent.
How long does it take to eliminate each nuclear weapon, and what is that process like?
Hall: Not knowing the specifics of North Korean weapons designs, I can speak only in generalities. Each nuclear weapon has, at a minimum:
- Some sort of outer structure or cover (the part that connects to an aircraft, missile, or other delivery system to make it readily handled by troops);
- An arming, fusing, and firing system that starts the high explosive detonation when the weapon is at the point you want it to explode (and hopefully fail-safes that prevent inadvertent detonation);
- High explosives arranged around the nuclear fuel to initiate a rapid supercriticality; and
- Some mass of nuclear fuel—most likely plutonium-239—or possibly highly enriched uranium.
Dismantlement is basically the controlled, cautious reversal of the assembly process. In our systems, we take extraordinary care to make sure everything is safe before assembling or disassembling nuclear weapons. I suspect North Korea may not have met US safety standards, so part of the question is how those risks will be handled and how the process will be verified.
Actual hands-on work to separate the fissile materials from the explosives probably takes a few days to a few weeks per weapon. Getting to the point of putting wrenches on bolts will take a lot longer if it’s done to US standards.
How soon can former nuclear sites be cleaned for other uses?
Hall: This will really depend on the level of contamination and how it is dispersed. Separating plutonium from irradiated reactor fuel makes a lot of nasty waste—see, for example, Hanford in the US or Lake Karachay in Russia.
Depending on how careful North Korea was with waste handling and disposal, it may well be that some sites will have to be off limits to general access for the foreseeable future. If they disposed of waste in underground burials or tunnels, it may be possible to just seal them off and monitor the groundwater. North Korea has a lot of granite in its geology, so depending on the groundwater chemistry, many of the most unpleasant isotopes won’t migrate quickly.