Integrated Field Exercise 2008 concludes successfully

To provide the exercise with a realistic setting for a possible violation of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), the fictitious State of Arcania was invented. A seismic event of magnitude 4 accompanied by an inexplicable release of the radioactive substance Cesium 137 created the necessary backdrop.  They could both have been caused by an underground nuclear explosion. International experts as well as CTBTO staff participated in the exercise, playing the roles of the CTBTO inspection team and representatives of Arcania.

The initial inspection period had ended on 12 September with no clear signs of a recent nuclear explosion.  Inspection techniques such as visual observation, radiation monitoring, environmental sampling and seismic aftershock monitoring had been used. These techniques had enabled the inspection team to single out several areas that triggered their increased interest. Accordingly, the team requested for a continuation of the inspection.

As foreseen by the Treaty, more intrusive techniques can be used during the second phase of the inspection, the so-called continuation period. Inspectors apply geophysical methods to find features of potential underground nuclear explosions that are not visible from the surface. “We are trying to use physics to see infrastructure or a cavity below the surface that may be evidence of an underground nuclear explosion,” said Matthew Purss, geophysicist and inspector in the exercise.

Geophysical techniques are time consuming and cover very limited areas. This is where the integration of inspection techniques assumes special importance. “We work in synergy with the other sub-teams of the inspection team: visual observation, seismic aftershock monitoring and radiation monitoring. Their findings help us to narrow down the search area,” explained Purss.

The techniques applied during the exercise’s second phase included ground penetrating radar for the examination of the shallow subsurface layers down to about five metres.  Magnetometry was also used during this phase. This entails  measuring the Earth’s magnetic field and  can be used to detect anomalies.  During the exercise this technique was applied in two variants: ground-based with hand-held magnetometers, and air-borne with a so-called mag bird tied to a helicopter.

In order to survey the deeper layers several hundred metres below the Earth’s surface, inspectors used various electrical conductivity techniques. A set of electrodes were used to inject an electrical current into the ground for depths of up to one hundred metres.  The responding signal was then measured by another set of electrodes. For depths of 500 metres and more, inspectors used artificially generated electro-magnetic fields to search for anomalies in the ground.

The inspectors did not find any evidence of a recent nuclear explosion. However, the application of geophysical techniques showed the effects of previous nuclear explosions that had been conducted at the site between 1949 and 1989.  Geophysicist George Tuckwell, another member of the exercise inspection team, said that they could identify changes in the subsurface caused by previous underground nuclear explosions: “The physical properties of the ground are changed, as we could see for instance in the ground water systems.”

For the first time in a field experiment, the inspection team conducted sub-soil air sampling to detect traces of the radioactive noble gas Argon 37. Unlike the noble gas Xenon, Argon 37 is not a direct product of a nuclear explosion. Matjaž Prah, the inspection’s sub-team leader for radionuclide techniques, explained that it would be created through the interaction of a nuclear explosion with the surrounding rock: "Argon 37 is not a natural radionuclide. It only appears when neutrons hit calcium. This is really something like a smoking gun."

The last field trips had now been completed.  With temperatures having plummeted once again, inspectors huddled in their tents to prepare the first report, the Preliminary Findings Document.  Information gathered during the exercise did not support the assumption that Arcania had conducted an underground nuclear explosion.  All the usual tell-tale signs were absent, including the occurrence of relevant radioactive substances.

With the last signature on paper, the inspection simulation ended.  The fictitious State of Arcania ceased to exist. It had served the purpose of putting the CTBTO on-site inspection regime to a stringent test under realistic and challenging conditions. The simulation included role-playing in order to provide a realistic setting for the exercise.  Participants had to work with the assumption that they were at a real inspection.  The inspected State Party team was headed by John Walker, a disarmament expert from the United Kingdom. Walker’s team created several challenges for the inspection team.  “It is important to provide a very difficult task for the inspectors to react to, to test them, so we can test the procedures and learn lessons on how to improve the manual and the SOPs (Standard Operating Procedures),” Walker explained.

The key phrase now is ‘lessons learned’.  An exercise of this magnitude is bound to result in a long list of issues that need to be revisited when discussing guidelines for on-site inspections.  “It is now time to take stock,” said inspection team leader Wang. “This exercise will take us a long way on issues such as techniques, equipment and procedure,” he added. Wang’s assessment was shared by the CTBTO evaluators who believe that their exercise observations will stretch over several hundred pages. During the entire duration of the exercise, evaluators observed activities in the field and in the base of operations.  They conducted interviews with participants in the various functions and carried out a thorough survey.  Asked about the evaluators’ mandate, the evaluation team leader Paul Stokes said: “We observed the entire operation to see how well it went and where the gaps were.”  CTBTO evaluator Javier Guarnizo added: “We provide feedback on the readiness of the on-site inspection regime on all levels: technical, managerial and logistical.”