CTBTO on-site inspection simulation
completes first phase
It is now more than a week into the integrated on-site inspection (OSI) field exercise conducted by the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) and the first phase of an OSI in the fictitious State of Arcania has been completed. The CTBTO inspection team handed over its progress inspection report to the Director General after review by the inspected State Party on 12 September, which indicated that the inspection techniques used during this initial period did not bring to light any evidence of a recently conducted nuclear explosion. The team did, however, identify a number of areas of interest that required further study using advanced methods.
Consequently, the inspection team proposed that the inspection be continued into the second phase – the so-called continuation period – when an additional number of techniques, mostly geophysical methods, would be used. The inspection techniques which had been employed previously, including seismic aftershock monitoring, gamma radiation monitoring and visual observation, would continue during the second phase, complementing the geophysical inspection techniques.
Settling into the daily routine
Over the last ten days, the small tent town just outside the confines of the former Soviet Union nuclear test site has settled into a daily routine. The 180 experts from all over the world have become accustomed to play their part in this simulation of an on-site inspection in the fictitious State of Arcania. In the scenario for this exercise, the CTBTO registered an event on the territory of Arcania which – according to relevant analysis – may have been a nuclear explosion, thus triggering an OSI, the ultimate verification measure of a global alarm system being built by the CTBTO to detect nuclear explosions.
The extreme weather at the start of the OSI simulation was a test in itself, forcing the inspection team to be flexible and inventive in the implementation of their mandate. After the weather improved, inspection activities returned to full swing and inspectors started every morning with routine preparations for their field trips.
A fleet of seven or eight Russian UAZ vans waited every morning to take inspectors out to the plains of the Kazakh steppe. As there are very few roads and tracks in the former Soviet Union nuclear test area —or Polygon, as it is called here — the vans crisscrossed the grassland relying on electronic guidance by GPS.
Clearly defined inspection techniques
Inspectors went out every day to implement inspection techniques defined by the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and detailed in the OSI operational manual. During the initial period of the inspections they performed visual observation, seismic aftershock measurements and gamma radiation monitoring.
Getting an overview of the inspection area
Visual observation is crucial at the beginning of an OSI. It helps inspectors to get oriented. But the main purpose of this activity is to identify anomalies in the inspection area that may need further investigation. As the Arcanian weather prevented the helicopter from taking off during the first couple of days, the inspection team had to resort to the Russian UAZ vans for their first overview of the inspection area.
Different kinds of equipment can be used during visual observation such as still cameras, video cameras and binoculars. However, Bernd Ludwig of the German Bundeswehr Verification Centre in Geilenkirchen, who headed the visual observation sub-team pointed out that: “Our main instruments are our eyes and of course our training, which enables us to identify those phenomena that we are looking for."
Surveying the terrain from the air
The initial overflight is guaranteed by the Treaty and cannot be refused by the inspected State Party. The overflight was divided into two parts for practical purposes. Prior to each take-off, the inspection team agreed on the line pattern covering the inspection area that would be used for the flights. In keeping with the scenario, the inspected State Party put up some obstacles such as no-fly zones and areas of restricted access, forcing the inspection team to negotiate their way around these areas.
During the overflight, the inspection team identified some areas that attracted their interest and might require more investigation. Accordingly, they planned some of their visual observation tours on the ground to have a closer look at these areas. “Everybody can understand that you can distinguish some general features from the air, but in order to see the details you need the ground-based visual observation,” said Ludwig.
Hundreds of photographs taken
The visual surveys of the area resulted in over 400 photos, which had to be coordinated with maps and landmark features memorized by the inspectors. The outcome was then reviewed regularly by both the inspection team and the inspected State Party and served to identify the next steps. Maintaining the scenario’s realistic atmosphere, the inspected State Party insisted on removing an occasional photograph from the central log when it considered it as either irrelevant to the purposes of the inspection or as violating Arcania’s national security interests.
Although visual observation is considered of crucial importance at the beginning of an exercise, it would continue throughout the exercise. While the inspection team applied a range of other inspection techniques, findings acquired during these activities may call for additional tours by inspectors to have a closer look at specific features in the inspection area.
Seismic network deployed to detect possible aftershocks
Among the first activities during an inspection is the deployment of a seismic network throughout the inspection area to record possible seismic aftershocks. Following a nuclear explosion or an earthquake, geological structures in the vicinity that were disturbed by the event will settle, causing minute seismic events with distinct seismic signatures. As the number and magnitude of seismic aftershocks would decrease rapidly after a possible nuclear explosion, the deployment of seismic monitoring equipment has to be carried out immediately upon arrival of the team in the inspection area.
Peter Labak, an expert from Slovakia who is leading the seismic sub-team, said that an initial 27 mini-arrays and two 3-component stations were deployed to cover most of the inspection area. Information from this network helps the inspectors to search for the area where the triggering event may have taken place and to identify the nature of the event.
After approximately ten days the seismic team had not recorded any aftershocks pointing to a nuclear explosion. Despite the absence of relevant data, the team decided to move on to the next phase. “We are now intensifying the network by three additional 3-component stations which will be placed near the no-access zones,” said Labak. “We had no visual or physical access to this area and want to find out what is going on there.”
Searching for unusual gamma radiation
Over the last few days of the inspection, the inspection team has also performed gamma radiation surveys to detect areas with elevated radiation levels which may point to the possible release of radionuclides from a nuclear explosion. These surveys were conducted by air from a helicopter and on the ground using car-mounted measuring equipment. Since the severe weather during the first few days of the inspection had prevented the helicopter from taking off, no airborne gamma radiation surveys were conducted at first and surveys using vehicle-mounted equipment were intensified.
Matjaz Prah, an expert from the Croatian State Office for Nuclear Safety, supervised the gamma radiation survey activities. He said that the inspection team could only look for traces of radionuclide particles and noble gases that are relevant for the inspection. Asked what the inspectors would do when finding areas with elevated gamma radiation levels, Prah replied: “First we perform a thorough investigation using hand-held gamma detectors and if there is really something relevant for an inspection we need to send sampling teams.” These samples would then be thoroughly investigated in a radionuclide laboratory to check for relevant radioisotopes.
Environmental sampling itself is a very tedious and minutely described procedure. Previous exercises have helped refine procedures on how to collect various types of samples such as vegetation, soil, water or air. Last year’s exercise in Chernobyl, Ukraine, focused on radiation measurements and environmental sampling.
Malcolm Cooper, a radiation monitoring and safety expert from Australia, participated in the exercise in Ukraine: “Chernobyl was the first exercise where we had put the whole process together – the sampling in the field, the bringing back to the lab and the chain of custody and we have refined all these procedures,” he said. “Now we can see what really works and what doesn’t and we can see where procedures can be further improved.” Procedures need to be consistent and the chain of custody needs to be ensured.
Health and safety come first
During all inspection activities, the health and safety of the inspectors were of the highest priority as the exercise took place at a former nuclear test site and the risk of contamination by radioactive substances was real. Cooper stated that contamination levels are generally low but not evenly distributed across the area, which: “… makes it difficult for inspectors and they have to be careful wherever they go because we don’t know the full distribution pattern.”
In preparation for this exercise, the risk of radiation exposure was calculated on the basis of recently gathered data in the inspection area by the Kazakh authorities. Malcolm Cooper explained that the exposure to radiation might be comparable to high altitude long distance flights: “The maximum dose rate that we might encounter would be comparable to me flying from Melbourne to Vienna and back just being exposed to normal cosmic radiation.”
Stringent measures to protect against radiation contamination
Every day a set of measures was taken to protect all participants in the exercise against unwanted radiation exposure. No one was allowed to remain in the inspection area for more than six hours on each given day, thus keeping the potential exposure to an acceptable minimum. Everybody who went on a field trip – be it inspector, observer or evaluator – had to wear protective overalls, overshoes and a face mask.
Upon returning from the field, everybody would undergo decontamination procedures to make sure that there were no contaminants on their clothes, faces or hands. If any contamination were found they had to take measures to remove them before entering the base of operations. These measures were adhered to meticulously in order to prevent transferring contaminants from the inspection area into the base of operations.
In addition, all participants in the exercise were equipped with dosimeters— a radiation monitoring device that determines how much radiation they received during the entire stay. Anyone who entered the inspection area carried an additional radiation monitor that would display the radiation dose in real time and sound an alarm if acceptable levels were exceeded, allowing the wearer to remove himself from the source of the radiation immediately.
All inspection activities serve to acquire information that may help determine whether or not a nuclear explosion had been conducted. The results from the different measurements help narrow down the inspection area to smaller areas that would need to be investigated closer with the help of other inspection techniques.
The experts agree that inspection techniques are complementary and do not function in isolation. Results from one technique may lead to intensifying the investigation of certain areas or phenomena in the inspection using different techniques. Visual observation may lead to intensified gamma radiation measurements in the observed areas.
Even the usual radiation checks in the field that are actually part of the health and safety procedures may indicate the need to carry out additional gamma radiation measurements to identify observed elevated radiation levels. Also, elevated gamma radiation levels registered while using air-borne instruments can initiate additional visual observation trips into the inspection area.