CTBTO conducts field exercise in Chernobyl

A small herd of wild horses gallops across the grassland, fleeing from the loud noise of the Mi-8 helicopter flying above. A moment later the helicopter has the same effect on grazing elk. What appears to be a national reserve is the Chernobyl* exclusion zone in the Ukraine. The area has been largely abandoned by its former human inhabitants and is now teeming with wildlife. It's June 2007 and the helicopter carries a group of experts who are in the midst of an on-site inspection exercise organized by the Preparatory Commission for the Comprehensive Nuclear Test-Ban-Treaty Organization (CTBTO). The CTBTO is mandated to develop the tools needed to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) once it enters into force. These tools, integrated in the CTBT verification regime, will ensure that no nuclear explosion goes unnoticed. On-site inspections are an essential part of the verification regime and represent the ultimate means to verify whether or not a nuclear explosion has occurred. Experts at the CTBTO develop methods and procedures to establish how best to go about such an on-site inspection.

Theory has to be tested in practice. Project manager Gregor Malich of the On-Site Inspection Division (OSI) of the CTBTO, along with a group of 36 experts from 21 countries and the CTBTO, did just that. "We wanted to bring together experts and equipment and let the experts apply methods and procedures for the implementation of Treaty-approved techniques in a realistic environment", he said. A number of different techniques are applied during an on-site inspection. The exercise in the Ukraine focused on measuring radioactivity and identifying the relevant elements causing that radioactivity. The aim of the exercise was to determine best practices and operational requirements, including related logistics and infrastructure.

The headquarters of the exercise was located in Chernobyl, about 90 km north of the Ukraine's capital, Kiev. Today, 21 years after the accident in the nuclear power plant, located 15 km further to the north, Chernobyl is like a ghost town. Formerly inhabited by 50,000 people, the town is now seemingly empty and incredibly green, its streets reclaimed by nature. Turning into any side street, one could make the mistake of thinking oneself out in the wilderness. But the houses behind the lush green, albeit deserted and dilapidated, still bear witness of a different, livelier past. In 1986, the year of the accident, the Ukrainian authorities created the Chernobyl exclusion zone, which is a 30 km area around the site of the nuclear disaster. About 91,000 people were evacuated from the zone. Today, some 300 people, mostly elderly Ukrainians, have returned and live in a few villages in the exclusion zone.

Radiation levels in the zone have been thoroughly researched in the past two decades, providing reliable reference points for the CTBTO exercise. The CTBTO used an area of about 100 square kilometres as the assumed inspection area for its exercise. The field area was selected for its detectable radiation anomalies. At the same time, it was important to ensure that the exposure to radioactivity would remain within acceptable limits. As the exercise took place in the Chernobyl exclusion zone, CTBTO coordinated all related matters with the Ukrainian Ministry for Emergency Situations and Affairs of Population Protection from the Consequences of the Chernobyl Catastrophe. "The Ukrainian authorities were extremely supportive during all phases of the exercise. We particularly appreciated their flexibility and resourcefulness", said Gregor Malich when speaking of CTBTO's counterparts in Chernobyl which, apart from the Ministry, also included Ukraine's National Space Agency.

Measuring radioactivity during an on-site inspection ideally starts with gamma radiation surveys. In the recent exercise, two field teams carried out these tasks. The teams conducted several surveys by helicopter and by car, refining the grids each time. As in a real on-site inspection, the findings of the gamma radiation survey teams helped the environmental sampling team to identify the areas with conspicuous radiation levels. Equipped with hand-held radiation monitors and dressed in protective overalls, the team proceeded to cut vegetation, collect objects and take soil and water samples. Everything that went for analysis was supported by information on the location where the sample was found, such as photographs and GPS readings. "There is a chain of custody like in forensics", said Malcolm Cooper who was responsible for supervising the environmental sampling and analysis during the exercise.

Cross-contamination between samples and instruments had to be precluded throughout the sampling. Everything was double-bagged and instruments were washed to prevent cross-contamination. Malcolm Cooper: "We have to make sure that the integrity of the samples is maintained." Back at the base, samples were subjected to a string of analyses to determine the level of radiation and identify the contaminant, i.e. the radioactive element that caused the radiation. All findings, including those from the surveys, the sampling and the analyses, were entered into a central data base, the Field Information Management System or FIMS. The results of the surveys and the analysis of the findings, though, were not the main focus of attention. "This field exercise is about looking at procedures", said Junichi Tanaka of the CTBTO, who oversaw the gamma radiation survey.

The testing of procedures, on the one hand, referred to actual inspection activities. On the other hand, logistics and infrastructure also needed to be tested, as every on-site inspection represents an enormous logistical challenge. When staking out the location of a suspected nuclear explosion, an on-site inspection team will most likely have to travel to very remote places with little if any infrastructure. Conditions will be entirely unknown and any eventuality will have to be dealt with on the spot. These aspects were taken into account during the exercise when, for instance, several tents were put up in the centre of town in order to create a realistic setting for the on-site inspection safe base. One of the environmental sampling teams was unlucky enough to find out just how important logistics and infrastructure indeed are. While scouring the woods for traces of radioactive contamination, their vehicle broke down, leaving the three experts stranded in the middle of nowhere. The wait for rescue was not made easier by the circumstances. It was a hot day and the experts were stuck in their protective overalls, which they had to keep on in order to reduce risks of radioactive contamination and to prevent a break in the chain of forensic evidence. In the end, the group was brought safely back to base and the unpleasantness of the incident was clearly outweighed by the experience gained towards validating OSI emergency procedures.

As an on-site inspection team would be expected to handle potentially radioactive substances, monitoring and prevention of contamination and decontamination are central features of every exercise. Utmost vigilance is required. It's not only the health of every participant at an on-site inspection that would be at stake but the overall aim of the inspection as well - collecting valid evidence of a suspected nuclear explosion. The seriousness of the matter is reflected in the diligence displayed in handling the issue of contamination during the exercise. Due to still prevailing radioactivity in the Chernobyl exclusion zone, the testing of measures to prevent contamination was not just a mock exercise. As a fundamental measure of radiation protection, each participant was equipped with dosimeters, instruments measuring a person's exposure to radioactivity. When returning to base at the end of every field day, the field teams were also subjected to elaborate contamination monitoring procedures. Everybody and everything was screened before being allowed back inside. All protective clothing was discarded in dedicated containers and all instruments were scanned before being stowed away. In addition, prior to and after the exercise, all participants underwent monitoring for possible intake of radionuclides. Post-exercise analysis confirmed that no one was subjected to dangerous levels of radiation.