Radiation monitoring strategy in nuclear or radiological emergencies

Full text: Radiation measurements provide indispensable data needed for the management of a nuclear or radiological emergency. There must exist pre-prepared emergency monitoring strategies, with accompanying procedures and methods, that help the authorities to perform measurements efficiently and, consequently, to evaluate the radiological situation correctly and to carry out proper countermeasures on time. However, defining a realistic yet comprehensive radiation monitoring strategy for emergencies is far from being an easy task. The very concept of 'emergency monitoring strategy' should be understood in a broad sense. In an ideal case, a strategy has interfaces with all related emergency and information exchange arrangements and agreements both at the national and international level. It covers all activities from the recognition of a potential hazard situation to environmental sampling performed during the late phases of an accident. It integrates routine-monitoring practices with the special requirements set by emergency monitoring and the use of fixed monitoring stations with that of mobile measurement teams. It includes elements for gathering, analyzing, transmitting and presenting data, as well as for combining them with different kinds of forecasts. It also takes into account the various intrinsic characteristics of possible threat scenarios and contains options for adapting measuring activities according to prevailing environmental conditions. Furthermore, a strategy must have relevant links to the social and economical realities and to the primary interests of different stakeholders. In order to assist individual countries in establishing national strategies, international organisations (IAEA, OECD/NEA, EU) have published basic guidelines for emergency response and radiation measurements. Nuclear accidents, especially the Chernobyl case with its large-scale environmental consequences, and other kinds of shocking events (like the one on September 11, 2001) have enhanced harmonization and international co-operation in the field. There are, however, remarkable variations in the practical l approaches chosen by different countries in relation to emergency monitoring. This is due to the fact that the conditions, attitudes and emphases concerning the various factors affecting the contents of monitoring strategies and performing of measurements are not similar in every country. The factors needed to be considered in a strategy can be roughly categorized as belonging to one of two groups: 'Static' factors whose status or related contents are known or available before any nuclear or radiological emergency arises. Examples include population distribution, geography and topography, land use, legislation and official agreements, fixed potential sources (nuclear facilities etc.), routine monitoring arrangements and resources allocated to emergency monitoring (measuring equipment, capacity of laboratory measurements, extra manpower, decision-aiding systems with auxiliary support material). These factors cannot normally be changed quickly, at least not during the early or intermediate phases of an accident. 'Dynamic' factors whose contents will become clear only at the beginning (or during the course) of an accident or a specific event. The scenario (source term, location) and prevailing environmental conditions (e.g. weather) are the most evident items in this group. In addition, the amount and nature of resources actually available at the time may be quite different compared to those listed up in the connection with the static group: there may be a holiday season and some of the key personnel are absent, some of the equipment may be broken or there may emerge serious hardware or software problems with computers and data communication systems. Source term characteristics, event location and environmental conditions determine the nature and timing of measurements, as well as the proper measurement places. Therefore, an important connection between the two categories is the advance identification of likely scenarios and their possible consequences in different weather situations. All information of this kind also helps to link the root-level measuring activities with the other elements of an emergency monitoring strategy. An emergency monitoring strategy includes various items and interfaces ranging from international agreements to such practical details as the optimum speed of a car when searching for orphan radiation sources. Integrating all these into a well-organised and versatile unity calls for a systematic procedure. One possibility of tackling the problem as a whole is to first try to find all factors involved, then to draw up a list of questions like Which are the likely scenarios', 'What is the purpose of different types of measurements' and 'How are we able to arrange monitoring in all kinds of scenarios', and then to try to answer them. The above type of approach, though being rather simple, combined with common sense can constitute a useful tool in the strategy planning. It has to some extent been applied in a few international guides and recommendations, too. Regardless of the procedure used when planning it, a monitoring strategy must be tested in routine conditions: first in table-top exercises and drills and then in large-scale emergency exercises including field measurements. When appropriate, a strategy should be modified and updated to take better into account, for example, the challenges posed by new threats, the technical development and the changes in national and international arrangements. (author)