Technical Recommendations on Measurements of External Environmental Gamma Radiation Doses (A Report of EURADOS Working Group 12 'Environmental Radiation Monitoring')

Abstract

These recommendations provide guidance and information on the measurement of dose rates in the environment arising from photon radiation both from natural sources and from man-made sources. During the past decade there has been significant interest in the levels of radiation to which the general public is exposed, both from natural causes but particularly, since the Three Mile Island and Chernobyl accidents, to that arising from man-made operations. The public concern following the Chemobyl accident prompted many countries to introduce very comprehensive monitoring systems which included national networks of dose rate monitoring systems. These systems are aimed at providing Governments with prompt warning of radioactive releases, and accurate assessment of the predicted doses to the public, following accidents at nuclear installations within their own country and from installations in neighbouring and very remote countries. The measurement of dose rates from photon radiation in the neighbourhood of a nuclear installation is an essential part of any environmental measurement programme that is necessary to demonstrate that members of the public are not exposed to unacceptable levels of radiation arising from the operation of the installation. Apart from the technical difficulties of measuring such low dose rates, there are also problems in assessing their significance in relation to the comparable, but variable, dose rates from natural sources. To help improve the quality and accuracy of environmental radiation measurements within Europe, the Commission of the European Communities (CEC) sponsored intercomparison experiments during the past ten years. The purpose of this Technical Report is to disseminate the considerable experience and expertise gained by the participants during these intercomparisons. Practical advice is given on all aspects of environmental photon dose monitoring. The report starts by describing the nature and variability of environmental gamma radiation within Europe and then discusses the quantities that should be used for measurements. The characteristics and performance of both passive and active detectors as well as of spectrometry systems are discussed. Type testing and calibration methods are recommended which will enable the response of the monitoring equipment to the different radiation components to be properly determined. Techniques for assessing the uncertainties associated with both calibration and measurements are described. Examples are given of the early warning systems installed within European countries. It is hoped that this report will assist in the harmonisation of environmental photon dose measurements within Europe and the rest of the world.