Objetivo AFTER A NUCLEAR INSTALLATION HAS BEEN DECOMMISSIONED, THE LAND ON WHICH THE REACTOR BUILDING AND OTHER STRUCTURES WERE SITED WILL BE AVAILABLE FOR INDUSTRIAL, RESIDENTIAL OR AGRICULTURAL USE. BEFORE SUCH A CHANGE IN USE CAN BE ACCEPTED, IT IS ESSENTIAL THAT THE SITE IS MONITORED TO DETERMINE WHETHER ANY RESIDUAL ACTIVITY IS PRESENT IN THE SITE MATERIAL. STANDARD SAMPLING TECHNIQUES THAT MAKE USE OF CORE SAMPLES OF SITE MATERIAL ARE PROHIBITIVELY EXPENSIVE WHEN IT COMES TO DETECTING LOCALIZED SOURCES OF ACTIVITY. HOWEVER, SURVEY TECHNIQUES, USING PORTABLE EQUIPMENT LOCATED ON THE SITE, CAN BE USED TO DETECT LOCALIZED SOURCES (THOUGH ONLY INDIRECTLY IN THE CASE OF ALPHA AND BETA EMITTERS). THIS RESEARCH PROGRAMME IS CONCERNED WITH A SURVEY TECHNIQUE THAT IS USED TO DETECT LOCALIZED SOURCES OF GAMMA EMITTERS. THIS TECHNIQUE MAKES USE OF AN ADAPTIVE MOVING ARRAY DETECTOR SYSTEM, CONSISTING OF AN ARRAY OF DETECTORS, DRAWN ALONG THE SURFACE OF THE SITE. SPECTRA, ACQUIRED AT PERIODIC INTERVALS, ARE ANALYSED IN REAL-TIME TO DETERMINE THE LIKELIHOOD THAT A GAMMA SOURCE IS PRESENT IN THE REGION SCANNED. SCANNING IS DATA ADAPTIVE - THE TIME SPENT SCANNING A REGION OF THE SITE IS RELATED TO THE LIKELIHOOD THAT THE REGION CONTAINS A GAMMA SOURCE. THE OBJECTIVE OF THIS WORK PROGRAMME IS TO DETERMINE THE SCANNING TIME PER UNIT AREA FOR THIS TECHNIQUE IN TERMS OF THE INTENSITY OF THE LOCALIZED GAMMA-SOURCE, THE ENERGY OF THE EMITTED GAMMA-RAY, THE DEPTH OF THE SOURCE BELOW THE SITE SURFACE, AND THE COMPOSITION OF THE SITE MATERIAL. The principal objective of this research has been to provide information on cost effective techniques to detect localised areas of gamma emitting radionuclides. This objective has been achieved by determining the time required to scan unit area as a function of depth of the gamma source below the site surface, the activity of the gamma source, the energy of the emitted gamma ray, and the gamma transport properties of the site material. A comparison between survey and sampling techniques has been made, and the advantages of using survey techniques to detect localised gamma ray sources discussed. A survey technique based on an adaptive moving array detector system has been described. A field experiment has been carried out to verify the results of calculations of the sensitivity of the techniques described.B.1. DETERMINATION OF THE RADIATION DETECTOR SYSTEM RESPONSE FUNCTION IN TERMS OF THE DETECTOR-SOURCE GEOMETRY, THE LINEAR ATTENUATION COEFFICIENT OF THE SITE MATERIAL AND THE DISTRIBUTION OF RADIONUCLIDE ACTIVITY. B.2. CONSTRUCTION OF STOCHASTIC MODEL OF THE DETECTOR SYSTEM RESPONSE IN TERMS OF THE LINEAR ATTENUATION COEFFICIENT OF THE SITE MATERIAL, THE DISTRIBUTION OF RADIONUCLIDE ACTIVITY AND THE STOCHASTIC PROCESS GOVERNING RADIOACTIVE DECAY. B.3. DETERMINATION OF THE LINEAR ATTENUATION COEFFICIENT OF COMMON SITE MATERIALS AS A FUNCTION OF MOISTURE CONTENT AND GAMMA-RAY ENERGY. B.4. DEVELOPMENT OF A COMPUTER PROGRAM TO ESTIMATE RADIONUCLIDE ACTIVITY, WITH PARTICULAR ATTENTION TO THE DEPTH OF A POINT SOURCE BELOW THE SITE SURFACE. B.5. DEVELOPMENT OF A STOCHASTIC PROCESS FOR THE COUNT RATE OF A MOVING DETECTOR SYSTEM, AND THE CONSTRUCTION OF A STATISTIC TO TEST THE HYPOTHESIS THAT NO LOCALIZED ACTIVITY SOURCE IS PRESENT IN THE SITE. Ámbito científico natural sciencesphysical sciencesnuclear physicsnuclear decaynatural sciencesmathematicspure mathematicsgeometrynatural scienceschemical sciencesnuclear chemistryradiation chemistry Programa(s) FP1-DECOM 2C - Research programme (Euratom) concerning the decommissioning of nuclear installations, 1984-1988 Tema(s) Data not available Convocatoria de propuestas Data not available Régimen de financiación CSC - Cost-sharing contracts Coordinador IMPERIAL COLLEGE OF SCIENCE, TECHNOLOGY AND MEDICINE Aportación de la UE Sin datos Dirección South Kensington Campus LONDON Reino Unido Ver en el mapa Coste total Sin datos
