Objectif The subsequent deposition of radioactive material released to the atmosphere during the Chernobyl accident resulted in widespread and continuing contamination of large areas of land. Many data have since been gathered on the contamination levels both in the former Soviet Union and elsewhere; these data include the concentrations and size distributions of airborne radioactive material; the properties of hot particles in the air and soil, and the time-dependent behaviour of various radionuclides in surface layers. This contamination acts as a source of continuing exposure principally from external radiation and from internal radiation due to transfer through foodchains. In addition, because of resuspension, the potential exists for a net transfer with time of material from more to less contaminated areas; such transfer processes have not been investigated in any detail and could be important in the long-term management and control of contaminated areas and, moreover, could have implications for the level to which it may be worthwhile decontaminating more heavily populated areas. This project is directed to a more detailed investigation of the potential importance of resuspension (caused by both natural and man-made phenomena) in these contexts and has the following main objectives: to predict airborne contamination levels and the levels of deposition on the rural and urban surfaces by resuspended material to assess the significance of resuspension in terms of decreasing the level of contamination of various surfaces to determine whether buffer zones are needed around contaminated areas to ensure that airborne concentrations of resuspended material are reduced to acceptable levels and, if so, to determine their magnitude in general and for specific operations, eg, ploughing, etc. The objectives will be met, firstly, by compiling and interpreting data already obtained in the former Soviet Union and elsewhere and, secondly, by performing supplementary measurement programmes within the 30 km zone around Chernobyl and elsewhere in order to gain the broadest understanding of the data. Investigations will be focused in the following areas during the second year of this project. Inhalation risks from resuspended particles in the range below 10 um The size spectrum of aerosols, in the range below 10 um, should be measured at different heights above ground in the Chernobyl area in order to assess the inhalation risks from resuspended particles. In order to relate the results to the environmental conditions, the size differential particle mass in the same range should be determined as well as the airborne radionuclide concentrations in different diameter ranges. Particular emphasis should be given to the contribution of alpha emitters and this will necessitate the development of an alpha spectrometry capability close to the measurement area. The importance of large particles in the transfer of material The following experimental studies should be performed to elucidate and quantify the contribution made by large particles to the further spreading of deposited material and to investigate the influence that various environmental and meteorological parameters have on their transfer: the measurement of the rate of spread of contamination from more to less contaminated areas the determination of the deposition of large particles as a function of height above ground level and the evaluation of the results in terms of the transport of contamination by resuspended large particles. Meteorological parameters should be measured during the experimental campaign to enable appropriate correlations to be explored and the results should be integrated with results obtained previously from experiments carried out by institutes in the former Soviet Union. In addition, an analysis should be made of the potential importance of relatively rare yet extreme meteorological phenomena or events as a means for dispersing large amounts of deposited material over considerable distances. Identification and characterisation of sources of resuspension This work should focus on the identification and characterisation of sources of resuspension with an emphasis on the potential importance of the resuspension of small and large "hot particles". The experimental programme should be directed towards the following: characterise the surface soils in the regions of Chernobyl where resuspension measurements are made evaluate the solubility of various gamma-emitting radionuclides measure suspended particulate masses in the regimes below and above 20 um diameter with a high volume sampler and collect hot particles in these two diameter ranges and characterise according to their inorganic structure. Inhalation risks from resuspended particles in the range above 10 um To complement data obtained on the height dependence of the deposition of large resuspended particles and to evaluate the potential inhalation risks from large particles, measurements should be made of the aerosol size distribution in the large diameter regime (ie, above 10 um) as a function of height above ground in the Chernobyl area. For this purpose image analysis techniques and instrumentation should be developed so that routine use can be made of rotating arm impactors with known collection efficiency and operating at three or more different heights simultaneously. In addition, new or modified dose assessment models should be developed to estimate the risk presented by the inhalation of large particles resuspended naturally or by man's activities from both urban and rural surfaces. The models should also be capable of assessing the risk from the inhalation of "hot particles". Resuspension measurement outside the former Soviet Union Significant amounts of radioactive material released during the Chernobyl reactor accident were deposited on territory outside the former Soviet Union. Measurements of resuspension in these areas can be compared with those made in the 30 km zone where the nature and radionuclide composition of the deposited material is likely to have been different. Important insights on transport and resuspension processes may be gained by such comparisons, in particular the influence of the nature of the deposited material and of the characteristics of the surface at the time the deposit occurred and subsequently. In selecting data to be analysed for this purpose, preference should be given to complete or largely complete time-series of measurements of resuspended concentrations of radioactive material in air at different heights above ground having different surface covers (eg, urban, rural, snow covered during the initial deposit, etc). Programme(s) IC-COSU C - Collaboration with the former Soviet Union in Radiation Protection, 1991- Thème(s) Data not available Appel à propositions Data not available Régime de financement CSC - Cost-sharing contracts Coordinateur GSF-RESEARCH CENTER FOR ENVIRONMENT AND HEALTH Contribution de l’UE Aucune donnée Adresse Ingolstaedter Landstrasse 1 85764 OBERSCHLEISSHEIM Allemagne Voir sur la carte Coût total Aucune donnée Participants (4) Trier par ordre alphabétique Trier par contribution de l’UE Tout développer Tout réduire CENTRO DE INVESTIGACIONES ENERGETICAS, MEDIAMBIENTALES Y TECNOLOGICAS Espagne Contribution de l’UE Aucune donnée Adresse 22,Avenida Complutense 22 28040 MADRID Voir sur la carte Coût total Aucune donnée COMMISSARIAT A L'ENERGIE ATOMIQUE France Contribution de l’UE Aucune donnée Adresse Rue de la Federation 31-33 75015 PARIS Voir sur la carte Coût total Aucune donnée FRAUNHOFER IAF Allemagne Contribution de l’UE Aucune donnée Adresse Tullastr. 72 79108 MÜNCHEN Voir sur la carte Liens Site web Opens in new window Coût total Aucune donnée UNITED KINGDOM ATOMIC ENERGY AUTHORITY Royaume-Uni Contribution de l’UE Aucune donnée Adresse Harwell 329, Marshall Building 521 OX11 0RA DIDCOT,HARWELL,CHILTON Voir sur la carte Coût total Aucune donnée
