ASTRAL est acronyme d'u assistance technique en radioprotection postaccidentelle ». Si un rejet important de radionucléides dans l'environnement se produisait, il faudrait rapidement évaluer la concentration des radionucléides dans les milieux et les produits alimentaires, en déduire l'exposition potentielle aux rayonnements des populations concernées, prévoir l'évolution de la situation et proposer différents scénarios de gestion des zones contaminées. A ces fins, il a été décidé il y trois ans environ de créer un logiciel utilisable par un ensemble relativement large d'agents gréant les centres de crise, réalisant des études prévisionnelles, ou s'occupant habituellement du contrôle de l'impact des rejets de routine. Le point de départ des estimations est le dépôt sur le sol des radionucléides. La phase de dispersion atmosphérique et les conséquences de l'exposition au nuage et aux radionucléides à vie courte ne sont pas traitées ici. Les calculs effectués concernent à la fois l'évolution dans le temps des concentrations des radionucléides dans les sols et les éléments de la chaîne alimentaire, ainsi que l'évaluation des doses efficaces dues à l'exposition externe et interne. Ces grandeurs sont comparées aux limites et niveaux d'intervention en vigueur. Différentes simulations de la gestion des zones contaminées peuvent être conduites par application de contre-mesures. Ainsi, le logiciel ASTRAL peut être utilisé comme un élément d'aide à la décision.ASTRAL : a Fofhvare for the estimation of accidental release of radionuclides in the environment. ASTRAL is an acronym for "radioprotection in post accidental situation". Should an important release of radionuclides in the environment occur, it would be necessary to rapidly assess the concentration of radionuclides in the environment and in the element? of the food Chain, derive from that the potential exposure of concerned populations to the radiations, forecast the evolution in t h e of this exposure and propose different scenarios of remediation actions in the contaminated zones. For this purpose it was decided three years ago to create a software fit for a relatively large group of personnel involved in the management of radioactive releases, or staffing crisis centres. The starting point of the evaluations is the ground deposition of radionuclides. The atmospheric dispersion phase, the exposure to the plume and to short-lived radionuclides is not treated here. The calculations performed concern the evolution in time of concentrations in the soi1 and the elements of the food-Chain, and the evaluation of the doses due to externat and interna1 exposure. The results are compared to the admissible limits and intervention levels. Different simulations of management of contaminated zones, hy implementation of countermeasures may he conducted. So, the ASTRAL software may he used as an element for decision making.
The French radioecological assessment model ASTRAL and the German model PARK have been developed to evaluate the radiological situation in the case of an accidental release of radionuclides and a widespread contamination of the environment. For decision makers it is of importance that the results on foodstuff contamination and on dose to humans are in fairly good agreement, when areas of the common border are affected. Therefore a comparative study has been done for two scenarios, assuming accidental releases on 1 June and 1 October. The study indicates that the models' structures and the transfer parameters are in good agreement. Only model principles for root vegetables are different in both models. Significant differences in results on the contamination of foodstuff and on dose to humans by ingestion are caused by different assumptions on dates of harvest and feeding methods of animals. A corresponding harmonization is essential with respect to decision making.
From 1988 to 1993, the Nuclear Safety and Protection Institute (Institut de Protection et de Sûreté Nucléaire--IPSN) conducted experimental programs focused on transfers to vegetation following accidental localized deposits of radioactive aerosols. In relation to vegetable crops (fruit, leaves, and root vegetables) and meadow grass these experiments have enabled a determination of the factors involved in the transfer of cesium, strontium, and ruthenium at successive harvests, or cuttings, in respect of various time lags after contamination. The dynamic modeling given by these results allows an evaluation of changes in the mass activity of vegetables and grass during the months following deposit. It constitutes part of the ASTRAL post-accident radioecology model.
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