Two Approaches for Dose Assessment: Modelling and Monitoring. A. Despres, M. Chartier, H. Mansoux, C. Rommens, and P. Hubert, Institut de Protection et de Sûreté Nucléaire, Département de Protection de la santé de 1+Homme et de Dosimérie, Service d+Evaluation et de Gestion des Risques, IPSN, BP 6, F-92265 FONTENAY-AUX-ROSES Cedex, France
Assessments of population doses due to the radioactive effluents of nuclear installations in normal conditions is an important issue, especially when epidemiological controversies are at stake. Such assessments are generally based on models, assumptions and scenarios that figure dispersion and transfers of the nuclides in the various compartments of the environment. However, another approach of dose assessment can rely on field measurement of radioactive contamination measured in the environment and in foodstuff. Although differences are not dramatic, results may be conflicting. Such monitoring-based dose assessments are often viewed by the authorities or the population as more credible because they are free from the potential flaws of the modelling approach. A methodological synthesis based on two case studies on actual installations, namely the French Marcoule and Malvesi nuclear installations, shows that in fact both approaches do not yield the same impact and that each one has pros and cons. Results from both case studies show that they are dependant on the local situation. Nevertheless general conclusions can be derived. Monitoring do not capture those radionuclides whose concentration is below detection levels. Conversely, observations point out distortions in modelling. At present, theoretical and empirical approaches are handled separately.
But both modelling and monitoring methods should not be opposed but combined. The credibility of such a combined modelling-monitoring dose assessment would be greatly enhanced and should be performed systematically for the major nuclear installations. This would moreover improve the models though the feedback from field experience and would improve the monitoring, because models are useful to validate sampling strategies. A working group set up by the French authorities has agreed on the need to develop such approaches.
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