A mixed spectral-similary method for the estimation of diffusion parameters.

O. Isnard, M. Monfort, R. Martens, H. Schnadt, Seventh International Conference on Harmonisation within Atmospheric Dispersion Models for Regulatory Purposes, 28-31/05/2001, Beligrate, Italie.

Within the framework of nuclear emergency, the early estimate of radiological consequences in the environment is a key element towards the protection of neighbouring population and the organization crisis. Thus it is necessary to have atmospheric dispersion models adapted to these early estimates, the results being used to evaluate real or potential doses. The possible risk of a nuclear accident that yield a release in the atmosphere (nuclear power plant, transport of radioactive materials) near a state border requires an harmonization of the protection measures the concern countries should take towards the public and the environment. The evalua-tion of dispersion models used in this case is necessary to settle this harmonization. The French– German Commission for Safety Problems of Nuclear Installation thus investigated on operational models (Gaussian puff dispersion in both case used in France, where the diffusion parameters are based on the transfer time, and in Germany, where the diffusion parameters are based on the distance. It was shown that there were some meteorological situations where the measures to be taken yielded significative differences. The establishment of a new common puff-dispersion model (CRABOL et al., 1999) was then decided. This work has been done with the collaboration of the Gesellschaft für Anlagen-und Reaktorsicherheit (Germany) and the Technischer Überwachungsverein Rheinland (Germany).