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Krypton-85: a tool for investigating near field atmospheric dispersion for elevated emissions around La Hague spent fuel nuclear reprocessing plant.



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Denis Maro, Pierre Germain, Didier Hebert, Luc Solier, Marianne Rozet, Gaël Leclerc and Serge Le Cavelier actes du congrès "8th conference on harmonization within atmospheric dispersion modeling for regulatory purposes" - The national institute of meteorology and hydrology, Bulgarian academy of sciences, sofia, bulgarie 14-17 octobre 2002 Ekaterina Batchvarova and Dimiter Syrakov (Eds) - pages 138 -143.


Gaussian atmospheric dispersion models of a plume can be used to estimate the dispersion of ground-level atmospheric emissions or, in the case of high elevation emissions, distances far enough away from the source point for the plume to be close to the ground. These models have been essentially validated with ground-level or low height emission measurements campaigns (typically 10 m). The IRSN is conducting in situ near field (< 4 km) atmospheric dispersion investigations around COGEMA's La Hague spent fuel nuclear reprocessing plant (France), by using krypton-85 (85Kr), the chemically inert gas, released in the gaseous waste from release stack 100 m high as an experimental atmospheric dispersion research device. This research aims to extend the scope of application of operational models. Between 1997 and 1998, fourteen 85Kr measurements campaigns were conducted at ground level and in the center of the plume for a variety of distances from the discharge point and meteorological conditions (Maro et al., 2001). The various results confirm that 85Kr is a good tool for the proposed investigation and that at short distances there are significant deviations between the models (Doury, 1976) (Pasquill - Briggs, 1974, 1976) and the experimental results, whence the need to acquire additional data on near field plume dispersion, particularly in relation to its vertical component. In this paper, the results of more recent measurements campaigns are presented and compared with the Gaussian atmospheric dispersion model using Doury (1976) and Pasquill - Briggs (1974, 1976) standard deviations, in order to reduce the uncertainties surrounding their areas of validity.