A study of the near field atmospheric dispersion of emissions at height: Comparison of Gaussian plume models (Doury, Pasquill-Briggs, Caire) with krypton 85 measurements taken around La Hague nuclear reprocessing plant

¹ Institut de Protection et de Sûreté Nucléaire, Département de PRotection de l'Environnement, Service d'Études et Recherches Radioécologiques dans les Milieux NATurels, LERFA, 50130 Cherbourg-Octeville, France
² Institut de Protection et de Sûreté Nucléaire, Département de Protection de l'Environnement, CE-Saclay, bâtiment 130, 91191 Gif-sur-Yvette, France
³ Marine Nationale, Groupe d'Études Atomiques (GEA), BP. 34, 50115 Cherbourg Naval, France
⁴ Institut de Protection et de Sûreté Nucléaire, Département de Protection de l'Environnement, LMRE, Bois des Rames, bâtiment 501, 91400 Orsay, France

Abstract

Gaussian atmospheric dispersion models are principally validated for release at ground level, or, if the release is very high up, at distances sufficiently removed from the source for the plume to have reached the ground. In order to improve the evaluation of the near field dispersion (< 4 km) for above-ground releases, the Institute for Protection and Nuclear Safety (IPSN) began an in situ study in June 1997 around the La Hague nuclear reprocessing plant using krypton 85 (⁸⁵Kr, released in the gaseous effluent by a stack of 100 m high) as a plume tracer. The aim of this study is to compare the results for the atmospheric transfer coefficients (ATC) obtained in ⁸⁵Kr measurement surveys with the results of three Gaussian atmospheric dispersion models (Doury, Pasquill-Briggs and CAIRE) in order to define the distances at which corrections need to be made to the models and thus improve determination of the ATCs. For all the results, it is observed as expected that the models are not applicable for the source near field; however, the study clearly shows that the CAIRE model gives the best results at all distances.