Evaluation of near field dispersion Lagrangien modelling with krypton 85 measurements around COGEMA La Hague nuclear reprocessing plant (France)

In order to improve the evaluation of the near field dispersion (< 4 km) for above-ground releases, the IRSN made in situ measurements of krypton 85 (85Kr) around La Hague nuclear reprocessing plant, from a release stack 100 m high (Maro et al., 2002). The continuous measurement of 85Kr activity in the air provides a useful tool for validating atmospheric dispersion models for different distances, on a large range of stability and turbulence conditions. A modelling system, PERLE, has been developed at Meteo-France, for the Crisis Meteorological Cell (CMC) of atmospheric accidental release, in case of emergency. Mesoscale meteorological fields are simulated by the non-hydrostatic MESO-NH model (8km and 2km resolution nested grids). The dispersion model used to describe the pollutant cloud in the vicinity of the release during the first critical few hours is a lagrangian particle model. Two stochastic dispersion models have been evaluated and compared: DIFPAR and SPRAY. A set of fourteen test cases has been conducted with PERLE on 85Kr measurements around La Hague. (orig.)