In situ metrology of 85Kr plumes released by the COGEMA La Hague nuclear reprocessing plant

The IRSN (Institut de Radioprotection et de Surete Nucleaire, France) has started an in situ study of the behaviour of atmospheric releases close-by the COGEMA La Hague nuclear reprocessing plant. The study is designed to improve information on the dispersion of radioactive pollutants very close to the emission point—a 100 m height chimney. In this situation, close to the emission and height of the emission, Gaussian models generally used to predict the behaviour of atmospheric releases are not well adapted. The study is based on the characterisation of the 85 Kr emitted during normal operations of the reprocessing process. Temporal and spatial variations of the plume shape were investigated with intensive in situ measurements. Live in situ techniques to measure the electrons and the photons emitted by the 85 Kr have been implemented and will be described. Preliminary results showing the interest of the techniques were presented. Variations of the dose rates created by the photon flux of a plume were directly measured and correlated to other quantities.