In situ metrology of 85Kr plumes released by the COGEMA la Hague reprocessing plant.
R. Gurriaran, D. Maro, P. Bouisset, D. Mekhlouche, L. Solier
In situ nuclear metrology as a tool for radioecology, Fleurus Belgium I.R.E. 10-12 June 2002
Journal of Environmental Radioactivity, 72, 137-144 (2004)
The IRSN has started an in situ study of the behaviour of atmospheric releases close-by the COGEMA la Hague reprocessing plant. The study is designed to collect 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, the gaussian models generally used to predict the behaviour of atmospheric releases are not well adapted.
The IRSN study is based on the characterization of the 85Kr emitted during normal operations of the reprocessing process. This radionucleide is hence used as a tracer of the shape of the plumes emitted by the chimney.
The study requires intensive in situ measurements in order to characterize different parameters of the plume such as the temporal and spatial variations. The peculiarities of the 85Kr decay were successfully used to this effect:
- the electrons emitted by this beta decay giving short-range information,
- the low probability (0.4 %) 514 keV photon giving access to a more global information
Live in situ techniques to measure the electrons and the photons have been implemented and will be described in this paper. Also, the variations of the external ambient dose rate were directly measured and correlated to other quantities.