The main objective of the TRACES 2015 cruise is to help assess the proportion of the known quantities of radionuclides released that will be fixed onto sediments, as well as the kinetics and extent to which these radionuclides can become bioavailable to living organisms (AREVA-INDIGO programme). The studied area covers the Normano-Breton Gulf. The strategy for sampling bottom sediments was based on collection of the surface layer using a Shipeck grab on sites distributed across the entire Normano-Breton Gulf. The seawater was automatically sampled at regular intervals to check the representativity of the MARS hydrodynamic model. The tritium released from the AREVA-NC, which is associated with HTO molecules and thus strictly soluble, was used as a tracer of water masses. Algae and limpets were collected at three offshore sites to supplement the regular coastal sampling. The TRACES 2015 cruise was also used to test new measuring instruments for collecting physical data. These instruments appear promising for improving our knowledge of hydro-sedimentary processes which need to be better integrated into models (AMORAD/MARIN/SEDI programme).
Philippe Laguionie (Cherbourg-Octeville Radioecology Laboratory)