Initial characterisation of radioactive effluents in tanks before dismantling - 000208

This paper describes the data collection process to obtain authorisation to dismantle the former effluent treatment facility at the CEA Cadarache centre. The characterisation concerns the 127 tanks in the facility. Both intrusive (tank opening and residue sampling) and non-intrusive (gamma spectrometry measurements outside the tanks) investigations were performed on seven tanks considered to be representative of the facility's processes, i.e. effluent decontamination by filtration or evaporation. The radiochemical analysis (currently underway) of the residue samples collected aims at providing us with the input data required to define the cleaning and dismantling operations for the facility equipment. The preliminary results so far highlight a benchmark radiological spectrum of the filtration process that covers the residues in the tanks associated with this process. An apparently constant Pu isotopic composition is also observed. The different results, gathered with different methods on a first tank, show good consistency. The samples of this first tank are globally homogeneous in terms of spectrum. Analyses performed on samples from six other tanks are under study in order to confirm if it is feasible to consider using ¹³⁷Cs as a tracer for characterisation of residues, even with a strong alpha component. (authors)