As part of the circular economy, a major objective is to facilitate the recycling of strategic materials needed by industry. This requires, first of all, the ability to accurately locate them in industrial components that are no longer in use. Non-destructive nuclear measurement meets this objective, based on prompt gamma neutron activation analysis (PGNAA). This approach involves interrogating the samples to be analyzed with an electrical generator emitting pulses of fast neutrons that thermalize in a polyethylene and graphite cell: between the pulses, radiative capture gamma rays are measured. The advantage of such an approach lies in the fact that high-value elements such as dysprosium or neodymium have a high radiative capture cross-section by thermal neutrons, and that the latter can probe deep into large volumes of matter (several liters).
A previous thesis demonstrated the feasibility of this technique and opened up promising avenues of research, with two complementary strands to make concrete progress towards practical recycling objectives. The first involves experimental and simulation studies of the performance of gamma cascade measurement on cases representative of industrial needs (size and composition of objects, measurement speed). The second will enrich and improve the exploitation of the vast amount of information available from gamma-ray cascade measurements.
In practice, the work will be carried out as part of a collaboration between CEA and the FZJ (ForschungsZentrum Jülich) institute in Germany. The first half of the thesis will be carried out at CEA IRESNE Nuclear Measurement Laboratory. The second half of the thesis will be carried out at the FZJ (Jülich Centre for Neutron Science, JCNS). The German part of the thesis will involve experiments with the FaNGaS device at the Heinz-Maier-Leibnitz Zentrum (MLZ) in Garching.