CROCUS Concrete Activation Study by γ-ray Spectrometry and TLD Neutron Flux Measurements

The semester project was under the course Physics lab IVb at EPFL. At EPFL site, the experimental fission reactor CROCUS is shielded by concrete which becomes radioactive as a result of neutron interaction. The activation is of interest to study for validation of models and cal- culations, and to quantify the amount of radioactive waste when the reactor will be recycled. In this project, measurements on concrete ac- tivation by NaI- and HPGe-detectors were performed on an in-cavity concrete block, together with TLD measurements on neutron flux in- side the core of CROCUS and in the cavity. The concrete activation and neutron flux allows for comparison and validation of models. The in-cavity concrete block had a low activation, trace elements of 60Co and 65Zn seem to be existing. The relative flux was the highest for structures close to the core and at the ceiling. In future projects, more experimental data on both concrete activation and neutron flux would be performed to acquire uncertainty estimations and correction factors.