Decommissioning of CESNEF l-54m research reactor: Radiological pre-characterization of graphite and biological shield

The L-54M thermal research reactor was commissioned by Politecnico di Milano to Atomic International in 1958. It was shut down in 1979 after around 20 years of operations for research purposes. Subsequently it was put under Safe Storage. Several operations have to be managed in order to restore the reactor site to the status of "unrestricted re-use", the socalled "greenfield" status. This work concerns the preliminary radiological characterization of graphite and concrete, which are the main constituents of the moderator/reflector and the biological shield respectively. The main purpose of this work is the assessment of conventional and radioactive wastes volumes in view of the final decommissioning. In this context, the key radionuclides deriving from neutron activation are: ³H, ¹⁴C, ⁶⁰Co, ¹⁵²Eu. The first part of the research was based on neutron diffusion theory for the computational evaluation of the activity of these activation products. The second part of the work was focused on Non-Destructive Analyses (NDA) and DA of few graphite and concrete representative samples