Radiological Characterization Studies for the CNGS Dismantling

Abstract

A comprehensive study of the radiological CNGS (CERN Neutrinos to Gran Sasso Experiment) environment characterization is presented. It comprises the evaluation of the residual dose rates of the most relevant standalone beam line equipment, such as the target and horn, as well as overall dose levels in the cavern before and after dismantling. Furthermore, the radionuclide inventories of the main objects to be dismantled were calculated by the Monte Carlo FLUKA code and ActiWiz. The latter is particularly important for transport and waste management. Moreover, we present benchmarking measurements of residual dose rates in the experimental cavern, staying in good agreement with simulation predictions. Additional measurements, as well as FLUKA and ActiWiz studies, allowed for assessing the concrete composition of the cavern’s walls and floor and the shielding blocks. The resulting refined composition allowed for evaluating more precisely the radionuclide inventories and residual dose rates expected before and after the dismantling in the CNGS target area. This was particularly important for the evaluation of the dismantling cost and the substantial savings due to the reusage of the majority of the concrete blocks. Finally, contamination measurements in the accessible parts of the area also are included. All the results discussed are crucial for determining the requirements, planning, and costs of the CNGS dismantling.