Validation of a free release measurement facility on a decommissioning site

The paper summarizes measurements and the Monte Carlo simulations performed to adapt the high purity germanium (HPGe) detectors of the system to the particular tasks of the decommissioning site. The work carried out for the installation and adaptation in CIEMAT of the prototype 'SuperMum', developed in the framework of the European MetroDecom II project for segregation and declassification of materials is described. The activities related to the validation of the prototype for the specific needs of a real Waste Management Unit are presented. Monte Carlo models of the SuperMum have been developed at CIEMAT and CMI using different codes and adapted to the geometries used (big-bag containers with the material volume of up to 0.5 m³). Uncertainty budget reporting tailored for the possible deviations between Monte Carlo assumptions and real waste have been analyzed. Data for several filling levels and activity distributions have been measured with reference sources and a good agreement has been obtained with calculated values.