The Fork Detector for Spent Fuel Measurements: Measurements and Simulations

The investigations and implementation of experimental methods for the burnup (BU) determination of spent fuel elements (SFE) is one the research areas at the Belgian Nuclear Research Centre SCK•CEN. A version of the so-called Fork Detector has been designed at SCK•CEN and is in use at the Belgian Nuclear Power Plant of Doel. The Fork Detector relies on passive neutron and gamma measurements for the assessment of the burnup of SFE and safeguards verification activities. In order to better evaluate and understand the method and in view to extend its capabilities, an effort to model both the detector and the spent fuel was made. A model of the Fork detector has been therefore developed with MCNP while the spent fuel composition and neutron intensity was obtained with the ORIGEN-ARP code. By coupling the results of these two codes one can estimate the expected detector response in a typical measurement configuration. Several fuel elements were measured in a spent fuel deactivation pool and compared with the estimated value from the simulations. The results of this comparison exercise are presented in this paper.