Design of a Prompt Gamma Activation Analysis Simulation Tool for Nuclear Forensic Characterization

A suite of simulation tools has been developed to assess potential of prompt gamma activation analysis (PGAA) for characterization of nuclear fuel cycle materials. This effort seeks to identify and utilize large neutron capture resonances in the 0.5-40 eV energy region to enhance the achievable prompt gamma response via PGAA. Several rare earth isotopes have large neutron capture cross sections in the 0.5-40 eV energy region and remain stable upon neutron capture, which makes them prime targets for analysis via PGAA. The simulation code DICEBOX calculates the production of prompt gammas from an excited nucleus. These prompt gammas are provided to a Geant4 model and used as the primary radiation source. The Geant4 model developed as part of this work is inspired by the Geant4 tools used with the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Lab, one of the world’s premier PGAA facilities. The Geant4 model simulates transport of gammas from their initial isotropic distribution within the target to a high purity germanium (HPGe) detector. Geant4 also simulates a realistic detector response as a function of gamma energy. The Geant4 model allows its simulations to realistically predict prompt gamma responses from individual isotopes of interest. By scaling these responses against expected neutron capture rates within a target, expected prompt gamma response profiles for complex, multi-elemental materials are generated. These results will provide insight into the efficacy of PGAA as a non-destructive, rapid turnaround alternative technique for forensic characterization of nuclear fuel cycle materials.