Simulation of Prompt Neutron Spectra Following the Bremsstrahlung Interrogation of Depleted Uranium

Year
2008
Author(s)
Sara Pozzi - Oak Ridge National Laboratory
S. D. Clarke - School of Nuclear Engineering, Purdue University
S. J. Thompson - Idaho State University
Abstract
This work illustrates the capabilities of the MCNPX/MCNP-PoliMi code system for simulating the prompt neutron field generated immediately following photon interrogation of fissionable material. The simulations were compared to prompt time-of-flight data taken at the Idaho Accelerator Center immediately following the interrogation of a depleted uranium target with 7 to 18-MeV-endpoint bremsstrahlung photon beams. The MCNP-PoliMi results agree very well for the lower beam energies (less than 10 MeV). As the beam energy is increased, the MCNP-PoliMi simulations begin to overestimate the number of low-energy neutrons. These errors are similar to previous validation efforts of the MCNP photonuclear data library in other actinides. However, previous work compared only total photoneutron production; this work compares the entire energy spectrum of the produced photoneutrons. The errors in photoneutron production appear to be centered in low-energy neutrons. Further investigation is needed to completely resolve these differences.