Comparison of GEANT4 and MCNPX-PoliMi fission models

The detection and characterization of special nuclear material (SNM) is of significant importance for nonproliferation applications. For neutron energies <;1 eV, fission is the dominating interaction process of all possible neutron-nucleus interactions, hence thermal neutron induced fission is one of the techniques that can be utilized for the characterization of the SNM. Prompt and delayed neutrons and gamma-rays are emitted per fission event. These multiplicities can be modeled using Monte Carlo techniques. However, the modeling of multiplicity distributions of prompt fission neutrons and gamma-rays is dependent not only upon statistical models but also upon tracking fission neutrons and gamma-rays on an event-by-event basis. Both Geant4 and MCNPX-PoliMi are capable of simulating particles on an event-by-event basis. In Geant4, the neutron and gamma-ray multiplicity distributions are computed using a customized fission library developed by the Lawrence Livermore National Laboratory (LLNL). The neutron and gamma-ray multiplicity distributions are also computed with MCNPX-PoliMi, which is a modified version of MCNP code. Simulations show that there is very good agreement in neutron multiplicities generated with these codes. Furthermore, various fission models can be simulated in these respective Monte Carlo codes.