Cross Section Calculations for Fission Reactions Induced by Intermediate Energy (100 MeV – 1 GeV) Nucleons and Monte Carlo Simulation of Neutron Flux at n_TOF Facility (CERN)

Fission induced by nucleons at intermediate energies is important in both fundamental and applied nuclear physics. From a fundamental viewpoint a theory able to describe nucleon induced fission over a broad range of target nuclei and a wide interval of projectile energies is still lacking; therefore, Monte Carlo simulations able to reproduce the sparse data on (p, f) and (n, f) reactions at intermediate energies constitute a valuable integration. From an applied viewpoint, the above mentioned data are very important for energy production, radioactive waste transmutation and radiation shield design for accelerators. In particular, high-accuracy data of neutron-induced fission cross sections are essential to the design of Generation IV reactors and, as far as neutron intermediate energies are concerned, of accelerator-driven subcritical systems (ADS). Monte Carlo calculations of fission of actinides and pre-actinides induced by protons and neutrons in the energy range from 100 MeV to 1 GeV are carried out by means of a recent version of the Liège. Intranuclear Cascade Model, INCL++, coupled with two different evaporation-fission codes, GEMINI++ and ABLA07. In order to reproduce experimental fission cross sections, model parameters are usually adjusted on available (p, f) cross sections and used to predict (n, f) cross sections for the same isotopes. The model INCL++, coupled with ABLA07, has also been used within Monte Carlo simulations based on the code GEANT4. The spallation target of the experiment n_TOF (CERN) has been simulated in order to make a detailed study of the neutron flux generated by the proton beam (20 GeV) that interacts inside it. Preliminary results have been compared with experimental data and simulation data obtained by the FLUKA code.