Prescission and post scission neutron multiplicities in the p + ²³⁸U reaction

Nowadays, there is an increasing interest in studying nucleon-induced fission of actinides at intermediate energies, i.e., between 20 and 200 MeV due to worldwide interest in accelerator-driven systems (ADS) for nuclear applications. Such systems consist of subcritical reactors driven by neutrons produced in a spallation sub-actinide target irradiated with energetic protons. This spallation process produces also energetic secondary protons which will still significantly contribute to the overall induced reactions. Neutron-and proton-induced reactions in this energy range are among the very important ones for the ADS design. The most probable process resulting from these reactions is fission, which will be accompanied by non-negligible pre- and post-scission neutron emission which will surely affect the subcriticality aspect of the proposed ADS reactor. Therefore, it is important to study neutron multiplicities and compare them with evaluations and predictions presently used for establishing the sub-criticality concept and criteria of a reactor design. Here we report our measurements on the prompt fission neutron spectra in ²³⁸U fission induced by proton at energies 14, 18 and 23 MeV