Correlated Prompt Neutron and Gamma Ray Signatures from Fission

Nuclear fission is a complex process whereby a heavy nucleus splits into two, or more, smaller fragments, releasing radiation in the form of neutrons and gamma rays. Current models and data libraries for these correlated prompt emissions are often limited, poor, or/and incorrect, even for important isotopes of uranium and plutonium. Improving our ability to accurately predict the fission emissions of these key isotopes is paramount when designing the next generation of safeguards and nonproliferation systems. To this end, we have measured the prompt neutrons and gamma rays from spontaneous (252Cf, 240Pu) and neutron-induced (235U) fission at the University of Michigan, the Joint Research Centre in Ispra, Italy, and at the Los Alamos National Laboratory LANSCE facility. In addition, we have explored fission theoretical models of the FREYA and CGMF codes and compared them to the data-driven approaches in the MCNPX-PoliMi code. In the full paper, we will present a comparison of experimental data and the output of the various theoretical and data-driven simulations; particular interest will be given to correlated particle events.