Physics-based fission event generators model the complex dynamics of the nuclear fission process and produce correlated neutrons and gamma-rays for Monte Carlo simulations. These correlated sources of simulated particles are important in nonproliferation and safeguards application; the accurate characterization of a fissionable sample depends on the properties of the neutrons and gamma rays accompanying fission. Multiplicity counting techniques rely on the correlation between detected multiplicities to estimate the activity of a fissionable sample. However, these techniques assume multiplicity-independent fission spectra, since no dependence has ever been experimentally reported. Fission event generator, using statistical model of fission fragment de-excitation predict complicated, non-linear correlations in the energies and multiplicities of neutrons emitted following fission. We distinguish between two types of correlations: variations in the average spectra of neutrons with multiplicity, and correlations in the energies of neutrons emitted within the same fission reaction. Using simulations and model-based calculations, we estimate how each of these correlations can bias the results of multiplicity counting with organic scintillators.
Year
2020
Abstract