Improvements to the macroscopic-microscopic approach of nuclear fission

M. Verriere, M. Mumpower

Submitted submitted (2020)

The well established macroscopic-microscopic (mac-mic) description of nuclear fission enables the prediction of fission fragment yields for a broad range of fissioning systems. In this work, we present several key enhancements to this approach. We improve upon the microscopic sector of nuclear potential energy surfaces by magnifying the Lipkin-Nogami equations' resolution and strengthening the Strutinsky procedure, thus reducing spurious effects from the continuum. We further present a novel deterministic method for calculating fission dynamics under the assumption of strongly damped nucleonic motion. Our technique utilizes the memoryless property of Markov Chains to produce fission yields that do not rely on the statistical accumulation of scission events. We show that our new technique is equivalent to the Metropolis random-walk pioneered over the past decade by Randrup and colleagues. It further improves upon it, as we remove the need for altering the nuclear landscape via a biased potential. With our final improvement, we calculate scission configurations using particle number projection, which affords the simultaneous calculation of both mass and charge yield distributions. Fission fragments are thus calculated from the quantum mechanical A-body states of the potential energy surface rather than the collective mass asymmetry variable (αg) of the Finite-Range Liquid-Drop Model (FRLDM) used in past work. We highlight the success of our enhancements by predicting the odd-even staggering and the charge polarization for the neutron-induced fission of $^{233}$U and $^{235}$U.

LLNL-JRNL-813628

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