Conference Papers Year : 2024

Towards a highly efficient and unbiased population-control algorithm for kinetic Monte Carlo simulations

Abstract

Population-control methods are key to non-stationary Monte Carlo simulations of multiplying systems: they prevent either the unbounded growth or the disappearance of neutrons, occurring respectively in supercritical and subcritical conditions; furthermore, they contribute to an efficient allocation of computational resources by addressing the unbalance between the neutron and the precursor populations. In this paper, we present two alternative populationcontrol algorithms: the legacy implementation in TRIPOLI-4®, the Monte Carlo code developed at CEA, and an improved version that is currently under investigation, based on the use of a simplified point-kinetics solver. We assess the performance of these methods through the simulation of a $2.2 step reactivity insertion in a fast system (Flattop-Pu), leading to an increase of the neutron population by a factor 200, which is benchmarked against point kinetics. We show that the new implementation not only suppresses the slight bias that was present in the legacy method due to a stochastic normalization factor, but also outperforms the previous algorithm in terms of variance reduction and improvement of the figure of merit.

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hal-04889126 , version 1 (15-01-2025)

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Cecilia Montecchio, Vincent Lamirand, Davide Mancusi, Wilfried Monange, Andrea Zoia. Towards a highly efficient and unbiased population-control algorithm for kinetic Monte Carlo simulations. International Conference on Supercomputing in Nuclear Applications + Monte Carlo, SNA + MC 2024, Oct 2024, Paris ( France), France. pp.09006, ⟨10.1051/epjconf/202430209006⟩. ⟨hal-04889126⟩
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