There is currently no operational technique capable of continuously measuring the reactivity of nuclear systems—that is, their distance from criticality—during low-power operation. This issue is of major importance, for example, for power reactors during the fuel loading phase. In these subcritical systems driven by weak sources, the average detector signal provides little information; by contrast, the temporal fluctuations in the neutron signal — stochastic neutron noise, arising from the fundamental randomness in the number of neutrons emitted by fission — provide direct and quantitative information on the multiplication process. This work, carried out as part of the SENTINELLE project proposed by the CEA, aims to develop a deterministic GPU-based solver for the moment equations (mean and correlations) of the neutron population, enabling the rapid calculation of noise observables (Feynman-a, Rossi-a, local multiplicities). The solver will then be validated using experimental data from the SENTINELLE project.