Calculating the effective delayed neutron fraction in the Molten Salt Fast Reactor: Analytical, deterministic and Monte Carlo approaches

• DOI: 10.1016/j.anucene.2013.10.015
• Publication Date: 2013-11-21T22:02:23Z
• Authors: Manuele Aufiero; Mariya Brovchenko; Antonio Cammi; Ivor Clifford; Olivier Geoffroy; Daniel Heuer; Axel Laureau; Mario Losa; Lelio Luzzi; Elsa Merle-Lucotte; Marco E. Ricotti; Hervé Rouch
• Keywords: Circulating-fuel; Molten Salt Reactor; Molten Salt Fast Reactor; Effective delayed neutron fraction; Monte Carlo; OpenFOAM; 0202 electrical engineering, electronic engineering, information engineering; 02 engineering and technology; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]; 530; 7. Clean energy

This paper deals with the calculation of the effective delayed neutron fraction (βeff) in circulating-fuel nuclear reactors. The Molten Salt Fast Reactor is adopted as test case for the comparison of the analytical, deterministic and Monte Carlo methods presented. The Monte Carlo code SERPENT-2 has been extended to allow for delayed neutron precursors drift, according to the fuel velocity field. The forward and adjoint eigenvalue multi-group diffusion problems are implemented and solved adopting the multi-physics tool-kit OpenFOAM, by taking into account the convective and turbulent diffusive terms in the precursors balance. These two approaches show good agreement in the whole range of the MSFR operating conditions. An analytical formula for the circulating-to-static conditions βeff correction factor is also derived under simple hypotheses, which explicitly takes into account the spatial dependence of the neutron importance. Its accuracy is assessed against Monte Carlo and deterministic results. The effects of in-core recirculation vortex and turbulent diffusion are finally analysed and discussed.