In the general framework of transient coupled calculations, new developments of an accurate neutron kinetics model able to characterize spatial decoupling are described, together with an application to sodium fast reactors.
The first paper presents the adaptation of the spatial kinetic Transient Fission Matrix (TFM) approach to fast neutron spectrum heterogeneous cores. This TFM approach is based on a neutronic Monte Carlo pre-calculation, condensing the time dependent response of the system in Green functions. The new developments presented here concern the addition of a correlated sampling technique that takes into account the impact of local perturbations (coolant density, Doppler effect) on the neutron transport.
The second paper is dedicated to a validation of this kinetic approach on sodium fast reactors. An application case representative of an assembly of the low void effect sodium fast reactor ASTRID is used to study the physics of this kind of system, illustrating the interesting capabilities provided by this approach and highlighting new possible calculation schemes. Different comparisons have been performed with direct Monte Carlo and ERANOS deterministic SN calculations on flux redistribution and reactivity estimation, together with calculations of local point kinetics feedback distributions.