Transient fission matrix approach for assessing complex kinetics behavior in the ZEPHYR ZPR coupled core configurations

•Transient Fission Matrix is tested on the fast/thermal coupled lattice of the future ZEPHYR critical facility.•Coupling phenomena between heterogeneous zones are explained, through transmission probabilities of prompt and delayed neutrons.•TFM as a correlated sampling method is tested for perturbation analysis.•The TFM can be used as a powerful tool to develop innovative design approaches in core physics.•The TFM, coupled to multipoint approaches, can help the physicist to design high dominant ratio lattices, and challenge future experiments in ZEPHYR.