The research work presented in this paper shows the feasibility of the modeling of the feared event consequences by means of Stochastic Hybrid Automata, implemented in the PyCATSHOO software. The purpose of this work is multiple since it is to show firstly the ability of PyCATSHOO to simulate the recovery of a feared event into a complex system, secondly its ability to model and simulate the physical phenomenon by an external software in 3D (Code_Saturne opensource software) and finally to optimize the path of the human operators during the repair process. The coupling approach was established and the models tested separately: calculation of convection/diffusion (by Code_Saturne) and calculation of safety measures and repairmen paths optimization during their interventions (by PyCATSHOO) based on a pollutant concentration obtained previously. This approach and its software implementation are innovative because allow to integrate a complex 3D physics in a safety assessment approach dedicated to simulation of the consequences of a feared event in addition to risk prevention. The obtained results prove the ability of PyCATSHOO to model, simulate and assess this kind of real systems and to use a solver to describe complex physics of convection/diffusion of pollutants. Theoretical methodologies to optimize the coupling approach were explored and solutions will be implemented.