In order to perform risk assessments for severe accident and off-site emergency response (corresponding to Defence in Depth level 4 and level 5, respectively) assumed an earthquake in nuclear fuel facilities, it is necessary to consider human operations such as using portable equipment, and simultaneous occurrence of multiple accidents based on an earthquake. In order to perform such risk assessments, risk assessment methods that can consider the feedback of the effects of human operations and the behavior of equipment and the interactions between multiple accidents are necessary. However, conventional Probabilistic Risk Assessment (PRA) techniques are insufficient to analyze such accidents because these techniques are static analysis methods assuming that accidents occur due to component failures or operation errors. In this study, in order to enable such analysis, the authors introduced STAMP/STPA (Systems Theoretic Accident Model and Process/System Theoretic Process Analysis) method (Leveson, 2012) which is a dynamic accident model based on system theory and constructed an interaction multi-layer model in order to link it with the static analysis model such as the conventional PRA method (Mori, 2019). As one of the remaining problems of this model, the STAMP/STPA method that constitutes this model is a qualitative evaluation method, so it is necessary to study a method for quantitative evaluation