Three-dimensional simulation framework of personnel evacuation integrating social force and radiation fields during LBLOCA in Floating Nuclear Power Plants

This study presents a three-dimensional simulation framework integrating crowd dynamics, human behavioral factors, and time-dependent radiation fields to quantitatively assess evacuation efficiency and individual radiation exposure during large-break loss-of-coolant accidents (LBLOCA) on floating nuclear power plants (FNPPs). The evacuation module extends the social force model into three-dimensional space, employing the Verlet integration scheme with viscous damping to resolve pedestrian kinematics. A herding effect is incorporated to capture collective responses induced by panic during FNPP emergencies. Concurrently, a radionuclide dispersion model is formulated to represent the combined effects of bulkhead gap leakage, natural aerosol deposition, and the external re-entry of radioactive plumes from engineered safety features during LBLOCA. To validate the framework and evaluate the impact of spatial bottlenecks, numerical evacuation experiments are conducted on a simplified FNPP layout with systematically varied exit and stair widths. Results indicate that in single-compartment layouts with a single exit, evacuation time increases marginally beyond 7 occupants, and exit width exerts negligible influence on the duration. In configurations with a single staircase, stair width becomes a dominant factor, and the disparity in evacuation time increases once the occupant count exceeds 12. In inter-deck, multi-compartment FNPP layouts, stair capacity emerges as the dominant bottleneck over exit capacity. The coupled model elucidates the relationship between prolonged evacuation times and elevated individual radiation doses, indicating that the evolving radionuclide dispersion patterns during an LBLOCA play a determinative role in exposure risk. This framework offers a quantitative basis for optimizing emergency egress design and radiological protection strategies in FNPPs.