Abstract: In order to quantitatively evaluate the thermal radiation hazard caused by a fireball in a chemical plant, FDS software was used to simulate the evolution of the fireball, and Pathfinder software was used to simulate the occupant evacuation. On the basis of data output by FDS and Pathfinder, the data query algorithm was written to acquire the thermal radiation dose of each evacuee, so as to calculate the casualty probability according to the dose-response model, and to determine the number of casualties. The results showed that as the fuel mass of single fireball increased from 5 056 kg to 16 432 kg, the duration and maximum diameter of the fireball increased from 6.9 s to 11.3 s and 40 m to 98 m, respectively, which significantly expanded the influence area of thermal radiation. The distribution of evacuees varied nonlinearly over time, resulting in the number of casualties varying nonlinearly with the moment of the fireball formation. The domino effect led to multiple fireballs, and the number of fatalities increased from less than 3 to more than 10, which escalated the accident level from a general accident to a major accident. The results provided theoretical support for the quantitative assessment of accidents consequences of fireballs and other fires.

Key words: fireball in a chemical plant, thermal radiation hazard, quantitative assessment, occupant evacuation, casualty probability