Abstract: The variation of the concentrations of aerosol ¹³¹I,airborne ¹³⁷Cs and ¹³³Xe under 3 different disposal measures,i.e.,without spray and emergency ventilation,with spray but without emergency ventilation,and with spray and emergency ventilation,was analyzed after a large-break LOCA for the small-scale experiment reactor.The results showed that the spray played an effective role in reducing the radioactive concentration of ¹³¹I and ¹³⁷Cs,but almost had no effect on the inert gas ¹³³Xe.Under the condition of this study,when the security system failed,the radioactive material would escape once the core melt.Finally,by the virtual simulation of the accident,the variation of the nuclide radioactive concentration in the whole containment was expressed intuitively in real-time and the combination of the accurate simulation data and the visual interface was achieved in this paper.