Abstract: Instantaneous accidents generally refer to instantaneous radioactive releases or extremely short time radioactive release scenarios. It is not appropriate to adopt the traditional point source dispersion model for continuous release to evaluate the habitability consequence of Main Control Room (MCR). This paper refers to the basic model of instantaneous plume release model and considers the actual design characteristics of nuclear power plants to form an atmospheric dispersion model for evaluating the habitability of MCR under instantaneous accident conditions. The model was utilized based on a typical instantaneous accident. The comparison results with traditional point source dispersion model show that the model formed in this paper can better characterize the release characteristics of such accidents, and the atmospheric dispersion results used for evaluating the habitability of MCR are closely related to the volume of instantaneous accident plume. Additional analysis conducted in this paper indicates that under the same released source terms, the larger the volume of released plume, the lower the radioactive impact on the MCR.

Key words: instantaneous accident, main control room, atmospheric dispersion mode, habitability assessment, point source