Application of release starting time classification for planning emergency preparedness and response to the hypothetical accident scenario of iPWR-SMR in Thailand.

• Uncertainty analysis of source term reflected latent peaks of release starting time. • Release starting time is classified to support a flexible SMR emergency plan via GMM. • Dose level for SMR main emergency action is limited to 1 mSv zone within 6 km radius. • Chance of late release starting time is used to set backup emergency plans for SMR. Due to the interest in SMR reactors in newcomer countries, the understanding of the risk of source term release and dose exposure of SMR technology is important scientific data for communicating between the government and people. This study aims to extend the application of release starting time classification of level 2 PSA in SMR technology to inform strategic planning for nuclear consequences and determine size requirements for the emergency planning zones in level 3 PSA. The SBO accident scenario of iPWR at the location in the Ubon Ratchathani province, Thailand, was investigated in this study. The GMM is used to classify the probability density of uneven distributions of release starting times into the two groups. The higher probability density and maximum radioactive release in Group (1) were used to suggest the main plan for emergency response. In the main plan, the local government needs to evacuate the people outside 6 km to avoid dose exposure if source term release is monitored within 8–21 h. The impact of source term release in Group (2) was set as a backup plan for considering an emergency planning extension if the time delay to later than 21 h. Finally, the nuclear consequences of SMRs are compared with large NPPs in the same accident scenarios. SMR technology has the potential to support flexible emergency planning zones for sheltering and evacuation without significant dose exposure to neighboring countries. [ABSTRACT FROM AUTHOR]