The In-containment Refueling Water Storage Tank (IRWST) is a newly adopted system in the design of the Advanced Pressurized Reactor (APR)-1400 in Korea. The key function of IRWST of interest is to condense the steam released from the pressurizer through Pilot Operated Safety Relief Valves (POSRV) through "sparger" to the water in the tank under the accident condition. The integrity of the piping system and the IRWST in which the spargers are submerged is strongly dependent on the hydrodynamic loads induced by the POSRV and IRWST operation. In the present study, a regulatory approach to determine the local pool temperature limit specific to the APR-1400 is discussed. The approach is based on the similarity in function and structure between the IRWST and BWR (Boiling Water Reactors) suppression pool while considering the difference in quencher configuration. The criteria on the local temperature limit in BWR suppression pool, the related event analysis scope, and the analysis assumptions are reviewed for providing a background of the criteria for the APR-1400 IRWST. The detailed design of APR-1400 IRWST is reviewed and the related accident analyses are investigated. The applicability of the BWR criteria, accident analysis scope, and assumption in analysis are also investigated. As a result, it is found that maximum local temperature, 366.5 K (200°F), is an applicable limit during the all accident conditions of APR-1400 IRWST. The scope of event analysis can be equivalently matched to those events in BWR, however, the assumptions in analysis of total loss of feedwater (TLOFW) needs further study due to its nature of beyond design basis accident. Local-to-bulk temperature difference also should be incorporated into the criteria such that the temperature difference should be determined by the current computational fluid dynamic (CFD) capability directly and the sufficient verification should be provided.
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