Scaling analysis of AP1000 ADS-4 entrainment and depressurization

•A comprehensive scaling method in vertical up branch entrainment was developed.•A system depressurization scaling method in small break LOCA was developed.•We improved the upper plenum entrainment scaling method based on previous work.•The scaling ratios were determined and used in the design of the test loop.

ADS-4 is an important passive safety feature in AP1000 design which provides a controlled depressurization. In this paper, reduced diameter and height scaling analysis with identical fluid properties was conducted on AP1000 ADS-4 blowdown and depressurization process. The scaling analysis consisted of ADS-4 branch line entrainment scaling, system depressurization scaling and upper plenum entrainment scaling. Reasonable dimensionless criteria of related thermal hydraulic phenomena were chosen and developed by analyzing conservation equations. Experimental geometric dimensions and operating conditions for the scaled test facility were obtained.