ACME Upper Plenum Entrainment Phenomena Scaling Analysis and Criteria

ACME (Advanced Core-cooling Mechanism Experiment) is an integral thermal-hydraulic facility designed to produce data for validating the software that is intended to be used to calculate the behavior of large advanced PWRs in China. Design of ACME is working on now. ACME would simulate the important phenomenon of the reactor cooling system and passive core cooling system of PWR. When the level is lower than the hot leg nozzles, droplets would be carried out by the vapor. This phenomenon is entrainment of upper plenum. Entrainment is a important phenomena in the upper plenum both of prototype and test facility. It would influence the level and inventory of the core. We analyzed entrainment phenomena in the upper plenum through H2TS scaling analysis method [1] based on Ishii’s pool entrainment model [2] in this paper. H2TS scaling analysis method includes two parts: one is the top-down system scaling and the other is the bottom-up process scaling analysis. Ishii’s pool entrainment model define the entrainment as the ratio of the droplet to vapor mass flux and divide three regions by the diameter and velocity of the droplet, including near surface region, momentum controlled region and deposition controlled region. The key scaling criteria and scaling ratios which should be met under ACME design are given for different entrainment regions. Based on these criteria and ratios, ideal upper plenum design of ACME facility will simulate the entrainment phenomena conservatively.