Scaling Analysis of Fluid Properties for Natural Circulation Phenomena Under Station Blackout Accident

Abstract

Station blackout accidents increasingly become the focus of research in the field of nuclear safety after Japan’s Fukushima nuclear plant accident in March 2011. Core decay heat under station blackout condition will be transferred by natural circulation occurring in passive systems for the nuclear plants incorporated through passive safety design concept such as AP1000 or CAP1400. As a result, response of safety systems will differ in accident sequence and kind between passive safety plant and traditional plant. The safety need that characteristics of passive safety plant should be verified through integral experiment facility makes scaling analysis important in design or modification of experiment facility. Scaling of natural circulation in passive system under station blackout accident is investigated analytically in this paper. The analytical model for circulation velocity is established by proper hypothesis and simplification. The similarity criteria that should be preserved between test facility and prototype are finally obtained from governing equations which are non-dimensionalized using steady-state solution, initial or boundary condition. The results show that Richardson number, Friction number, Source number, and Heat Capacity number are the similarity criteria and the deriving requirements for test facility. In operating parameter scope for PRHR system, the properties similarity could be approximately achieved using same fluid in low-pressure facility.