Limiting Factors for External Reactor Vessel Cooling

摘要: The method of external reactor vessel cooling (ERVC) that involves flooding the cavity during a severe accident has been considered viable means for in-vessel retention (IVR). For high-power reactors, however, there are some limiting factors might adversely affect feasibility using ERVC as IVR. In this paper, key have identified and critically discussed. These include choking limit steam venting (CLSV) through bottleneck vessel/insulation structure, critical heat flux (CHF) downward-facing boiling on outer surface, two-phase flow instabilities in natural circulation loop within flooded cavity. To enhance ERVC, it is necessary to eliminate or relax these factors. Accordingly, methods thus improve margins IVR proposed demonstrated, APR1400 an example. strategy based two distinctly different ERVC. One use enhanced design facilitate annular channel. other appropriate coating promote boiling. It found ofmore » with enlargement could greatly process region well streamline resulting motions By selecting suitable design, not only CLSV but also CHF limits be significantly increased. addition, problem associated flow-induced mechanical vibration minimized. coatings made microporous metallic layers surface. With coatings, local at angular locations surface by {approx}1.2 2 times compared plain without coatings. enhancement attributed structure porous itself capillary action induced. matrix cavities voids effectively trap vapor, which serve active nucleation sites. sites turn fed liquid flowing interconnected channels. pores inlets supply heating leading appreciable transfer limits. Results present study suggest utilizing coating, possible minimize instability problems, substantially increasing margin IVR.« less