Characterizing Stratified Flow in Passive Emergency Core Cooling Systems for Advanced Light Water Reactors Project No: DE-FG07-03ID14500

摘要

Experiments performed to evaluate the Generation III Westinghouse AP600 advanced light water reactor (LWR) behavior during loss-of-coolant accidents demonstrated that passive emergency core cooling systems (ECCS), driven by density gradients, inject over a prolonged time period and keep the core covered and cool. When passive ECCS injection is underway the experiments showed that highly-subcooled water enters horizontal piping while a saturated stratified water layer may form part of the free surface. When a free surface is present, steam fills the volume above the free surface. Hence a three-layered system may exist as described in Liou, Schultz, and Kukita, 1997 and shown in Figure 1. These characteristics will likely also be observed in the Generation IV Supercritical Water Reactor (SCWR) passive cooling system. The presence of a subcooled water interface, in contact with steam, is a precursor for condensation-induced water hammer (C1WH), Bjorge & Griffith, 1984. Hence it is crucial that the pipe flow with a free surface, including the counter-current stratified flow phenomena, be intimately understood and accurately modeled.