In the event of a core melt accident, pools of water located outside of the reactor pressure vessel will flood the lower part of the reactor cavity outside the pressure vessel. The pools are located above the pressure suppression chamber and are approximately two-thirds full of water. They are physically separated from each other by four equipment compartments containing mechanical components, piping and ventilation equipment. Each pool houses an emergency condenser, a containment cooling condenser (above the water surface), a core flooding line connection, and the SRV discharge pipes with steam quenchers (see Fig. XI-3 to XI-5). In addition, a drywell flooding line leads to the bottom of the drywell for cooling the exterior of the reactor pressure vessel.

XI — 5. Conclusions

In the past, different investigations concerning the emergency cooling were done. Besides the R&D work of FRAMATOME an experimental testing program was conducted at other German and European research centers to provide verification of the mode of operation and effectiveness of the SWR 1000’s passive safety systems. During 1996-1998 the European Union supported the BWR R&D Cluster of innovative passive safety systems, where the FZ Julich, Germany, the GRS Cologne, Germany, the NRG Petten, The Netherlands, NRG Arnheim, The Netherlands, PSI, Switzerland, SIET Piacenca, Italy, STORK NUCON, The Netherlands and VTT Espoo, Finland were involved.

Two large test facilities (NOKO, FZ Julich for separate effect tests and PANDA, PSI for integral tests) delivered experimental data. In addition operational data from the Doodewaard NPP were used. Post­test calculations were performed using system codes: ATHLET, RELAP and TRAC; lumped parameter codes such as COCOSYS, RALOC and GOTHIC. The CFD-codes applied were CFX and PHOENIX.

During the single effect tests, the heat transfer capability of the emergency condensers and the containment cooling condensers were investigated thoroughly. Special attention was directed to the simulation of condensation in horizontal tubes and to 3D stratification phenomena in the surrounding pools.