Passive Containment Cooling System (PCCS) removes residual heat from upper drywell of the containment to the liquid pool surrounding the PCCS heat exchanger. It also has an important role in mitigating the offsite dose by retention of a fission product release in the containment. The operation of the PCCS is based on density differences between the containment and water pool.
To study the behavior of the PCCS configuration planned to be used in the ABWR II concept and to gain experimental data for the validation work of MELCOR severe accident code, a scaled down PCCS model was designed and constructed at Lappeenranta University of Technology in Finland in 2012–2013.
The PCCS model is connected to the drywell and wetwell compartments of PPOOLEX, which is acting as a host facility. Steam needed in the experiments is produced with the nearby PACTEL facility. The PCCS model consists of five horizontal U-tube shaped heat exchange tubes (Ø32.0x1.2, material stainless steel EN 1.4301) installed inside a secondary side liquid pool (volume ~1.4 m3). The pool is in atmospheric pressure and covered by a lid with an exit pipe out of the laboratory and with viewing windows for video cameras. The horizontal length of the tube bundle is about 1700 mm and the lengths of the heat exchange tubes are 3228 mm (tube 1), 3298 mm (tubes 2, 3 and 4) and 3370 mm (tube 5).
On both sides of the heat exchange tubes in the secondary side pool there is a vertical flow controller made of 8 mm thick polycarbonate plate. The distance between the flow controller plates is 238 mm. Condensation water and non-condensables are separated from each other by gravity in the outlet chamber. Condensate is drained from the outlet chamber into the lower part of the PPOOLEX wet well through a DN25 line by gravity. Correspondingly, non-condensables are led from the outlet chamber into the wet well through a DN50 line.
The test facility is equipped with 79 temperature, one pressure, four pressure difference and three flow rate measurements. Measurements of the PPOOLEX facility are, of course, actively used in the experiments with the PCCS model. CCTV system consists of standard video cameras and digital videocassette recorders.
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