This report summarizes the results of the sparger experiments carried out with the scaled down PPOOLEX test facility designed and constructed at Lappeenranta University of Technology. Steam was blown through the vertical DN65 sparger type blowdown pipe to the condensation pool filled with sub-cooled water.
The main objective of the experiments was to obtain verification data for the development of the Effective Momentum Source (EMS) and Effective Heat Source (EHS) models to be implemented in GOTHIC code by KTH. A detailed test matrix and procedure put together on the basis of the pre-test calculations was provided by KTH.
Altogether five experiments were carried out. The experiments consisted of two stratification periods and two mixing periods.
During the first stratification period a 120–130 g/s steam flow rate was used. With this flow rate steam flowed through the injection holes of the sparger head as small jets and condensed mainly outside the sparger pipe. As a result temperatures remained constant below the blowdown pipe outlet but increased towards the pool surface layers indicating strong thermal stratification of the wetwell pool water. In the end of the first stratification period the temperature difference between the pool bottom and surface was 18–26 ºC depending on the test in question. In the second stratification period a 70–97 g/s steam flow rate was used. In the end of this period the temperature difference between the pool bottom and surface was 20–31 ºC.
During the mixing periods I and II the steam flow rate was increased rapidly to 130–260 g/s or decreased to 40–70 g/s to mix the pool water inventory. Total mixing of the pool was not obtained in every experiment. Mixing efficiency depended on the flow mode in question i.e. on the used steam mass flow rate and on the pool bulk temperature. Enough turbulence to mix the pool could be created either with high steam flow rates causing strong internal circulation in the pool or with quite small steam flow rates (in the range of 70 g/s) causing external chugging phenomenon at the sparger head. With the intermediate flow rates only the elevations above and a short distance below the sparger head could be mixed. When the flow rate was very low (in the range of 40 g/s) condensation took place inside the sparger pipe and there was no mixing effect at all.
condensation pool, steam blowdown, sparger, mixing