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| NKS Programme Area: | NKS-R | | Research Area: | Thermo hydraulics | | Report Number: | NKS-168 | | Report Title: | Steam Line Rupture Experiments with the PPOOLEX Test Facility | | Activity Acronym: | POOL | | Authors: | Jani Laine, Markku Puustinen | | Abstract: | The results of the steam line rupture experiment series in 2007 with the scaled down PPOOLEX test facility designed and constructed at Lappeenranta University of Technology are reported. The test facility is a closed stainless steel vessel divided into two compartments, dry well and wet well. Air was blown into the dry well compartment and from there through a DN200 blowdown pipe to the condensation pool. Altogether five experiments, each consisting of several blows (tests), were carried out.
The main purpose of the experiment series was to study the initial phase of a postulated steam line break accident inside a BWR containment. Specifically, thermal stratification in the dry well compartment and ejection of water plug from the blowdown pipe were of interest. In addition, the effect of counterpressure on bubble dynamics was studied.
A temperature difference of approximately 15 °C between the upper and lower part of the dry well was measured. In the wet well gas space, a temperature difference of more than 30 °C was registered. These were measured during the compression period of the tests. Towards the end of the tests the temperature differences tended to disappear. To get a more detailed picture of temperature distribution in the wet well, especially close to the water level, a dense net of measurements is required in future experiments. In longer experiments, heat conduction to structures and heat losses to surroundings should also be taken into account.
Ejection of water plugs from the blowdown pipe did not cause notable loads to the structures due to the suppressing effect of the dry well compartment. The maximum measured pressure pulse at the pool bottom was only 10 kPa and the maximum strain amplitude at the pool bottom rounding was negligible both in axial and circumferential direction.
As the counterpressure of the system increased, but the flow rate remained the same, the maximum size of the air bubbles at the blowdown pipe outlet got smaller and smaller. Furthermore, the magnitude of pressure oscillations in the wet well pool decreased with increasing counterpressure. Correspondingly, the formation frequency of bubbles increased with increasing counterpressure. Meanwhile, flow rate had no effect on the bubble formation frequency. | | Keywords: | Condensation pool; steam/air blowdown; non-condensable gas; steam line rupture | | Publication date: | 01 Jul 2008 | | ISBN: | ISBN: 978-87-7893-233-4 | | Number of downloads: | 3716 | | Download: |  NKS-168.pdf |
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