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Summary of the experimental work at LUT:
In 2012, the behaviour at the vent pipe outlet during air/steam discharge is investigated experimentally. Particle Image Velocimetry (PIV) system and a modern high speed camera have been installed in the PPOOLEX facility in 2011. Experiments on direct-contact condensation are continued in 2012 with an extensive test series, where the potential of the new sophisticated measuring equipment can be comprehensively utilized. The goal of the experiments is to produce CFD grade measurement data of rapid steam condensation processes to be used in the development and validation of simulation tools by VTT.
The second experiment series with the PPOOLEX facility in 2012 will concentrate on providing necessary data for the development of the effective momentum source (EMS) model at KTH. Dynamics and movement of the free water surface in the blowdown pipe will be detected with a fine net of measurements. Six experiments with different steam mass flow rates and transient times will be carried out according to the detailed test plan written by KTH.
Summary of the modelling work at VTT:
In 2012, the CFD model for chugging in pressure suppression pools is further developed. The models for heat transfer and the interphasial area of liquid water and vapour are improved. In CFD modelling, the goal is to obtain correct collapse speeds of vapour bubbles and correct penetration of liquid water in the vent pipes. The new measurements performed at LUT are used for detailed comparison of the calculations to the experiments. CFD simulations of the experiments are performed with improved models, fine mesh and short time step in order to achieve improved resolution in the simulations.
Two-way coupled FSI calculations are performed for PPOOLEX experiments and for a model of a sector of BWR containment. The scaling of the pressure load amplitude and duration from the laboratory experiment to the BWR are studied. The loads in a BWR are considered with an acoustic model of half or full containment, i.e., 8 or 16 vent pipes. Stochastic analysis of the loads originating from multiple vent pipes is used to analyse the loads in the chugging phase. Simulation of the loads in the BWR geometry is performed.
Summary of the modelling work at KTH:
In 2012, the focus of KTH work will be development and validation of new robust and computationally efficient models based on a synthesis of available methods and experimental data with plant design specific considerations. KTH will continue to develop and implement the Effective Heat Source (EHS) and Effective Momentum Source (EMS) models in GOTHIC code. To provide necessary data for the development of the effective momentum source (EMS) model, a series of tests in PPOOLEX facility has been proposed in collaboration with LUT. A finer resolution both in space and time for detection of the dynamics of the free water surface in the blowdown pipe is proposed to get a more accurate estimation of the frequency and amplitude of oscillations for assessment of the effective momentum. The need for new experimental data for determining the model parameters and also for testing the predictive capability of the developed model is explained in the joint proposal for the tests. Systematic validation of the current version and modified GOTHIC code models against latest available data related to BWR pressure suppression pool operation is ongoing.
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