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NKS Programme Area:NKS-R
Research Area:Thermal Hydraulics
Report Number:NKS-347
Report Title:Modelling of the Effects of Steam Injection through Spargers on Pool Thermal Stratification and Mixing
Activity Acronym:ENPOOL
Authors:Ignacio Gallego-Marcos, Lukasz Filich, Walter Villanueva, Pavel Kudinov,
Abstract:In a Boiling Water Reactor, steam is discharged into the pressure suppression pool through spargers to protect the primary circuit from over-pressurization. If thermal stratification develops, the pressure suppression capability is reduced. Mixing or stratification of the pool is determined by the interplay between heat and momentum sources generated by the steam condensation. Different momentum can be generated in different condensation regimes, depending on steam mass flux, pool temperature and sparger design. Simulation of Direct Contact Condensation (DCC) is a challenge for contemporary modeling tools, especially for prototypic long-term transients. In previous work, the Effective Heat Source (EHS) and Effective Momentum Source (EMS) models were proposed to simulate thermal stratification and mixing during a steam injection into a large pool of water. These models are (i) computationally efficient, since the small scale phenomena of DCC is not resolved, and (ii) sufficiently accurate, since the integral effects of these phenomena on the large scale pool circulation are taken into account. EHS/EMS models have been developed and validated for blowdown pipes using experimental data from the PPOOLEX facility at LUT. The goal of this work is to develop and validate EHS/EMS models for spargers. The models are implemented in the containment code GOTHIC. To obtain data for validation, a set of experiments are proposed in the PPOOLEX facility using a scaling methodology to ensure that the ranges of important parameters and regimes from the plant scale are addressed in the experiment. Pre-test analysis was carried out in order to (i) confirm the scaling methodology, (ii) provide suggestions for the instrumentation, (iii) get insights about detailed thermal-hydraulic behavior of the pool, and (iv) provide detailed instructions for the test procedures. A preliminary validation against the experiments shows overall good predictive capabilities of the EHS/EMS models. However, it was observed that accurate prediction of the effective momentum for the unstable steam condensation regimes requires further development of the model closures.
Keywords:Thermal Stratification, Mixing, Pressure Suppression Pool, Spargers, Containment, Thermal Hydraulic, GOTHIC, Light Water Reactor
Publication date:19 Aug 2015
ISBN:ISBN 978-87-7893-430-7
Number of downloads:1775
Download:pdf NKS-347.pdf
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