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Pool stratification and mixing during a steam injection through spargers: analysis of the PPOOLEX and PANDA experiments
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering.ORCID iD: 0000-0002-5794-2651
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering.ORCID iD: 0000-0002-0683-9136
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
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2018 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 337, p. 300-316Article in journal (Refereed) Published
Abstract [en]

Spargers are multi-hole injection pipes used in Boiling Water Reactors (BWR) and Advanced Pressurized (AP) reactors to condense steam in large water pools. A steam injection induces heat, momentum and mass sources that depend on the steam injection conditions and can result in thermal stratification or mixing of the pool. Thermal stratification reduces the steam condensation capacity of the pool, increases the pool surface temperature and thus the containment pressure. Development of models with predictive capabilities requires the understanding of basic phenomena that govern the behavior of the complex multi-scale system. The goals of this work are (i) to analyze and interpret the experiments on steam injection into a pool through spargers performed in the large-scale facilities of PPOOLEX and PANDA, and (ii) to discuss possible modelling approaches for the observed phenomena. A scaling approach was developed to address the most important physical phenomena and regimes relevant to prototypic plant conditions. The focus of the tests was on the low steam mass flux and oscillatory bubble condensation regimes, which are expected during a long-term steam injection transient, e.g. in the case of a Station Black Out (SBO). Exploratory tests were also done for chugging and stable jet conditions. The results showed a similar behavior in PPOOLEX and PANDA in terms of jet induced by steam condensation, pool stratification, and development of hot layer and erosion of the cold one. A correlation using the Richardson number is proposed to model the erosion rate of the cold layer as a function of the pool dimensions and steam injection conditions.

Place, publisher, year, edition, pages
Elsevier, 2018. Vol. 337, p. 300-316
Keywords [en]
Pool stratification, Oscillatory bubble, Thermocline erosion, Richardson, Turbulence, Chugging
National Category
Energy Systems
Identifiers
URN: urn:nbn:se:kth:diva-232461DOI: 10.1016/j.nucengdes.2018.07.004ISI: 000441759300026Scopus ID: 2-s2.0-85050149931OAI: oai:DiVA.org:kth-232461DiVA, id: diva2:1234259
Funder
Swedish Radiation Safety Authority
Note

QC 20180822

Available from: 2018-07-23 Created: 2018-07-23 Last updated: 2018-11-09Bibliographically approved
In thesis
1. Steam condensation in a water pool and its effect on thermal stratification and mixing
Open this publication in new window or tab >>Steam condensation in a water pool and its effect on thermal stratification and mixing
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Pressure Suppression Pool (PSP) of a Boiling Water Reactor (BWR) is a large heat sink designed to limit the containment pressure by condensing steam released from the primary coolant system. The development of thermal stratification is a safety concern since it leads to higher containment pressures than in completely mixed conditions, and can affect the performance of systems such as the emergency core cooling and containment spray, which the use PSP as a source of water.The goal of this thesis is to develop and validate models for the prediction of the PSP behavior during a steam injection in a Nordic BWR. The framework of the Effective Heat Source and Effective Momentum Source (EHS/EMS) models is used to provide the integral heat and momentum sources induced by the steam condensation. The EHS/EMS can be implemented in a containment thermal-hydraulic or a CFD code, where the pool is modelled with a single-phase liquid solver.EHS/EMS models are developed for the low steam mass flux regimes appearing in (i) large diameter blowdown pipes connecting the drywell to the wetwell pool; and (ii) multi-hole sparger pipes connecting the primary system to the pool.Empirical correlations are developed to predict the effective momentum induced by chugging in the blowdown pipes. The correlations are implemented in GOTHIC, where a containment model is proposed to enable capturing the feedback between pool conditions and drywell pressure. Validation is performed against the PPOOLEX experiments.Conceptual designs are proposed for a set of large-scale pool experiments with spargers in the PPOOLEX and PANDA facilities. Correlations are proposed for the erosion velocity of a cold layer, and ranges are estimated for the angle, profile and turbulence of the momentum sources created by steam injection. CFD simulations of the experiments is done to calibrate the momentum sources in the oscillatory bubble regimes. A concept of the Separate Effect Facility (SEF) is proposed to provide a measurements of the effective momentum. Empirical correlations for the bubble radius, velocity, heat transfer coefficient, etc. are also developed and compared to available data from the literature.Application of the developed CFD and EHS/EMS models to full-scale containment behavior shows that thermal stratification can occur during prototypic steam injection conditions. Recommendations are given on how to avoid this.

Place, publisher, year, edition, pages
Sweden: KTH Royal Institute of Technology, 2018. p. 69
Series
TRITA-SCI-FOU ; 2018:48
Keywords
Steam injection, EHS/EMS, blowdown pipes, spargers, chugging, oscillatory bubble, CFD, condensation pool, stratification, mixing
National Category
Energy Engineering
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-238732 (URN)978-91-7873-028-5 (ISBN)
Public defence
2018-12-07, FB54, AlbaNova University Centre, Rogslagstullbacken 21, 114 21 Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Swedish Radiation Safety Authority
Note

QC 20181109

Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2018-11-12Bibliographically approved

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