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Gallego-Marcos, IgnacioORCID iD iconorcid.org/0000-0002-5794-2651
Publications (4 of 4) Show all publications
Gallego-Marcos, I., Kudinov, P., Villanueva, W., Kapulla, R., Paranjape, S., Paladino, D., . . . Kotro, E. (2019). Pool stratification and mixing induced by steam injection through spargers: CFD modelling of the PPOOLEX and PANDA experiments. Nuclear Engineering and Design, 347, 67-85
Open this publication in new window or tab >>Pool stratification and mixing induced by steam injection through spargers: CFD modelling of the PPOOLEX and PANDA experiments
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2019 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 347, p. 67-85Article in journal (Refereed) Published
Abstract [en]

Spargers are multi-hole injection pipes used in Boiling Water Reactors (BWR) and Generation III/III+ Pressurized Water Reactors (PWR) to condense steam in large water pools. During the steam injection, high pool surface temperatures induced by thermal stratification can lead to higher containment pressures compared with completely mixed pool conditions, the former posing a threat for plant safety. The Effective Heat Source (EHS) and Effective Momentum Source (EMS) models were previously developed and validated for the modelling of a steam injection through blowdown pipes. The goal of this paper is to extend the EHS/EMS model capabilities towards steam injection through multi-hole spargers. The models are implemented in ANSYS Fluent 17.0 Computational Fluid Dynamics (CFD) code and calibrated against the spargers experiments performed in the PPOOLEX and PANDA facilities, analysed by the authors in Gallego-Marcos et al. (2018b). CFD modelling guidelines are established for the adequate simulation of the pool behaviour. A new correlation is proposed to model the turbulent production and dissipation caused by buoyancy. Sensitivity studies addressing the effect of different assumptions on the effective momentum magnitude, profile, angle and turbulence are presented. Calibration of the effective momentum showed an inverse proportionality to the sub-cooling. Differences between the effective momentum calibrated for PPOOLEX and PANDA are discussed. Analysis of the calculated flow above the cold stratified layer showed that the erosion of the layer is induced by the action of turbulence rather than mean shear flow.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
Thermocline, Turbulence production buoyancy, Richardson, C-3e coefficient, Oscillatory bubble regime
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-251271 (URN)10.1016/j.nucengdes.2019.03.011 (DOI)000465217900008 ()2-s2.0-85063478019 (Scopus ID)
Note

QC 20190514

Available from: 2019-05-14 Created: 2019-05-14 Last updated: 2019-05-29Bibliographically approved
Gallego-Marcos, I., Grishchenko, D. & Kudinov, P. (2019). Thermal stratification and mixing in a Nordic BWR pressure suppression pool. Annals of Nuclear Energy, 132, 442-450
Open this publication in new window or tab >>Thermal stratification and mixing in a Nordic BWR pressure suppression pool
2019 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 132, p. 442-450Article in journal (Refereed) Published
Abstract [en]

The pressure suppression pool of a Nordic Boiling Water Reactor (BWR) serves as a heat sink to condense steam from the primary coolant system in normal operation and accident conditions. Thermal stratification can develop in the pool when buoyancy forces overcome the momentum created by the steam injection. In this case, hot condensate forms a hot layer at the top of the pool, reducing the pool cooling and condensation capacity compared to mixed conditions. The Effective Heat Source and Effective Momentum Source (EHS/EMS) models were previously proposed to model the large-scale pool behavior during a steam injection. In this work, we use CFD code of ANSYS Fluent with the EHS/EMS models to simulate the transient behavior of a Nordic BWR pool during a steam injection through spargers. First, a validation against a Nordic BWR pool test with complete mixing is presented. Prediction of the pool behavior for other possible injection scenarios show that stratification can occur at prototypic steam injection conditions, and that the hot layer temperature above the injection point can be non-uniform. In cases with significant steam condensation inside the sparger pipes, the 95 degrees C pool temperature limit for the Emergency Core Cooling System (ECCS) pumps was reached similar to 7 h after the beginning of the blowdown.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Sparger, Relief vales, Steam injection, Condensation, CFD, Effective momentum
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-259408 (URN)10.1016/j.anucene.2019.04.054 (DOI)000482247600042 ()2-s2.0-85065229097 (Scopus ID)
Note

QC 20190925

Available from: 2019-09-25 Created: 2019-09-25 Last updated: 2019-09-25Bibliographically approved
Gallego-Marcos, I., Kudinov, P., Villanueva, W., Puustinen, M., Räsänen, A., Tielinen, K. & Kotro, E. Effective momentum induced by steam condensation in the oscillatory bubble regime.
Open this publication in new window or tab >>Effective momentum induced by steam condensation in the oscillatory bubble regime
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The spargers used in Boiling Water Reactors (BWR) discharge steam from the primary coolant system into a pool of water. Direct steam condensation in subcooled water creates sources of heat and momentum determined by the condensation regimes, called “effective sources” in this work. Competition between the effective sources can result in thermally stratification or mixing of the pool. Thermal stratification is a safety concern in BWRs since it reduces the steam condensation and pressure suppression capacity of the pool. In this work, we present semi-empirical correlations to predict the effective momentum induced by steam condensation in the oscillatory bubble regime, relevant for the operation of spargers in BWRs. A Separate Effect Facility (SEF) was designed and built at LUT, Finland, in order to provide the necessary data. An empirical correlation for the effective momentum as a function of the Jakob number is proposed. The Kelvin Impulse theory was also applied to estimate the effective momentum based on information about the bubble dynamics. To do this, new correlations for the bubble collapse frequencies, maximum bubble radius, velocities, pressure gradient and heat transfer coefficient are proposed and compared to available data from the literature. The effective momentum induced by sonic steam jets appears to be constant in a wide range of studied Jakob number. However, further experimental data is necessary at larger Jakob numbers and steam mass fluxes.

Keywords
Effective momentum; Kelvin Impulse; bubble radius; collapsing frequency; heat transfer coefficient
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-238704 (URN)
Note

QC 20181109

Available from: 2018-11-08 Created: 2018-11-08 Last updated: 2018-11-12Bibliographically approved
Gallego-Marcos, I., Grishchenko, D. & Kudinov, P. Thermal Stratification and Mixing in a Nordic BWR Pressure Suppression Pool.
Open this publication in new window or tab >>Thermal Stratification and Mixing in a Nordic BWR Pressure Suppression Pool
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The pressure suppression pool of a Nordic Boiling Water Reactor (BWR) serves as a heat sink to condense steam from the primary coolant system in normal operation and accident conditions. Thermal stratification can develop in the pool when buoyancy forces overcome the momentum created by the steam injection. In this case, hot condensate forms a hot layer at the top of the pool, reducing the pool cooling and condensation capacity compared to mixed conditions. The Effective Heat Source and Effective Momentum Source (EHS/EMS) models were previously proposed to model the large-scale pool behavior during a steam injection. In this work, we use CFD code of ANSYS Fluent with the EHS/EMS models to simulate the transient behavior of a Nordic BWR pool during a steam injection through spargers. First, a validation against a Nordic BWR pool test is presented. Prediction of the pool behavior for other possible injection scenarios show that stratification can occur at prototypic steam injection conditions, and that the hot layer temperature above the injection point can be non-uniform. In cases with significant steam condensation inside the sparger pipes, the 95 oC pool temperature limit for the Emergency Core Cooling System (ECCS) pumps was reached ~7 h after the beginning of the blowdown.

Keywords
Sparger; relief vales; steam injection; condensation; CFD; effective momentum
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-238705 (URN)
Available from: 2018-11-08 Created: 2018-11-08 Last updated: 2018-11-12Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5794-2651

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