Revision of a CHF correlation for PWR under low pressure conditions with only dimensionless parameters as independent variables
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B. Pang
Abstract
Accurate prediction of the critical heat flux (CHF) is one of the key tasks of PWR core design and safety assessment, for the maximal allowable heat flux in the reactor core is limited by CHF. Since CHF in rod bundle cannot be predicted analytically, up-to-date predictive approach is based on empirical correlations related to the local thermal-hydraulic conditions, geometry and power distribution. However, development of CHF correlation for PWR fuel assemblies under low pressure conditions (2–10 MPa) is constrained by limited amount of experimental data points, which builds up in statistics a typical problem of small sample amounts, but requiring simultaneously high prediction accuracy. In our previous study, stepwise regression method was applied to develop a dimensional, empirical CHF correlation for PWR under low pressure conditions, termed as the advanced low pressure CHF correlation (ALPC), which successfully solves the challenge of small sample problem. However, the ALPC correlation still uses dimensional independent variables with less physical meanings, which limits its physical interpretability. In the current study, stepwise regression method was used to develop a revised, dimensionless version of the ALPC CHF correlation. First, various dimensionless, two-phase thermal-hydraulic parameters that might influence CHF were selected as candidate independent variables. With stepwise regression, the form and coefficients of the revised CHF correlation were optimized in a dynamic manner. Compared to the current ALPC correlation, the revised version developed in this study possesses a similar simple form but a much higher prediction accuracy. Revision of the ALPC correlation demonstrates clearly the advantages of utilizing dimensionless parameters as independent variables in CHF correlation, which points out a new direction of developing rod-bundle CHF correlations for engineering purpose.
Kurzfassung
Die genaue Vorhersage der kritischen Wärmestromdichte (CHF) ist eine der Hauptaufgaben des DWR-Kerndesigns und der Sicherheitsbewertung, denn die maximal zulässige Wärmestromdichte im Reaktorkern wird durch CHF begrenzt. Da CHF im Stabbündel nicht analytisch vorhergesagt werden kann, basiert der aktuelle Ansatz auf empirischen Korrelationen in Bezug auf die lokalen thermohydraulischen Bedingungen, die Geometrie und die Leistungsverteilung. Die Entwicklung der CHF-Korrelation für DWR-Brennelemente unter Niederdruckbedingungen (2–10 MPa) wird jedoch durch eine begrenzte Anzahl von experimentellen Datenpunkten eingeschränkt, was in der Statistik ein typisches Problem kleiner Probenmengen aufbaut, aber gleichzeitig eine hohe Vorhersagegenauigkeit erfordert. In unserer vorherigen Studie wurde die schrittweise Regressionsmethode angewendet, um eine dimensionale, empirische CHF-Korrelation für DWR unter Niederdruckbedingungen zu entwickeln, die als Advanced Low Pressure CHF Correlation (ALPC) bezeichnet wird und die die Herausforderung des kleinen Probenproblems erfolgreich löst. Die ALPC-Korrelation verwendet jedoch immer noch dimensionale unabhängige Variablen mit weniger physikalischen Bedeutungen, was ihre physikalische Interpretierbarkeit einschränkt. In der aktuellen Studie wurde mit der schrittweisen Regressionsmethode eine überarbeitete, dimensionslose Version der ALPC CHF-Korrelation entwickelt. Zunächst wurden verschiedene dimensionslose, zweiphasige thermohydraulische Parameter, die den CHF beeinflussen könnten, als unabhängige Variablen ausgewählt. Bei der schrittweisen Regression wurden Form und Koeffizienten der revidierten CHF-Korrelation dynamisch optimiert. Im Vergleich zur aktuellen ALPC-Korrelation weist die in dieser Studie entwickelte überarbeitete Version eine ähnlich einfache Form, aber eine wesentlich höhere Vorhersagegenauigkeit auf. Die Überarbeitung der ALPC-Korrelation zeigt deutlich die Vorteile der Verwendung dimensionsloser Parameter als unabhängige Variablen in der CHF-Korrelation, was eine neue Richtung der Entwicklung von Stabbündel-CHF-Korrelationen für den Einsatz in der Energiewirtschaft aufzeigt.
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© 2019, Carl Hanser Verlag, München
Articles in the same Issue
- Contents/Inhalt
- Contents
- Technical Contributions/Fachbeiträge
- Revision of a CHF correlation for PWR under low pressure conditions with only dimensionless parameters as independent variables
- Experimental study on transient flow fluctuation characteristics in a 3 × 3 rod bundle under rolling condition
- The core shroud leakage analysis and study for Kuosheng nuclear power plant
- Coupling simulation of neutron kinetics core model with CFD of IPWR steam line break accident
- Numerical prediction of single-phase flow mixing characteristics in a 1/12th of the cross segment of a 54-rod bundle
- 10.3139/124.110984
- Control rod material effect on safety parameters of research reactors
Articles in the same Issue
- Contents/Inhalt
- Contents
- Technical Contributions/Fachbeiträge
- Revision of a CHF correlation for PWR under low pressure conditions with only dimensionless parameters as independent variables
- Experimental study on transient flow fluctuation characteristics in a 3 × 3 rod bundle under rolling condition
- The core shroud leakage analysis and study for Kuosheng nuclear power plant
- Coupling simulation of neutron kinetics core model with CFD of IPWR steam line break accident
- Numerical prediction of single-phase flow mixing characteristics in a 1/12th of the cross segment of a 54-rod bundle
- 10.3139/124.110984
- Control rod material effect on safety parameters of research reactors
